WINSTAR COMMUNICATIONS INC
8-K/A, 1999-02-03
TELEPHONE COMMUNICATIONS (NO RADIOTELEPHONE)
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                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                 --------------

                                 AMENDMENT NO. 2
                                  TO FORM 8-K
                                       ON
                                    FORM 8-K/A

                                 CURRENT REPORT

                     PURSUANT TO SECTION 13 OR 15(D) OF THE
                         SECURITIES EXCHANGE ACT OF 1934


        Date of Report (Date of earliest event reported) November 9, 1998


                          WINSTAR COMMUNICATIONS, INC.
               (Exact Name of Registrant as Specified in Charter)



         Delaware                   1-10726                 13-3585278
- ----------------------------        ----------            -----------------
(State or Other Jurisdiction       (Commission           (IRS Employer
    of Incorporation)              File Number)          Identification No.)




230 Park Avenue, New York, New York                              10169   
- ----------------------------------------                    -------------
(Address of Principal Executive Offices)                      (Zip Code)



Registrant's telephone number, including area code    (212) 584-4000



                                 Not Applicable
          ------------------------------------------------------------
          (Former Name or Former Address, if Changed Since Last Report)



                             Exhibit Index -- Page 4



<PAGE>




ITEM 5.  OTHER EVENTS

         Purchase  of  IRU from Williams.  On December 17, 1998, our subsidiary,
WinStar Wireless,  Inc., entered into an agreement with Williams Communications,
Inc. to purchase from Williams a 25-year  indefeasible  right of use ("IRU") for
four strands of fiber optic cable on a national  route of 14,684  miles  (58,736
fiber miles) and a seven-year option to purchase two additional strands over the
same route  (29,638  fiber  miles).  This fiber  capacity is being  delivered as
routes are built and is expected to be completely  available by the end of 2001,
until  which time  Williams  will  fulfill  substantially  all of our  long-haul
transport  requirements  at no  additional  cost  to us.  We will  pay  Williams
approximately  $640  million over the next seven years for the IRU, the capacity
option,  certain  long-haul  transport and other network assets. We can exercise
the  capacity  option for  approximately  $51  million  payable  in cash  and/or
services.

         Sale of IRU to Williams.  On December 17, 1998, WinStar Wireless,  Inc.
and Williams entered into an agreement  providing for the sale by us to Williams
of a 25-year IRU for up to 2% of our current and future  local  Wireless  FiberK
capacity in the United  States.  Williams will pay us $400 million for this IRU,
with  payments  due ratably as we  construct  up to 270 hub sites.  We expect to
complete  construction  of at least  270 hub  sites  over the next  four  years.
Williams  will also pay us at least  $45.6  million  over a ten-year  period for
network maintenance services that we will provide over the term of the IRU.

         Purchase of Spectrum from CellularVision. On November 9, 1998, pursuant
to  an  Agreement  to  Purchase  LMDS  License   ("Purchase   Agreement")   with
CellularVision  USA,  Inc.  ("CVUSA")  and  CellularVision  of  New  York,  L.P.
("CVNY"),  dated July 10, 1998,  we purchased  from CVNY 850 MHz of the spectrum
covered by the LMDS A Block License issued to CVNY by the Federal Communications
Commission for the New York Primary Metropolitan Statistical Area for a purchase
price of  $32,500,000,  payable in cash.  The 850 MHz  portion of  spectrum  was
disaggregated by CVNY from the remaining spectrum covered by its license.


ITEM 7.  FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS.

   (c)   EXHIBITS:

          10.1 IRU  Agreement  between  WinStar  Wireless,   Inc.  and  Williams
               Communications, Inc. Dated December 17, 1998 (Long-Haul).

          10.2 Wireless Fiber/sm IRU Agreement By and Between WinStar Wireless,
               Inc. and Williams Communications, Inc. Effective as of December
               17, 1998.

          10.3 Agreement  to Purchase  LMDS  License  dated July 10, 1998 by and
               between WinStar  Communications,  Inc.,  CellularVision USA, Inc.
               and CellularVision of New York, L.P.




                                        2
<PAGE>


                                    SIGNATURE


         Pursuant to the  requirements  of the Securities  Exchange Act of 1934,
the  registrant  has duly  caused  this report to be signed on its behalf by the
undersigned hereunto duly authorized.

Date:    February 2, 1999

                                            WINSTAR COMMUNICATIONS, INC.

                                                  /s/ Timothy R. Graham
                                            By: ____________________________ 
                                                Timothy R. Graham
                         
                                       3
<PAGE>


         EXHIBIT INDEX


Exhibit   Document                                                       
- -------   ---------                                                      

  10.1    IRU   Agreement   between   WinStar   Wireless,   Inc.   and  Williams
          Communications, Inc. Dated December 17, 1998 (Long-Hand).

  10.2    Wireless Fiber/sm IRU Agreement By and Between WinStar Wireless, Inc.
          and Williams Communications, Inc. Effective as of December 17, 1998.

  10.3    Agreement to Purchase  LMDS License dated July 10, 1998 by and between
          WinStar Communications, Inc., CellularVision USA, Inc. and 
          CellularVision of New York, L.P.





                                       4

<PAGE>


                                                 Confidential - WinStar/Williams


                                  IRU AGREEMENT

                                     BETWEEN

                             WINSTAR WIRELESS, INC.

                                       AND

                          WILLIAMS COMMUNICATIONS, INC.


                             Dated December 17, 1998


                                   (Long-Haul)



<PAGE>


                                TABLE OF CONTENTS

1.   DEFINITIONS...........................................................1

2.   CONVEYANCE OF DARK FIBER IRUS AND GRANT OF OPTION.....................7
2.1.   Grant of Network IRU................................................7
2.2.   Option..............................................................8
2.3.   Financing Arrangements..............................................8
2.4.   Preferred Provider Status...........................................8
2.5.   Most Favored Customer Provision.....................................9
2.6.   No Title to Realty or Personalty....................................9

3.   CONSIDERATION FOR IRUS................................................10
3.1.   Contract Price......................................................10
3.2.   Exercise Price......................................................10

4.   CONSTRUCTION..........................................................10
4.1.   Construction Representations, Warranties and Covenants..............10
4.2.   Delivery of System Segments.........................................10
4.3.   Renewal of Required Rights..........................................11
4.4.   As-Built Drawings...................................................11
4.5.   Third-Party Consents................................................11

5.   ORDERING AND PROVISIONING.............................................12
5.1.   Provision of Interim Service........................................12
5.2.   Service Orders for Interim Services.................................12
5.3.   Changes in Service Parameters.......................................14
5.4.   Assignment and Assumption of Backbone Agreements....................15

6.   CONNECTION TO THE SYSTEM AND COLLOCATION..............................17
6.1.   Collocation.........................................................17
6.2.   Interconnection.....................................................17
6.3.   Ancillary Services..................................................18

7.   ACCEPTANCE AND TESTING OF FIBERS......................................18
7.1.   Overview............................................................18
7.2.   SSPFAT by Williams..................................................19
7.3.   SSPFAT by WinStar...................................................19
7.4.   Failure Notice......................................................20
7.5.   Correction..........................................................20
7.6.   Testing by Third Party..............................................20
7.7.   System Segment Fiber Acceptance Testing and Acceptance Date.........21
7.8.   Testing of Option Fibers............................................21

8.   USE OF THE SYSTEM.....................................................21
8.1.   Use of WinStar Fibers...............................................21
8.2.   Notice of Damage....................................................21
8.3.   Precautions.........................................................21
8.4.   Use of Equipment....................................................22
8.5.   Liens...............................................................22

9.   TERM..................................................................22
9.1.   Agreement Term......................................................22
9.2.   IRU Terms...........................................................22
9.3.   Effect of Termination...............................................22

<PAGE>

10.  OPERATION, MAINTENANCE, AND REPAIR OF THE SYSTEM......................23
10.1.  Routine Maintenance.................................................23
10.2.  Non-Routine Maintenance.............................................23
10.3.  Subcontractors......................................................23
10.4.  Continued Breach of  Routine Maintenance Obligations................23
10.5.  WinStar Equipment...................................................23
10.6   Access to Systems...................................................23

11.  RELOCATION............................................................24
11.1.  Relocation..........................................................24
11.2.  Cost of Relocation..................................................24
11.3.  Updated As-Built Drawings...........................................24

12.  INVOICING AND PAYMENT.................................................25
12.1.  Due Date and Invoice................................................25
12.2.  Form of Payment.....................................................25
12.3.  Disputed Charges....................................................25
12.4.  Late Interest.......................................................26
12.5.  Adjustments.........................................................26

13.  DISCLAIMER OF WARRANTIES..............................................26
13.1.  Parties.............................................................26
13.2.  Facility Owners/Lenders.............................................26

14.  AUDIT RIGHTS..........................................................26

15.  INDEMNIFICATION.......................................................27
15.1.  Indemnification.....................................................27
15.2.  Third Party Claims..................................................27
15.3.  Indemnification of Providers........................................28
15.4.  WinStar Customers...................................................28

16.  LIMITATION OF LIABILITY...............................................28
16.1.  General Intent......................................................28
16.2.  Liability Restrictions..............................................28
16.3.  Released Parties....................................................29

17.  INSURANCE.............................................................29
17.1.  Insurance...........................................................29
17.2.  Documentation.......................................................30
17.3.  Certificates........................................................30
17.4.  Blanket Policies....................................................30

18.  TAXES AND GOVERNMENTAL FEES...........................................30
18.1.  Payment by WinStar..................................................30
18.2.  Payment by Williams.................................................31
18.3.  Reimbursement.......................................................31
18.4.  Cooperation.........................................................31
18.5.  Services............................................................31

19.  NOTICE................................................................31

20.  CONFIDENTIALITY.......................................................32
20.1.  Confidential Information............................................32
20.2.  Obligations.........................................................32
20.3.  Exclusions..........................................................33
20.4.  No Implied Rights...................................................34

21.  DEFAULT...............................................................34

22.  FORCE MAJEURE.........................................................34
22.1.  Excusable Delay.....................................................34
22.2.  Notice and Remedy...................................................35
<PAGE>
23.  REMEDIES AND DISPUTE RESOLUTION.......................................35
23.1.  Dispute Resolution..................................................35
23.2.  Cumulative Remedies.................................................35
23.3.  Informal Dispute Resolution.........................................35
23.4.  Arbitration.........................................................36
23.5.  Continued Performance...............................................38
23.6.  Immediate Injunctive Relief.........................................38

24.  GENERAL...............................................................38
24.1.  Rules of Construction...............................................38
24.2.  Assignment..........................................................40
24.3.  Relationship of the Parties.........................................42
24.4.  Prohibition on Improper Payments....................................42
24.5.  Entire Agreement; Amendment; Execution..............................42

25.  REPRESENTATIONS, WARRANTIES AND COVENANTS.............................43
25.1.  Representations and Warranties......................................43
25.2.  Additional Williams Covenants.......................................43
25.3.  Infringement of Intellectual Property Rights........................44

26.  USE OF TELECOMMUNICATIONS AND OTHER SERVICES..........................44
26.1.  Condition to Provision of Services..................................44
26.2.  Intrastate Interexchange Services...................................44
26.3.  WinStar Responsibilities............................................45
26.4.  Consents............................................................45
26.5.  Restriction of Transmissions........................................45
26.6.  Reasonableness, Consents and Approval...............................45

                                    EXHIBITS

Exhibit A     Williams System
              Part 1 -- Route Map
              Part 2 -- System Segments
Exhibit B     Williams Network Pricing Schedules and Technical Specifications
Exhibit C     Collocation Provisions
              Part 1 - Transmission Sites
              Part 2 - POPs
Exhibit D     Fiber Splicing, Testing, and Acceptance Standards
Exhibit E     Fiber Specifications
Exhibit F     Cable Installation Specifications
Exhibit G     Transmission Site Specifications
Exhibit H     As-Built Drawing Specifications
Exhibit I     Operations Specifications
Exhibit J     Intentionally omitted
Exhibit K     Payment Terms
Exhibit L     Intentionally Omitted
Exhibit M     Intentionally Omitted
Exhibit N     Intentionally Omitted
Exhibit O     Williams Cities and Location of POPs



<PAGE>


                                  IRU AGREEMENT
                                   (Long-Haul)

         THIS IRU  AGREEMENT  (including  the  Exhibits and  Schedules  attached
hereto,  this "Agreement") is made as of the Effective Date (hereafter  defined)
by and between WINSTAR WIRELESS, INC. ("WinStar"), a Delaware corporation having
its principal  office at 230 Park Avenue,  New York City, New York, and WILLIAMS
COMMUNICATIONS,  INC. ("Williams"), a Delaware corporation, having its principal
office at One Williams Center, Tulsa, Oklahoma 74172.


                              W I T N E S S E T H:


         WHEREAS, Williams has constructed or will construct or obtain rights of
use in a fiber optic communication  system (the "System") located  approximately
along the routes  depicted in Exhibit A, Part 1 (the "Route") and  consisting of
the System Segments, as defined below; and


         WHEREAS, WinStar desires to acquire from Williams, and Williams desires
to provide  to  WinStar,  the  Network  IRU as defined  below upon the terms and
conditions set forth below;


         NOW, THEREFORE, in consideration of the mutual promises set forth below
and other good and valuable  consideration,  the  sufficiency of which is hereby
acknowledged, the parties hereby agree as follows:

1.       DEFINITIONS
         Capitalized  terms and phrases  used in this  Agreement  shall have the
following meanings:  

          (a)  "Acceptance Date" means the date defined in Section 7.7 below.

          (b)  "Acceptance Standards" means the standards set forth in Exhibit D
               with  respect  to  the  testing  of  the  WinStar   Fibers.   

          (c)  "Additional Services" means telecommunications services in excess
               of the Minimum  Commitment,  such  excess is not  included in the
               Contract Price.

          (d)  "Affiliate"  means, with respect to any entity,  any other entity
               Controlling,  Controlled  by or under  common  Control  with such
               entity,  whether  directly  or  indirectly  through  one or  more
               intermediaries.

          (e)  "Agreement"  has the  meaning  set forth in the  preamble to this
               document.  

          (f)  "Ancillary  Collocation  Services"  has the  meaning set forth in
               Exhibit C, Part 1, Section 1(d).

          (g)  "Ancillary Services" has the meaning set forth in Section 6.3.

          (h)  "Assignment  Agreement  Effective Date" has the meaning set forth
               in Section 5.4(a).

          (i)  "Assumed  Backbone  Agreement"  means a Backbone  Agreement  that
               WinStar assigns to Williams in accordance with Section 5.4.

                                       2

<PAGE>

          (j)  "Backbone  Agreements" means the agreements designated by WinStar
               that  WinStar  is a party to as of the  Effective  Date and which
               WinStar  intends to assign to Williams or have  Williams act as a
               payment agent.

          (k)  "Backbone  Agreement  Service  Provider"  means each  provider of
               telecommunications  services  (other than WinStar) who is a party
               to a Backbone Agreement.

          (l)  "Cable"  means  fiber  optic  cable  installed  pursuant  to this
               Agreement as part of the System (including any replacement cable)
               and fibers contained  therein,  including the WinStar Fibers, and
               associated  splicing  connections,  splice boxes and vaults,  and
               conduit.

          (m)  "Circuit" means a communications path with a specified bandwidth.

          (n)  "Claim" means any claim,  action,  dispute,  or proceeding of any
               kind between  WinStar (or any of its  Affiliates,  successors  or
               assigns) and Williams (or any of its Affiliates,  successors,  or
               assigns)  and any other  claim,  transaction,  occurrence,  loss,
               liability,  expense or other matter arising out of, in connection
               with, or in any way related to, the Network IRU, the System, this
               Agreement or any other  instrument,  arrangement or understanding
               related to the Network IRU.

          (o)  "Claimant" has the meaning set forth in Section 15.1.
               

          (p)  "Collocation  Service"  has the  meaning  set forth in Exhibit C,
               Part 2.


          (q)  "Connecting  Point" means a point where the network or facilities
               of WinStar will connect to the System.

          (r)  "Contract Price" has the meaning set forth in Section 3.1.

          (s)  "Control" and its derivatives mean legal, beneficial or equitable
               ownership,  directly or  indirectly,  of more than fifty  percent
               (50%) of the outstanding voting capital stock (or other ownership
               interest,  if not a  corporation)  of an entity or  management or
               operational control over such entity.

          (t)  "Costs"  means  actual,  direct  costs  incurred  and computed in
               accordance  with the  established  accounting  procedures used by
               Williams to bill third  parties for  reimbursable  projects.  All
               Costs shall be computed in  accordance  with  generally  accepted
               accounting  principles.  Such actual,  direct  costs  include the
               following:

               (i)  Labor costs,  including  wages and  salaries,  and benefits,
                    plus the overhead  allocable  to such labor costs  (overhead
                    allocation  percentage  shall not  exceed the lesser of: (i)
                    the percentage  Williams allocates to its internal projects;
                    or (ii) thirty percent  (30%));  and 

               (ii) Other   direct  costs  and   out-of-pocket   expenses  on  a
                    pass-through basis (such as equipment,  materials, supplies,
                    contract services, costs of capital, Required Rights, sales,
                    use or similar  taxes,  etc.) plus ten percent (10%) of such
                    expenses;  but, 

               (iii) Less any cost or expense reimbursed by a third party.

          (u)  "CPNIP"  has the  meaning  set  forth in Part I,  Section  2.1 of
               Schedule  B,  Williams  Network  Technical  Specifications.   

          (v)  "Deadline Date" has the meaning set forth in Section 4.2.

          (w)  "Deduction  Sections"  has  the  meaning  set  forth  in  Section
               24.1(l).

          (x)  "Dispute Notice" has the meaning set forth in Section 23.4(a).

          (y)  "Disputing Party" has the meaning set forth in Section 23.4.

          (z)  "Due Date" has the meaning set forth in Section 12.1.

          (aa) "Effective Date" means December 17, 1998.

          (bb) "Equipment"  has the meaning set forth in Section 1.1 of Schedule
               C, Part 2.

          (cc) "Exercise  Date" means the date on which  WinStar  exercises  its
               Option in accordance with Section 2.2.

          (dd) "Exercise Price" has the meaning set forth in Section 3.2.

          (ee) "Facility  Owners/Lenders" means any entity (other than Williams)
               that:  (a) owns any  portion  of the  System or any  property  or
               security interest therein, (b) leases to Williams, or provides an
               IRU to Williams in, any portion of the System, or (c) is a Lender
               with respect to Williams or any Affiliates of Williams.

          (ff) "FCC" means the Federal Communications Commission.

          (gg) "Fiber  Acceptance  Testing" means the fiber  acceptance  testing
               described in Exhibit D and in Article 7.

          (hh) "Fiber Collocation  Provisions" means the provisions set forth in
               Exhibit C, Part 1.
               

          (ii) "Fibers"  means  any  optical  fibers  contained  in  the  System
               including  the WinStar  Fibers,  the fibers of  Williams  and the
               fibers of any third party in the System excluding,  however,  any
               fibers  granted  (whether  through  ownership,   IRU,  lease,  or
               otherwise)  to  governmental  entities in exchange for the use of
               streets,  rights of way, or other property under the jurisdiction
               of such entity.

          (jj) "Force Majeure Events" has the meaning set forth in Article 22.

          (kk) "Indefeasible   Right  of  Use"  or  "IRU"  means  an  exclusive,
               indefeasible  right to use the specified  property or capacity in
               the manner  contemplated  by this Agreement;  provided,  however,
               that the grant of an IRU shall not convey  title,  ownership,  or
               rights of  possession  in the  System,  the WinStar  Fibers,  the
               Cable, the Right-of-Way Agreements, or any other real or personal
               property.

 
                                      3

<PAGE>

          (ll) "Indemnitor" has the meaning set forth in Section 15.1.

          (mm) "Initial  WinStar  Fibers"  has the  meaning set forth in Section
               2.1.

          (nn) "Intellectual   Property   Rights"   means   patent,   copyright,
               trademark,  trade secret or other proprietary rights with respect
               to any work product in which such rights could inure.

          (oo) "Interconnect/Collocation  Notice"  has the  meaning set forth in
               Exhibit C, Part 1, Section 3.

          (pp) "Interconnect  Facility"  has the meaning set forth in Exhibit C,
               Part 1, Section 2(a).

          (qq) "Interconnection"  has the meaning set forth in Section 6.2. 

          (rr) "Interim IRU" has the meaning set forth in Section 2.1(b).

          (ss) "IRU Term" has the meaning set forth in Section 9.2.

          (tt) "LEC" means a local exchange carrier.

          (uu) "Lender" has the meaning set forth in Section 2.3.

          (vv) "Losses"  means all  liabilities,  damages and related  costs and
               expenses (including fines, levies, assessments,  reasonable legal
               fees and disbursements  and costs of  investigation,  litigation,
               settlement,  judgment,  interest and penalties) directly incurred
               by a party.

          (ww) "Material  Improvements"  has the meaning set forth in Section 10
               of Exhibit C, Part 2.

          (xx) "Mean Time to Restore" has the meaning set forth in Exhibit B.

          (yy) "Minimum  Commitment"  means One Hundred Twenty  Million  Dollars
               ($120,000,000),   which  is  the   minimum   amount   of   On-Net
               Telecommunications  Services  in  United  States  dollars  to  be
               purchased  by WinStar  pursuant to the terms  hereof prior to the
               expiration of the fifth  anniversary of the Effective  Date. Such
               amount is included in the Contract Price.

          (zz) "Minimum  Term  Liability"  has the  meaning set forth in Section
               5.3(b).

          (aaa)"NCC" means Network  Control  Center,  as set forth in Exhibit I,
               Section  1(A).  

          (bbb) "Network IRU" has the meaning set forth in Section 2.1.

          (ccc)"Notice  of  Election"  has the  meaning  set  forth  in  Section
               15.2(a).

          (ddd)"OOS"  means  Out-of-Spec,  as set forth in  Exhibit  D,  Section
               1(B).

          (eee) "Off Net" means a Circuit that is not On Net.

                                       4
<PAGE>


          (fff)"On Net" means a Circuit  traversing the Williams Network between
               two Williams points of presence.

          (ggg) "Option Fibers" has the meaning set forth in Section 2.1.

          (hhh) "Option" has the meaning set forth in Section 2.2.

          (iii)"OTDR" means optical time domain  reflectometer,  as set forth in
               Exhibit D, Section 1(A).

          (jjj)"Other Services" means local access,  Interconnection,  Ancillary
               Services and Collocation Services.
               

          (kkk)"Payment  Deductions"  has  the  meaning  set  forth  in  Section
               24.1(l).

          (lll) "Payment Terms" has the meaning set forth in Section 3.1.

          (mmm)"Point of Presence" means a specified  location at which Williams
               originates or terminates services.

          (nnn) "Premises" has the meaning set forth in Exhibit C, Part 2.

          (ooo)"Prime  Rate"  means,  with  respect  of  any  period,  the  rate
               published  as Chase  Manhattan's  prime  rate in the Wall  Street
               Journal, or any successor  publication thereto, from time to time
               during such period.

          (ppp)"Pro-Rata  Share"  means a  proportion  equal to a fraction,  the
               numerator  of which  is the  number  of  WinStar  Fibers  and the
               denominator of which is all Fibers in the relevant System Segment
               Portion(s). If this fraction varies over different System Segment
               Portions,  then the Pro Rata Share shall be equal to the weighted
               average  (weighted by length as set forth in  Williams'  as-built
               drawings) of the relevant System Segment  Portions.  For example,
               if the  fraction  for 100  feet of the  relevant  System  Segment
               Portion is 0.1 and the fraction for the  remaining 50 feet of the
               relevant System Segment Portion is 0.07, the weighted average for
               the entire System Segment Portion would be 0.09.

          (qqq)"Released  Party"  means  each  of the  following  (but  excludes
               Williams and WinStar): 

               (i)  Any  Affiliates  or  Lenders  of the  other  party  and  any
                    Facility Owners/Lenders;

               (ii) Any  employee,  officer,  director,  stockholder,   partner,
                    member,  or trustee of the other party or of its Affiliates,
                    Lenders, or Facility Owners/Lenders; or

               (iii)Assignees   of  the   entities   included   in   the   above
                    subparagraphs   (a)  or  (b)  and  any  employee,   officer,
                    director,  stockholder,  partner, member, or trustee of such
                    assignees.

          (rrr)"Renegotiated  Backbone  Agreement"  means  an  Assumed  Backbone
               Agreement that Williams has  renegotiated as set forth in Section
               5.4(b).

                                       5
<PAGE>

          (sss) "Representatives" has the meaning set forth in Section 20.2.

          (ttt)"Requested  Start  Date" has the  meaning  set  forth in  Section
               5.2(b).

          (uuu) "Required Rights" has the meaning set forth in Section 4.1.

          (vvv) "Restricted Fiber" has the meaning set forth in Section 26.1.

          (www)"Right-of-Way     Agreements"     means     rights,     licenses,
               authorizations,  easements,  leases, fee interests, or agreements
               that provide for the  occupancy by the System of real property or
               fixtures  (such  as  conduit,   bridges,   river  crossings,   or
               transmission towers).

          (xxx) "Route" has the meaning set forth in the Recitals above.

          (yyy) "Routine Maintenance" has the meaning set forth in Section 10.1.
               

          (zzz)"Service  Orders" has the  meaning  set forth in Section  5.2(a).
               

          (aaaa)  "Service   Term"  means  with  respect  to  the  provision  of
               Telecommunications   Services,   Additional   Services  or  Other
               Services,  the length of time specified in the applicable Service
               Order during which Williams will provide such  Telecommunications
               Services, Additional Services or Other Services.

          (bbbb) "Space" has the meaning set forth in Section 1.1 of Schedule C,
               Part 2.
               

          (cccc) "Start  Date"  means,  with  respect to any  Telecommunications
               Services or Other Services WinStar  requests  Williams to provide
               hereunder, the first day on which such services are provided.
               

          (dddd) "Start of Service  Notice" or "SOSN" has the  meaning set forth
               in Section 5.2(e) .

          (eeee)  "System"  shall  have the  meaning  set forth in the  Recitals
               above.

          (ffff) "System  Segment"  means  one of the  System  Segment  Portions
               identified as a System Segment in Exhibit A, Part 2.

          (gggg) "System Segment Portion" means a discrete portion of the System
               and may refer to a span (a  portion  of the  System  between  two
               Transmission  Sites or between a Transmission Site and a point of
               presence  or System end point),  a portion  between two points of
               presence  or a point of  presence  and a System end  point,  or a
               portion  of  the  System   affected  by  a  relocation  or  other
               circumstance.

          (hhhh)     "Telecommunications     Services"    means    interexchange
               telecommunications   capacity  on  Williams'  Network  (or  third
               parties' telecommunications  facilities) at the DS-3, OC-3, OC-12
               and OC-48 levels but excluding Other Service.

          (iiii) "Term" has the meaning set forth in Section 9.1.

          (jjjj) "Third Party Service  Provider" means any third party provider,
               operator or maintenance repair contractor of facilities  employed
               by Williams in connection  with the provision of the Network IRU,
               Telecommunications Services or Other Services.

                                       6

<PAGE>

          (kkkk) "Transmission Sites" means the optical amplifier,  regenerator,
               and junction sites along each System Segment.

          (llll)  "Williams"  means  Williams  Communications,  Inc., a Delaware
               corporation, formerly known as Vyvx, Inc.

          (mmmm)  "Williams  Network"  means the  telecommunications  facilities
               owned  or  operated  by  Williams  and used to  provide  services
               between  the cities  listed on Exhibit O, as such may be added to
               as Williams grows its network during the Term.

          (nnnn) "WinStar"  has the meaning set forth in the first  paragraph of
               this document.

          (oooo)   "WinStar   Equipment"   means   optronic   (opto-electrical),
               electronic,  or optical equipment, or materials,  facilities,  or
               other  equipment  (other than the System)  owned,  possessed,  or
               utilized by WinStar.

          (pppp) "WinStar Facilities" has the meaning set forth in Section 26.3.

          (qqqq) "WinStar  Fibers"  means the Initial  WinStar  Fibers and, upon
               WinStar's  exercise of the Option in accordance with Section 2.2,
               the Option Fibers.

          (rrrr) "WinStar IRU" has the meaning set forth in Section 2.1. 

2.   CONVEYANCE OF DARK FIBER IRUS AND GRANT OF OPTION 

     2.1. Grant of Network IRU.

     Williams  hereby  grants  the  "Network  IRU" to WinStar  for the  purposes
     described  herein and on the terms and subject to the  conditions set forth
     herein. The Network IRU comprises:

     (a)  An exclusive  Indefeasible Right of Use (the "WinStar IRU"), effective
          as of the Acceptance  Date for each System  Segment,  in: 

          (i)  Four (4) strands of optical fiber (the "Initial WinStar Fibers"),
               as identified by Williams in each System Segment,  throughout the
               length of the Route;  and 

          (ii) If the  Exercise  Date  occurs,  two (2)  additional  strands  of
               optical fiber (the "Option Fibers"), as identified by Williams in
               each System Segment,  throughout the length of the Route; and 

     (b)  An exclusive  Indefeasible  Right of Use in On-Net  Telecommunications
          Services (the  "Interim  IRU"),  effective as of the  Effective  Date,
          which is further defined in Article 5. 

     2.2. Option.

     (a)  WinStar is hereby  granted an option (the  "Option")  to an  exclusive
          Indefeasible Right of Use in the Option Fibers in all System Segments.
          The Option is not divisible  (i.e. it may not be exercised in part) by
          System Segment or strand of Option Fiber. If not exercised, the Option
          shall expire on the seventh (7th)  anniversary of the Effective  Date.
     

     (b)  WinStar may  exercise  the Option  only by delivery of an  irrevocable
          written  notice to that  effect by an  authorized  representative.  If
          WinStar so exercises the Option:  

          (i)  The Option Fibers will be deemed to be WinStar Fibers (except for
               purposes of Article 7, for which separate  treatment is indicated
               in Section  7.8) and will be deemed to be subject to the  WinStar
               IRU;  and 

          (ii) WinStar's  rights to use the Option  Fibers  shall begin upon the
               initial  payment  of  the  Exercise  Price  (or,  if  later,  the
               Acceptance Date for each System Segment) and shall continue until
               the last day of the IRU Term of the corresponding System Segment.


     2.3. Financing Arrangements.

     Each party may,  directly  or through an  Affiliate,  enter into  financing
     arrangements  (including  secured  loans,  leases,  sales with  lease-back,
     leases with lease-back  arrangements,  purchase-money  or vendor financing,
     conditional  sales  transactions  or other  arrangements)  with one or more
     financial institutions, vendors, suppliers or other financing sources (each
     a "Lender"), that, with respect to Williams, relate to the System and, with
     respect to  WinStar,  relate to the  Network  IRU (and not to any  physical
     property right in the System),  subject to Williams' rights pursuant to the
     Payment Terms. 

     2.4. Preferred Provider Status.

     (a)  During the Term,  WinStar  shall  first  seek to obtain  its  domestic
          interexchange  telecommunications  requirements (including dark fiber,
          data,  voice and video  circuits) from Williams.  WinStar will fulfill
          such  requirements  with  Williams'   telecommunications  products  if
          Williams is responsive to WinStar's requests and those products,  when
          compared to similar offerings in the marketplace, are of equivalent or
          better quality,  availability and price. 

     (b)  Within 180 days after the  Effective  Date,  the parties  will jointly
          establish a  benchmarking  measurement  and  comparison  process  (the
          "Benchmarking  Process") designed to objectively  evaluate whether the
          Williams  Telecommunications  Services,  Additional  Services or Other
          Services,  as  applicable,   are  of  equivalent  or  better  quality,
          availability  and price as  compared  to  similar  services  generally
          available  in the  market  for  similar  size and  scope  requirements
          ("Market  Level  Charges").  The  Benchmarking  Process will take into
          consideration  relevant  factors such as quality and  delivery  terms.

     2.5. Most Favored Customer Provision.

     During the Term,  if Williams  sells  On-Net  Telecommunications  Services,
     On-Net  Additional  Services,  and/or Other Services (but not including any
     local  access or dark/dim  fiber) to a third party on  Financial  Terms (as
     hereinafter  defined) that are not Comparable (as  hereinafter  defined) to
     those provided hereunder, WinStar shall be entitled to an adjustment of the
     amounts paid with regard to the On-Net Telecommunications  Services, On-Net
     Additional  Services,  and/or Other  Services in question.  Williams  shall
     promptly notify WinStar in writing of such more favorable  Financial Terms.
     Williams  shall be under no  obligation to disclose to WinStar the identity
     of any such third party or any other provisions of such a contract that are
     not more favorable than those provided to WinStar. Such adjustment shall be
     equal  to the  aggregate  amount  necessary  to make  the  Financial  Terms
     Comparable  (pro rated to follow the cash timing of this  Agreement).  Upon
     payment or credit of such  adjustment to WinStar,  the  Financial  Terms of
     this Agreement  shall be deemed to be those more favorable  Financial Terms
     for the purpose of future  applications  of this  Section.  Nothing in this
     Section  shall be deemed to require  Williams to sell more than the Minimum
     Commitment  contained herein.  "Comparable"  means not less than the price,
     after  adjustments  to take into account all  differences  attributable  to
     volume,  terms and  conditions,  advances in  technology,  passage of time,
     market conditions or strategic relationship value.  "Financial Terms" means
     the overall pricing of services to the third-party.

     2.6      No Title to Realty or Personalty.

     Neither this  Agreement  nor the grant of the Network IRU  effected  hereby
     conveys  any  form or type  of  title  in any  real or  personal  property,
     including the System or any portion thereof or in any transmission or other
     facilities  and equipment  related to the  provision of  Telecommunications
     Services,  Other  Services,  or Additional  Services.  Williams and WinStar
     intend that this  Agreement  constitutes a true lease of the WinStar Fibers
     and not a sale of the WinStar Fibers.  Notwithstanding  such express intent
     of the parties, if a court of competent  jurisdiction  determines that this
     Agreement  is not a true  lease,  but a security  interest  in the  WinStar
     Fibers,  then  solely in that  event and  solely  for the  limited  purpose
     thereof,  WinStar  shall be  deemed to have  granted  Williams  a  security
     interest  as  described  in  Section 7 of Exhibit K hereto.  WinStar  shall
     provide an inventory of any equipment to be located on Williams'  sites. 

                                       9
<PAGE>

3.   CONSIDERATION FOR IRUS 

     3.1. Contract Price.

     As  consideration  for the Network IRU,  WinStar  shall pay  Williams  Five
     Hundred and Fifty Million Dollars  ($550,000,000) (the "Contract Price") in
     accordance  with the  payment and other terms set forth in Exhibit K hereto
     (the "Payment Terms"),  plus the Exercise Price if the Option is exercised.
     
     3.2. Exercise Price.

     The price payable if WinStar  exercises the Option (the  "Exercise  Price")
     shall be Fifty-One Million Eight Hundred  Thirty-Four  Thousand One Hundred
     Dollars  ($51,834,100),  allocated  to each System  Segment as set forth in
     Exhibit A, Part 2. The  Exercise  Price for each  System  Segment  shall be
     chargeable  upon the later of (a) the date WinStar  exercises the Option or
     (b) the  Acceptance  Date of that  System  Segment.  

4.  CONSTRUCTION  

     4.1. Construction Representations, Warranties and Covenants.

     (a)  Williams represents, warrants and covenants that, as of the Acceptance
          Date for each System Segment,  it (or the underlying facility owner on
          Williams'   behalf)   shall  have   obtained  the   following   rights
          (collectively, the "Required Rights"): 

          (i)  All  Right-of-Way  Agreements  necessary for the installation and
               use of that System  Segment;  

          (ii) The rights to use those System  Segment  Portions it does not own
               and the  right to grant  the  Network  IRU with  respect  to such
               System Segment Portions;  

     (b)  Williams  represents,  warrants and  covenants  that,  for each System
          Segment,  

          (i)  That System Segment has been designed, engineered, installed, and
               constructed in accordance  with the  specifications  set forth in
               Exhibits  D, E, F and G; and 

          (ii) Throughout the relevant IRU Term, the exercise of rights by or on
               behalf of Williams'  Facilities  Owners/Lenders shall not deprive
               WinStar of the peaceful and quiet enjoyment of the WinStar IRU in
               that System Segment. 

     4.2. Delivery of System Segments.

     (a)  Deadline  Date.  The planned  Acceptance  Date for each System Segment
          shall be the date sixty (60) days after the Planned  Construction Date
          set forth as such in Exhibit A, Part 2. The  "Deadline  Date" shall be
          sixty (60) days after the later of (a) such planned Acceptance Date or
          (b) the planned  Acceptance  Date as extended due to unforseen  events
          not in the  reasonable  control  of  Williams  (other  than  as due to
          Williams' negligence),  Force Majeure Events or as expressly permitted
          by this  Agreement.  Williams  shall  implement each System Segment so
          that it achieves its Acceptance  Date by the Deadline  Date.  Williams
          shall give WinStar as much prior notice as reasonably possible if , to
          the best of Williams'  knowledge,  there is a forseeable  risk that it
          may miss a Deadline Date for any System  Segment.  

                                       10
<PAGE>

     (b)  Failure to Meet Deadline  Date. If Williams does not meet the Deadline
          Date for any System  Segment,  and the  parties  are  unable,  in good
          faith,  to agree to an alternative  Deadline Date,  WinStar's sole and
          exclusive  monetary  remedy for such failure  shall be to obtain Cover
          (as hereinafter defined) beginning on the Deadline Date for the System
          Segments  not made  available.  Such  "Cover"  shall be  satisfied  by
          Williams'  providing,  at Williams'  expense:  (a) such capacity as is
          required for WinStar to carry those Circuits it would have migrated to
          the  WinStar  Fibers,  and (b) such  other  capacity  as is  needed to
          fulfill  WinStar's  increase in usage  (based on actual  orders of its
          customers),  until Williams delivers the WinStar Fibers. In any event,
          Williams  will provide such Cover  capacity in ATM,  private  line, or
          frame relay formats,  at WinStar's  option.  

     4.3.  Renewal of Required Rights.

          Williams  shall  renew or replace  existing  Required  Rights for each
          System Segment through at least the applicable IRU Term. 

     4.4. As-Built Drawings.

          Within  six (6)  months  after  the  Acceptance  Date  for any  System
          Segment,  Williams  shall provide  WinStar with as-built  drawings for
          that  System  Segment,  in  compliance  with  the  specifications  for
          as-built drawings set forth in Exhibit H. 

     4.5. Third-Party Consents.

          WinStar  acknowledges  that  Williams  requires the consent of a third
          party  in  order  to  grant   WinStar  an  IRU  with  respect  to  the
          Washington-Houston  and Houston-Dallas System Segments.  WinStar shall
          not  unreasonably  withhold  consent  to  changes  to  this  Agreement
          required by such third party that do not  adversely  affect  WinStar's
          rights and obligations under this Agreement and do not require payment
          of additional  consideration  by WinStar.  If WinStar consents to such
          changes,  the  parties  shall  execute an  appropriate  amendment.  If
          WinStar does not consent to such  changes,  or the  Required  Consents
          cannot be obtained  for other  reasons,  then the  Contract  Price and
          Exercise  Price  shall  each be reduced  by the  corresponding  amount
          allocated to the affected  System  Segment(s) in Exhibit A, Part 2. 

                                       11
<PAGE>

5.   ORDERING AND PROVISIONING 

     5.1. Provision of Interim Service.

     (a)  Inasmuch as the deployment of the System does not currently  reach all
          locations  set forth in Part 1 of Exhibit A, Williams  shall  provide,
          subject   to   availability   and  on  a   non-discriminatory   basis,
          Telecommunications Services on the Williams Network in accordance with
          the terms of this Agreement.  Such Telecommunications  Services may be
          part of the Minimum Commitment or may be Additional  Services.  

     (b)  At the request of Williams,  WinStar  shall pay for Other  Services or
          Additional  Services requested by WinStar in accordance with the terms
          of this Agreement. 

     (c)  Within ninety (90) days after each of the first five (5) anniversaries
          of the Effective Date,  Williams shall determine  WinStar's actual use
          of Minimum  Commitment  for the year  ending on such  anniversary  and
          shall send such information to WinStar for review. Irrespective of any
          shortfall in Minimum  Commitment  actually used by WinStar  during any
          period,  in no event  shall any  refund,  rebate or  reduction  in the
          Contract  Price be  granted or paid to WinStar as a result of any such
          shortfall.  Williams  shall be  obligated  to  accept  any  conforming
          Service  Orders  issued  by  WinStar  for  On-Net   Telecommunications
          Services  up  to  the  Minimum   Commitment   during  the  first  five
          anniversaries of the Effective Date.  Williams shall permit WinStar to
          take up to two (2)  months  beyond  the fifth  anniversary  beyond the
          Effective Date to use  Telecommunications  Services requested and paid
          for  under a  Service  Order for  On-Net  Telecommunications  Services
          issued prior to the end of the fifth anniversary of the Effective Date
          to enable WinStar to meet the Minimum Commitment.  Notwithstanding the
          foregoing,  WinStar  shall have  additional  time beyond the foregoing
          five  year  period  to  meet  the  Minimum  Commitment  to the  extent
          WinStar's  failure to meet the Minimum  Commitment is due to delays by
          Williams' in providing any of the On-Net  Telecommunications  Services
          by the firm order  commitment date issued by Williams during such five
          year period. 

     5.2. Service Orders for Interim Services.

     (a)  Telecommunications  Services,  Additional Services, and Other Services
          requested by WinStar  hereunder shall be requested on Williams Service
          Order  forms in effect  from  time to time  ("Service  Orders").  Each
          Service Order shall  reference this Agreement.  Williams  reserves the
          right not to accept a Service  Order  that does not  conform  with the
          terms and conditions of this Agreement and such non-conforming Service
          Order shall have no force or effect hereunder.  

                                       12

<PAGE>

     (b)  Each Service Order will indicate a requested due date (the  "Requested
          Start  Date")  for the  Circuit,  the  desired  term  of the  Circuit,
          specific city pairs, applicable bandwidth,  whether the Circuit(s) are
          to be  expedited  or  provided  in  normal  intervals  and  any  other
          parameters required. Williams shall acknowledge receipt of the Service
          Order,    on   average,    within    forty-eight    (48)   hours   (an
          "Acknowledgement").   Within   four   (4)   business   days   of   the
          Acknowledgement,   Williams   will   advise   WinStar  as  to  network
          availability.  With respect to On-Net Circuits,  when WinStar requests
          to order its own local loops  Williams will provide a Letter of Agency
          within  seven to ten  business  days  after  Williams'  receipt of the
          Service Order.  Within  twenty-four (24) hours after Williams' receipt
          of the Design  Layout  Record (as  provided  by the  applicable  local
          access  provider),  Williams will provide a firm order  commitment for
          On-Net  Circuits.  All Service Order intervals for Off-net Circuits or
          Backbone Agreement Circuits are on an individual case basis.  Williams
          will use reasonable efforts to assist WinStar in obtaining a Letter of
          Agency and delivering service from a Third-Party Provider.  All On-Net
          DS-3/OC-3 Circuits ordered by WinStar pursuant to Service Orders under
          this  Agreement  will be  provisioned  by  Williams  within  a  target
          timeframe of  forty-five  (45) days from the date of the Service Order
          for POP to POP service.  

     (c)  Once a Service  Order is placed,  WinStar may cancel it only by notice
          of  cancellation  not  less  then ten days  prior to  delivery  of the
          corresponding  Circuit, and payment of any specified cancellation fee.
          WinStar   agrees  that  the  actual  damages  in  the  event  of  such
          cancellation  would be difficult or impossible to ascertain,  and that
          the cancellation  charge set forth in herein is consequently  intended
          to  establish   liquidated   damages  and  not  a  penalty.   

     (d)  Any   conflicting,   different  or  additional  terms  and  conditions
          contained in WinStar's  acknowledgment  or Service  Order or elsewhere
          are deemed  objected to by Williams and shall not  constitute  part of
          this Agreement.  No action by Williams (including  fulfillment of such
          Service  Order) shall be  construed  as binding or estopping  Williams
          with  respect to such  conflicting,  different or  additional  term or
          condition,  unless the Service Order containing said term or condition
          has been  signed by an  authorized  representative  of  Williams.  

     (e)  Williams shall make reasonable  efforts to provide  Telecommunications
          Services,  Other Services and Additional  Services within its standard
          service  implementation  interval, as set forth herein or on WinStar's
          Requested Start Date.  Telecommunications  Services, Other Services or
          Additional Services,  as applicable,  shall begin on the date Williams
          issues a notice  that  service  is  available  (the  "Start of Service
          Notice" or "SOSN"), indicating the service has been tested by Williams
          in accordance  with  Williams'  standard  specifications  and that the
          service  meets  or  exceeds  those  specifications.  

                                       13

<PAGE>

     (f)  WinStar may  reasonably  request  one or more delays in the  Requested
          Start Date of a Service  Order, a move, or  rearrangement  if Williams
          receives  the delay  request at least  fifteen  (15) days prior to the
          Requested  Start  Date and the  requested  delay  does not  extend the
          Requested Start Date more than thirty (30) days from the original date
          thereof.  If WinStar delays the Requested  Start Date (or as gauged by
          the SOSN, if issued for a date after the Requested Start Date) by more
          than  thirty  (30)  days,  WinStar  has the  option to (a)  accept the
          billing   for  the   Service   Order,   (b)  in  the  case  of  On-Net
          Telecommunications  Services,  Other Services, or Additional Services,
          cancel the Service Order and pay the applicable  cancellation  charges
          for  the   facilities   ordered,   or  (c)  in  the  case  of  Off-Net
          Telecommunications  Services,  Other Services, or Additional Services,
          cancel the Service  Order and pay any charges or other costs  Williams
          incurs as a result of such  cancellation.  The billing or cancellation
          will be effective  thirty (30) days after the Requested Start Date. If
          WinStar elects to accept billing,  the installation  will be completed
          as soon as reasonably  practical after WinStar  advises  Williams that
          the installation can be completed. 

     (g)  Subject to the terms of Section 24.1(l),  if, after the relevant Start
          Date, Williams is in material breach of its obligation to issue a SOSN
          for On-Net  Telecommunications  Services (excluding any breach arising
          from delays in  obtaining  or  failures to obtain or maintain  service
          such as local  access or Off-Net  service,  but  excluding  POP-to-POP
          On-Net  service)  for a period of more than one hundred  twenty  (120)
          consecutive days after WinStar provides written notice of such breach,
          WinStar may deduct from each succeeding  monthly  invoice,  so long as
          that  breach  continues,  the amount by which such  Telecommunications
          Services  would   otherwise  have   contributed   toward  the  Minimum
          Commitment  during any month  following  such one hundred twenty (120)
          day period.  Upon  Williams'  issuance of the  corresponding  SOSN, no
          further   deductions   shall  be   available   to  WinStar   for  such
          Telecommunications Services. 

     5.3. Changes in Service Parameters.

     (a)  WinStar  may  disconnect  Off-Net  Telecommunications  Service,  Other
          Services,  or Additional  Services  provided by a Third-Party  Service
          Provider  pursuant to a Service  Order by  providing  sixty (60) days'
          prior written notice and paying any and all amounts  properly due that
          Provider for the affected  Service  Order.  

     (b)  Following the relevant Start Date for any On-Net service,  WinStar may
          disconnect  or  reconfigure  that  service upon sixty (60) days' prior
          written notice.  If that action relates to a Circuit that has not been
          in place for at least one (1) year from its Start  Date,  (i)  WinStar
          shall pay Williams an amount equal to the total of the monthly charges
          for one year of  service of such  Circuit,  less the amount of monthly
          charges  actually  paid at the  time  of  service  disconnection  (the
          "Minimum Term  Liability")  and (ii),  WinStar shall also pay Williams
          the additional charges set forth in this Agreement that are associated
          with that disconnection or reconfiguration. Subsection (ii) shall also
          apply in the  event  of a  cancellation  in  accordance  with  Section
          5.2(c).

                                       14

<PAGE>

     5.4. Assignment and Assumption of Backbone Agreements.

     (a)  Assumption.  Subject to subsection (i) below and WinStar obtaining any
          necessary required consents,  WinStar will assign to Williams pursuant
          to a mutually  acceptable  assignment  and assumption  agreement,  all
          Backbone Agreements that can be assigned,  to the extent that Williams
          has the requisite intrastate or international authority to provide the
          services  encompassed  by such  Backbone  Agreements.  The date of the
          assignment shall be the "Assignment  Agreement  Effective Date". After
          such  assumption,  the terms and  conditions of such Assumed  Backbone
          Agreements or such  Renegotiated  Backbone  Agreement,  as applicable,
          (including all technical standards and service provisioning intervals)
          shall prevail  solely with regard to services  provided by Williams to
          WinStar  thereunder,  except as to any Circuit which has been migrated
          on Williams  Network as provided below.  

     (b)  Renegotiation.   Williams  shall   renegotiate  the  Assumed  Backbone
          Agreements,  as it is  reasonably  able,  to  improve on the terms and
          pricing thereof.  Any such renegotiated terms shall only be applicable
          to  WinStar  to the extent it  improves  the terms and  pricing of the
          Backbone  Agreement as assigned to Williams.  Once an Assumed Backbone
          Agreement  is  renegotiated,  it shall be  considered  a  Renegotiated
          Backbone  Agreement for all purposes  herein.  Williams will only pass
          through to WinStar,  and WinStar  shall be entitled  to, its  pro-rata
          share of such  cost  savings  achieved  in any  Renegotiated  Backbone
          Agreement. WinStar's pro-rata share will be determined by dividing the
          then  current  WinStar  Circuit  or  billing  volumes by the total new
          Circuit or billing volume under the Renegotiated  Backbone  Agreement.
         

     (c)  Payment Agent.  WinStar shall designate  Williams as its payment agent
          with  respect to all  Backbone  Agreements  that cannot be assigned to
          Williams pursuant to subsection (a) above.

     (d)  Payment  and  Minimum  Commitments.  WinStar  shall pay  Williams  for
          services   rendered   under  the  Assumed   Backbone   Agreements  and
          Renegotiated  Backbone  Agreements at the rates therein and shall also
          remain  responsible  for meeting  the  associated  minimum  revenue or
          volume  commitments,  if any (the  "Minimums").  With  respect  to any
          Renegotiated   Backbone   Agreement,   WinStar   shall  abide  by  the
          renegotiated terms and conditions,  including paying the reduced price
          as set forth in subsection (b) above.  WinStar shall, in all instances
          and  to  the  extent  such   amounts  are   pre-calculated,   pay  the
          non-recurring and monthly recurring charges to Williams in immediately
          available  funds at least  one  billing  cycle  prior to the date that
          payment  is due  from  Williams  to  the  Backbone  Agreement  Service
          Provider  under  an  Assumed  Backbone  Agreement  or  a  Renegotiated
          Backbone Agreement. 


                                       15
<PAGE>

     (e)  Administration.  The  parties  will  work  together  to  identify  the
          Circuits  related to each Backbone  Agreement and,  after  assignment,
          minimum revenue or volume commitments of WinStar,  if any,  associated
          with  the  Assumed  Backbone  Agreements  and  Renegotiated   Backbone
          Agreements.  In no event shall WinStar be responsible  for any minimum
          revenue or volume commitments under a Renegotiated  Backbone Agreement
          beyond such commitments agreed to by WinStar prior the Effective Date.
          Subject to WinStar's confidentiality obligations, WinStar will provide
          Williams  reasonable access to its records,  books and other documents
          and  data  related  to  each  Backbone  Agreement,   Assumed  Backbone
          Agreement  and  Renegotiated  Backbone  Agreement.  WinStar  will also
          cooperate  with  Williams in the  administration  of such  agreements.
          Williams is not  obligated to assume any Circuit until such Circuit is
          identified  by  the  parties.  

     (f)  WinStar  Disputes.  Williams  will  endeavor to resolve,  on behalf of
          WinStar and at  WinStar's  expense,  any  back-billing  dispute  which
          accrued prior to the applicable  Assignment  Agreement  Effective Date
          (provided  that  notice of any such  dispute is  received  by Williams
          before any such Assignment  Agreement Effective Date) and WinStar will
          cooperate  fully in any such  effort.  

     (g)  Orders Under  Assumed and  Renegotiated  Backbone  Agreements.  Unless
          otherwise  permitted  by  Williams,  WinStar  will place  orders under
          Assumed  Backbone  Agreements  and  Renegotiated  Backbone  Agreements
          through Williams. Williams will not be obligated to accept any Circuit
          arranged  by  WinStar  in  contravention  of this  provision  and such
          Circuit  will not become  subject  to the  Assignment  and  Assumption
          Agreement unless  otherwise agreed to by Williams,  such agreement not
          to be unreasonably withheld.
          

     (h)  Relationship  to the Minimum  Commitment and  Migration.  Provision of
          service under any Backbone  Agreement  (including the Assumed Backbone
          Agreements and Renegotiated Backbone Agreements) will not count toward
          satisfaction  of the  Minimum  Commitment  until  such  time  as  such
          Circuits are migrated onto the Williams Network.  Subject to WinStar's
          prior  approval in each  instance,  Williams  shall  migrate  Circuits
          provided  under  any  Assumed  Backbone   Agreements  or  Renegotiated
          Backbone  Agreements  as  soon as  reasonably  possible,  taking  into
          account any Circuit terms,  early  termination  fees or Minimums.  

     (i)  Assumption  Proviso.  Williams  shall not be  obligated  to assume any
          Backbone  Agreement  that  would  materially   conflict  with  another
          Williams contract,  have a materially  adverse effect on Williams,  or
          that contains any material usage commitment based upon a percentage of
          WinStar's  telecommunications  needs.  In the event  Williams does not
          assume such Backbone  Agreement,  Williams will act as a payment agent
          as  provided  in  Section  5.4(c).  

                                       16

<PAGE>

6.  CONNECTION  TO THE  SYSTEM AND COLLOCATION 

     6.1. Collocation.

     (a)  WinStar shall have the right to use Transmission Sites along the Route
          pursuant to the Fiber Collocation Provisions.  Such Transmission Sites
          shall meet or exceed the power and building requirements  specified in
          Exhibit G. WinStar shall  provide,  maintain,  and for all purposes be
          solely  responsible for all WinStar Equipment at Transmission Sites or
          other locations.


     (b)  Collocations  in  Williams  Points of  Presence  will be  provided  in
          accordance with the terms contained in Exhibit C, Part 2.

     (c)  Subject to the terms of Section 24.1(l), if, after the Acceptance Date
          for  any  System  Segment,  Williams  is in  material  breach  of  its
          obligation  to provide the rack space or square  footage  specified by
          the  Collocation   Provisions  at  any  Transmission  Site  (excluding
          Transmission Sites on the Dallas-Houston  System Segment) for a period
          of more than one hundred twenty (120)  consecutive  days after WinStar
          provides  written  notice  of such  breach,  WinStar  may  deduct  the
          following  amount  from its  monthly  invoice,  pro-rated  for partial
          months,  so long as that  material  breach  continues  beyond such one
          hundred twenty (120) day period:  (i) Five Thousand  Dollars  ($5,000)
          per month prior to the eighth  anniversary of the relevant  Acceptance
          Date, (ii) one thousand dollars ($1,000) per month from the the eighth
          anniversary  of the relevant  Acceptance  Date up to but not including
          the tenth anniversary of the relevant  Acceptance Date, and (iii) five
          hundred dollars ($500) per month thereafter.  The preceding  provision
          shall  apply  on a  per-Transmission  Site  basis  for  each  relevant
          Transmission Site. 

     6.2. Interconnection.

     (a)  With respect to each of the cities served by the WinStar  Fibers,  the
          parties  shall  mutually   determine  the  most  efficient  manner  of
          providing the required  connectivity  ("Interconnection")  between the
          WinStar and Williams points of presence, whether through then-existing
          installed  capacity,  implementation  of new  capacity  or third party
          arrangements.  In  addition,  the parties  shall set and  periodically
          review the schedule (timing and priority) of  implementation  of those
          Interconnection  facilities  and  shall  adhere  to that  schedule  in
          implementing such facilities.

                                       17
<PAGE>


     (b)  The parties shall allocate the costs of each Interconnection  facility
          as follows:

          (i)  The parties shall  mutually agree upon a forecast of each party's
               usage of that  Interconnection  facility  during  the first  year
               after  implementation  (the "Forecast").  The non-recurring costs
               associated  with  the  implementation  of that  facility  and the
               recurring  cost  thereof  in the  first  month of  operation  (in
               aggregate,  the  "Start-up  Costs")  will be  allocated  pro rata
               between the parties based upon the Forecast.  One year thereafter
               the parties  shall  re-calculate  the  allocation of the Start-up
               Costs by  substituting  actual usage during the preceding year in
               place of the Forecast.  Based upon that  recalculation,  Williams
               shall  pay or  receive  a refund,  in  either  case  equal to the
               difference  between the initial  allocation of the Start-up Costs
               and the recalculated  amount, plus interest at the Prime Rate for
               the applicable period.

          (ii) On a quarterly  basis,  the parties  shall  allocate the periodic
               recurring costs of that Interconnection facility pro rata between
               the parties based upon actual usage during the preceding quarter.

          (iii)Following the Effective  Date, the parties will mutually  develop
               appropriate procedures to implement the foregoing. 

     6.3. Ancillary Services.

          Williams  may also  provide  other  services  to WinStar  for  reasons
          including,  but not  limited  to: (a)  WinStar's  request to  expedite
          Telecommunications  Services  availability  to  a  date  earlier  than
          Williams'  published  installation  interval or a previously  accepted
          Start Date; (b) Telecommunications Services redesign or other activity
          occasioned by receipt of  inaccurate  information  from  WinStar;  (c)
          WinStar's  request  for use of routes or  facilities  other than those
          selected by Williams for provision of the Telecommunications Services;
          and (d) other  circumstances in which extraordinary costs and expenses
          are  generated  at the  written  request of WinStar  and  incurred  by
          Williams  (collectively,  "Ancillary  Services").  

7.  ACCEPTANCE  AND TESTING OF FIBERS 

     7.1. Overview.

          Fiber Acceptance  Testing of the WinStar Fibers shall be conducted for
          each System Segment Portion  ("System Segment Portion Fiber Acceptance
          Testing" or  "SSPFAT").  The  provisions  set forth below  address the
          acceptance   procedures  and  provisions  regarding  failure  notices,
          corrections,  third party  testing  and testing of the Option  Fibers.



                                       18

<PAGE>

     7.2. SSPFAT by Williams.

          Williams shall perform SSPFAT of the WinStar Fibers in accordance with
          Exhibit D. SSPFAT  shall  progress  System  Segment  Portion by System
          Segment  Portion  along  the  Route of each  System  Segment  as cable
          splicing progresses,  so that test results may be reviewed in a timely
          manner. WinStar shall have the right, but not the obligation,  to have
          an individual  present to observe  Williams'  SSPFAT or to conduct its
          own SSPFAT in  accordance  with Section 7.3 below  (except,  in either
          case, to the extent  Williams' System Segment Portion Fiber Acceptance
          Testing  takes place prior to the period ending twenty (20) days after
          the Effective Date).  Williams shall provide WinStar at least ten (10)
          days prior notice of Williams' testing schedule or any change thereto.
          Within  twenty  (20) days  after the  conclusion  of any SSPFAT of the
          WinStar  Fibers  conducted  by  Williams in any given  System  Segment
          Portion,  Williams  shall  provide  WinStar  with a copy  of the  test
          results  provided  that in no case  shall  Williams  be  obligated  to
          provide  copies of such test results  before  January 11,  1999.  

     7.3. SSPFAT by WinStar.

          WinStar  shall have the  right,  but not the  obligation,  at its sole
          expense,  to conduct  its own SSPFAT of the  WinStar  Fibers to verify
          that they meet the Acceptance Standards.  If WinStar elects to conduct
          its own SSPFAT of the WinStar Fibers,  it shall notify Williams of its
          intent to do so  (including  dates and  locations)  at least three (3)
          days  prior to the date of  Williams'  scheduled  commencement  of the
          SSPFAT  of  a  particular  System  Segment  Portion  as  specified  in
          Williams'  ten day prior  written  notice to  WinStar as  provided  in
          Section  7.2.  WinStar  may elect to perform  such  testing (i) itself
          subsequent to the Williams testing or (ii) concurrently with Williams'
          testing  (except to the extent  Williams'  testing take place prior to
          the period ending twenty (20) days after the Effective Date), in which
          case  both  parties  shall  reasonably  cooperate  with  the  other to
          facilitate such concurrent  testing.  If WinStar elects to perform the
          testing itself subsequent to Williams' testing,  WinStar will complete
          such testing within ten (10) days after Williams  completes its SSPFAT
          of the  relevant  System  Segment  Portion  (except to the extent such
          Williams  testing  takes place prior to the period  ending twenty (20)
          days after the  Effective  Date in which case WinStar  shall  complete
          such SSPFAT by January 25, 1999).  Williams shall have the right,  but
          not the obligation, to have an individual present to observe WinStar's
          SSPFAT.  Within  twenty (20) days after the  conclusion  of  WinStar's
          SSPFAT of the WinStar  Fibers,  WinStar shall provide  Williams with a
          copy of the test results.  WinStar's  exercise or  non-exercise of its
          right to conduct  SSPFAT  shall not extend or shorten the time periods
          for  WinStar to  determine,  pursuant  to Section  7.4,  if the System
          Segment  Portion  meets  the  Acceptance  Standards.   Williams  shall
          reasonably  cooperate  with WinStar to facilitate  SSPFAT.  Changes in
          testing  schedules  may be mutually  agreed upon by the Parties.  

                                       19
<PAGE>

     7.4. Failure Notice.

          If,  within  fourteen  (14) days  after the  later of (i)  receipt  by
          WinStar from  Williams of the test results  referred to in Section 7.2
          or of the results of  re-testing  as set forth below and (ii)  WinStar
          conclusion  of its own  testing as provided  in Section  7.3,  WinStar
          reasonably  determines  that  Williams' or WinStar's test results show
          that the System Segment  Portion of the WinStar Fibers do not meet the
          Acceptance  Standards,  WinStar  shall,  within such fourteen (14) day
          period,  notify Williams of such  determination  and shall identify in
          writing  the  specific  data that  indicate  such  failure to meet the
          Acceptance Standards.  Notwithstanding the foregoing,  if the fourteen
          (14) day period ends prior to January 25, 1999 for any System  Segment
          Portion,  WinStar  will have until  January 25, 1999 to give  Williams
          notice  of  failures  of  the  System  Segment  Portion  to  meet  the
          Acceptance Standard. 

     7.5. Correction.

     (a)  Upon  receiving  notice  pursuant to Section 7.4 that a System Segment
          Portion of the WinStar  Fibers do not meet the  Acceptance  Standards,
          Williams  shall  either:   

          (i)  Expeditiously  take such action as reasonably  necessary to cause
               such System Segment Portion to meet the Acceptance  Standards and
               then re-test in accordance  with the  provisions of this Article;
               or  

          (ii) Notify  WinStar that Williams  disputes  WinStar's  determination
               that the System Segment Portion of the WinStar Fibers do not meet
               the Acceptance Standards. 

     (b)  After taking corrective  actions and re-testing the WinStar Fibers (if
          appropriate),  Williams  shall provide  WinStar with a copy of the new
          test results and WinStar shall again have all rights  provided in this
          Article with  respect to such new test  results.  The cycle  described
          above of testing,  taking  corrective action and re-testing shall take
          place  until  the  WinStar  Fibers  meet  the  Acceptance   Standards;
          provided,  however,  repeating  this  cycle  shall  not in any  manner
          whatsoever limit any other right or remedy WinStar may have under this
          Agreement. 

     7.6. Testing by Third Party.

          If  Williams   provides  notice  to  WinStar  pursuant  to  Subsection
          7.5(a)(ii),  and the parties are unable to otherwise  mutually  agree,
          the parties  shall appoint a mutually  acceptable  fiber optic testing
          company and such company shall re-test the  applicable  System Segment
          Portion of the  WinStar  Fibers.  If that test  demonstrates  that the
          tested  System  Segment   Portion  of  the  WinStar  Fibers  meet  the
          Acceptance  Standards  without any changes to such portion by Williams
          as tested by WinStar,  then  WinStar  shall pay the testing  company's
          charges  and shall be  deemed to have  accepted  the  relevant  System
          Segment Portion of the WinStar Fibers.  If that test demonstrates that
          the relevant  System Segment Portion of the WinStar Fibers do not meet
          the Acceptance Standards or that they do meet the Acceptance Standards
          due  to  changes  made  by  Williams  following  WinStar's  acceptance
          testing,  then Williams  shall pay the testing  company's  charges for
          performing  the testing and shall  perform the  corrective  action and
          re-testing  set forth in Subsection  7.5(a)(i).  

                                       20
<PAGE>

     7.7.  System  Segment Fiber Acceptance Testing and Acceptance Date.

          If the Fiber  Acceptance  Testing for all System Segment Portions of a
          System  Segment  shows that the  WinStar  Fibers  meet the  Acceptance
          Standards  and WinStar does not object to the results of any SSPFAT by
          written  notice  within the time  periods  specified  in Section  7.4,
          WinStar  shall  be  deemed  to have  accepted  the  particular  System
          Segment.  The date of WinStar's notice accepting the System Segment of
          the WinStar Fibers or the date of deemed acceptance under this Article
          for the  last  of all of the  System  Segment  Portions  for a  System
          Segment to be accepted shall be the  "Acceptance  Date" of the WinStar
          Fibers for that System  Segment.  The provisions of this Section shall
          not be deemed to relieve Williams of its obligation to provide Routine
          Maintenance or non-Routine Maintenance as set forth in this Agreement.

     7.8. Testing of Option Fibers.

          Williams  shall include the Option Fibers in the SSPFAT of each System
          Segment. Upon WinStar's exercise of the Option, Williams shall provide
          copies  of  the  results  of all  SSPFAT  of the  Option  Fibers.  The
          provisions  above shall be  applicable to the Option Fibers if WinStar
          exercises its Option.

8.       USE OF THE SYSTEM

     8.1. Use of WinStar Fibers.

          WinStar may use the WinStar Fibers for any lawful purpose.

     8.2. Notice of Damage.

          WinStar shall promptly  notify  Williams of any matters  pertaining to
          any damage or impending  damage to or loss of System that are actually
          known to it and that could  reasonably be expected to adversely affect
          the System.

     8.3. Precautions.

          WinStar  shall  take all  reasonable  precautions  against  any damage
          proximately caused by WinStar to the System or to fibers used or owned
          by Williams or third parties.

     8.4. Use of Equipment.

          Neither   party  shall  use,  or  allow  others  to  use,   equipment,
          technologies,  or  methods  of  operation  that  adversely  affect the
          Williams  Network or the System or the  permitted  use of the Williams
          Network or the System by Williams or third parties or their respective
          Fibers, equipment, or facilities associated therewith. If WinStar uses
          equipment,   technologies,   and   methods  of   operation   that  are
          collectively  either in accord with  Williams'  practices or generally
          accepted  industry  standards,  Williams  shall  have  the  burden  of
          demonstrating  that  WinStar  has  breached  the  requirements  of the
          preceding sentence. 

                                       21

<PAGE>

     8.5. Liens.

          WinStar  shall  not,  directly  or  indirectly,  cause any part of the
          System to become subject to any mechanic's lien,  materialman's  lien,
          vendor's  lien,  or any similar  lien  whether by  operation of law or
          otherwise.   If  WinStar  becomes  aware  that  it  has  breached  its
          obligations under this Section, it shall promptly:  notify Williams in
          writing,  cause  such lien to be  discharged  and  released  of record
          without cost to Williams and indemnify  Williams against all costs and
          expenses  (including  reasonable  attorneys'  fees and court  costs at
          trial and on appeal) incurred in discharging and releasing such lien.

9.       TERM

     9.1. Agreement Term.

          The term of this  Agreement  (the "Term") shall begin on the Effective
          Date and shall  end upon  expiration  of the last IRU Term to  expire,
          provided that,  with respect to the Interim IRU, the Term shall extend
          twenty-five years from the Effective Date.

     9.2. IRU Terms.

          The term of this Agreement in respect of each System Segment (the "IRU
          Term") shall begin on the applicable  Acceptance Date and shall end on
          the twenty-fifth (25th) anniversary of such Acceptance Date.

     9.3. Effect of Termination.

          No termination of this  Agreement,  an IRU Term, or of the Interim IRU
          shall affect the rights or obligations of any party hereto:

     (a)  With respect to any payment hereunder for services rendered during the
          Term; or

     (b)  Pursuant  to  Articles  14, 15,  16, 17, 18, 20, 23 and 24.1  entitled
          Audit Rights;  Indemnification;  Limitation  of Liability;  Insurance;
          Taxes and  Governmental  Fees;  Confidentiality;  Remedies and Dispute
          Resolution;  and Rules of Construction,  respectively.  

                                       22
<PAGE>

10. OPERATION, MAINTENANCE, AND REPAIR OF THE SYSTEM 

     10.1. Routine Maintenance.

          During the IRU Term,  Williams  shall  perform  all  required  Routine
          Maintenance at no additional  cost to WinStar.  "Routine  Maintenance"
          means the work  specifically  identified  as  Routine  Maintenance  in
          Exhibit I, provided that Routine  Maintenance  excludes work for which
          WinStar is obligated to reimburse Williams for all or a portion of the
          Costs incurred pursuant to other Articles of this Agreement (including
          the Fiber Collocation Provisions). 

     10.2. Non-Routine Maintenance.

          WinStar  shall pay its  Pro-Rata  Share of  Williams'  direct Costs of
          non-Routine  Maintenance  of the  System,  if the  Cost of  such  work
          relating  to any single  event or multiple  related  events is greater
          than five thousand dollars ($5,000.00). 

     10.3. Subcontractors.

          Williams may subcontract provisioning,  testing, maintenance,  repair,
          restoration,  relocation,  or other operational and technical services
          it is  obligated  to  provide  hereunder  or may have  the  underlying
          facility  owner  or its  contractor  perform  such  obligations.  Such
          subcontracting  shall not relieve  Williams of any  obligations  under
          this  Agreement.   

     10.4. Continued  Breach  of  Routine  Maintenance Obligations.

          Subject to the terms of Section 24.1(l), if, after the Acceptance Date
          for  any  System  Segment,  Williams  is in  material  breach  of  its
          obligation to provide  Routine  Maintenance  for a period of more than
          one hundred  twenty  (120)  consecutive  days after  WinStar  provides
          written notice of such breach, WinStar may deduct the following amount
          per month,  pro-rated for partial months, per each relevant Route mile
          from its monthly  invoice so long as that  material  breach  continues
          beyond such one hundred twenty (120) day period:  (i) seventy  dollars
          ($70)  per  month  prior to the  eighth  anniversary  of the  relevant
          Acceptance  Date,  (ii) ten  dollars  ($10) per month  from the eighth
          anniversary  of the relevant  Acceptance  Date up to but not including
          the tenth anniversary of the relevant  Acceptance Date, and (iii) five
          dollars ($5) per month thereafter. 

     10.5. WinStar Equipment.

          Williams'  maintenance  and repair  obligations  under this  Agreement
          shall not  include  maintenance,  repair  or  replacement  of  WinStar
          Equipment.

     10.6 Access to Systems.

          WinStar  shall not access  any  physical  part of any  System  Segment
          (other than pursuant to the Fiber Collocation  Provisions) without the
          prior  written  consent of Williams,  and then only upon the terms and
          conditions specified by Williams. 

                                       23

<PAGE>

11. RELOCATION 

     11.1. Relocation.

          If,  following the Acceptance  Date for any System  Segment,  Williams
          determines  for bona fide  operational  reasons,  or is  required by a
          third party acting pursuant to condemnation or similar authority or by
          a governmental  entity,  to relocate all or any portion of such System
          Segment or any of the facilities used or required in providing WinStar
          with the  WinStar  IRU,  Williams  shall,  to the extent  practicable,
          provide  WinStar sixty (60) days' prior notice of any such  relocation
          and shall proceed with such relocation.  Williams shall have the right
          to direct such relocation, including the right to determine the extent
          of,  the  timing  of,  and  methods  to be used for  such  relocation,
          provided that any such relocation:

          (a)  Shall  be   constructed   and  tested  in  accordance   with  the
               specifications  and  requirements set forth in this Agreement and
               applicable Exhibits;

          (b)  Shall  not  result  in  a  materially   adverse   change  to  the
               operations,  performance,  Connecting  Points with the network of
               WinStar, or end points of the System Segment; and

          (c)  Shall not unreasonably interrupt service on the System Segment.

          For purposes of this Section, a Williams' relocation shall be for bona
          fide  operational  reasons  if it is  undertaken  in good faith (i) to
          settle or avoid a bona fide threatened or filed condemnation action or
          order by a  governmental  authority  to  relocate,  (ii) to reduce the
          likelihood of physical damage to the System,  (iii) as the result of a
          Force Majeure Event,  or (iv) for other  operational  reasons to which
          WinStar has  consented,  provided that WinStar shall not  unreasonably
          withhold  such  consent.  Williams  shall use  reasonable  efforts  to
          contest any exercise of  condemnation  authority  that would require a
          relocation that would require WinStar to reimburse  Williams  pursuant
          to this Article 11.

     11.2. Cost of Relocation.

          Unless  such  relocation  is  necessitated  by a breach  of  Williams'
          obligations under this Agreement,  any Costs Williams incurs shall not
          be Routine Maintenance Costs, and WinStar shall reimburse Williams for
          the Costs incurred in the same manner and to the same extent as is set
          forth for  reimbursement of non-Routine  Maintenance  Costs in Section
          10.2. 

     11.3. Updated As-Built Drawings.

          At  WinStar's  written  request,  Williams  shall  deliver  to WinStar
          updated as-built  drawings with respect to a relocated  portion of the
          System  Segment  within  the later of  one-hundred  eighty  (180) days
          following the completion of such  relocation or thirty (30) days after
          receipt of WinStar's request. 

                                       24
<PAGE>

12. INVOICING AND PAYMENT 

     12.1. Due Date and Invoice.

          (a)  Payments of the Contract  Price and Exercise  Price shall be made
               in accordance with the Payment Terms.

          (b)  All amounts  stated on each  monthly  invoice are due and payable
               thirty  (30) days from  WinStar's  receipt of the  invoice  ("Due
               Date").  WinStar  agrees  to remit  payment  to  Williams  at the
               remittance  address set forth in the  applicable  invoice.  

     12.2. Form of Payment.

          WinStar  shall  pay the  Contract  Price  and  Exercise  Price by wire
          transfer of immediately  available  funds to the United States account
          or accounts  designated  by  Williams.  All other  payments to be made
          pursuant  to  this  Agreement  may  be  made  by  check  or  draft  of
          immediately  available  funds  delivered to the address  designated in
          writing by the other  party  (e.g.,  in a statement  or  invoice)  or,
          failing  such  designation,  to the  address  for notice to such other
          party provided pursuant to Article 19. 

     12.3. Disputed Charges.

          (a)  WinStar shall pay  undisputed  charges when such payments are due
               under this Agreement.  WinStar may withhold payment of particular
               charges  that  WinStar  disputes  in good  faith and for which it
               promptly gives written notice to Williams, stating the details of
               such  dispute.  The parties shall  promptly  refer such matter to
               dispute  resolution  in  accordance  with  Section 23. If WinStar
               withholds  any disputed  charges and such charges are  ultimately
               determined  to be proper and payable to Williams,  WinStar  shall
               pay such charges to Williams plus interest at the Prime Rate from
               the date such  charges  were  originally  due until the date such
               charges  are  paid.  No  payment  dispute  shall be  grounds  for
               Williams to  withhold or diminish  the quality or quantity of any
               of the connectivity and services provided hereunder.

          (b)  If WinStar  fails to pay  undisputed  charges  provided for under
               this  Agreement  when such  charges  are due,  Williams  may,  in
               addition  to any  other  remedies  that it may  have  under  this
               Agreement or by law,  terminate this Agreement only as it applies
               to the System Segment(s) or Telecommunications  Services to which
               such failure applies,  upon at least thirty (30) days' notice, if
               such  payment  (together  with  applicable  interest) is not made
               within such thirty (30) day notice  period  subject to  WinStar's
               thirty-day right to cure,  provided however,  that this remedy of
               termination  shall be available to Williams  only with respect to
               System  Segments for which the unpaid amount  exceeds two hundred
               thousand dollars ($200,000) at the time of such notice.

                                       25
<PAGE>

     12.4. Late Interest.

          If either  Williams or WinStar  fails to make any  payment  under this
          Agreement when due, such amounts shall accrue interest,  from the date
          such payment is due until paid,  including  accrued  interest,  at the
          Prime Rate. 

     12.5. Adjustments.

          Williams may make corrections to its invoices to reflect  undercharges
          only for the  period of two (2) years  following  the Due Date of each
          invoice, or two (2) years following the date the corresponding service
          is rendered,  whichever is later.  

13.  DISCLAIMER OF WARRANTIES 

     13.1. Parties.

          EXCEPT AS SPECIFICALLY  SET FORTH IN THIS AGREEMENT,  THE PARTIES MAKE
          NO  WARRANTY  TO EACH  OTHER OR ANY  OTHER  ENTITY,  WHETHER  EXPRESS,
          IMPLIED OR  STATUTORY,  AS TO THE  MERCHANTABILITY  OR FITNESS FOR ANY
          PARTICULAR PURPOSE OF ANY FIBERS,  THE SYSTEM, THE  TELECOMMUNICATIONS
          SERVICES,  ANY OTHER  SERVICES  OR ANY  ADDITIONAL  SERVICES  PROVIDED
          HEREUNDER OR DESCRIBED HEREIN, OR AS TO ANY OTHER MATTER, ALL OF WHICH
          WARRANTIES  ARE  HEREBY  EXPRESSLY  EXCLUDED  AND  DISCLAIMED.   

     13.2. Facility Owners/Lenders.

          NO FACILITY OWNERS/LENDERS HAVE MADE ANY REPRESENTATION OR WARRANTY OF
          ANY KIND,  EXPRESS OR IMPLIED,  TO WINSTAR  CONCERNING  WILLIAMS,  THE
          WINSTAR  FIBERS,  THE CABLE, OR THE SYSTEM OR AS TO ANY OF THE MATTERS
          SET FORTH IN SECTIONS  12.1 OR 24.2(a).  

14.  AUDIT  RIGHTS 

     Each party shall keep such books and records  (which shall be maintained on
     a consistent basis and substantially in accordance with generally  accepted
     accounting  principles) as shall readily disclose the basis for any charges
     (except  charges fixed in advance by this Agreement or by separate  written
     agreement of the parties) or credits, ordinary or extraordinary,  billed or
     due to the other party under this Agreement and shall make them  available,
     upon reasonable  notice and during normal working hours,  for  examination,
     audit,  and  reproduction by the other party and its agents for a period of
     one  (1)  year  after  such  charge  or  credit  is  billed  or  due.   

                                       26
<PAGE>

15. INDEMNIFICATION 

     15.1. Indemnification.

          Each party ("Indemnitor") shall indemnify,  defend,  protect, and hold
          harmless the other party, its employees,  members, managers, officers,
          agents,   contractors,   Facility   Owners/Lenders,   and   Affiliates
          (collectively and individually,  "Claimant"), from and against any and
          all Losses  resulting  or arising  from,  relating  to or  incurred in
          connection with:

          (a)  The  Indemnitor's  failure to  observe  or perform  its duties or
               obligations to third parties (e.g.,  duties or obligations to its
               customers);

          (b)  The Indemnitor's infringement or misappropriation of Intellectual
               Property Rights of any third party;

          (c)  The death or  bodily  injury of any  agent,  employee,  customer,
               business  invitee or any other person to the extent caused by the
               tortious conduct of the Indemnitor;

          (d)  The damage,  loss or destruction of any real or tangible personal
               property  to the  extent  caused by the  tortious  conduct of the
               Indemnitor;

          (e)  Fines, penalties or other amounts payable due to the Indemnitor's
               violation of applicable laws or regulation; and

          (f)  Any claim,  demand,  charge,  action,  cause of action,  or other
               proceeding  asserted  against the Claimant but resulting  from an
               act or omission of the  Indemnitor in its capacity as an employer
               of a person.

     15.2. Third Party Claims.

          With respect to third-party  claims,  the following  procedures  shall
          apply:  

          (a)  Promptly  after  receipt  of  notice  of  the   commencement   or
               threatened  commencement of any civil, criminal,  administrative,
               or  investigative  action  or  proceeding  involving  a claim  in
               respect of which the Claimant will seek indemnification  pursuant
               to this Article 15, the Claimant  will notify the  Indemnitor  of
               such claim in  writing.  No  failure to so notify the  Indemnitor
               will  relieve  the  Indemnitor  of  its  obligations  under  this
               Agreement  except to the extent  that its  ability to defend such
               claim is materially  prejudiced by such failure.  Within  fifteen
               (15) calendar days  following  receipt of written notice from the
               Claimant  relating  to any  claim,  but no  later  than  ten (10)
               calendar  days  before  the  date  on  which  any  response  to a
               complaint  or  summons is due,  the  Indemnitor  will  notify the
               Claimant in writing if the Indemnitor elects to assume control of
               the  defense  and   settlement   of  that  claim  (a  "Notice  of
               Election").

          (b)  If the Indemnitor  delivers a Notice of Election  relating to any
               claim within the required notice period,  the Indemnitor shall be
               entitled to have sole control over the defense and  settlement of
               such claim;  provided that (i) the Claimant  shall be entitled to
               observe  the  defense of such claim and to employ  counsel at its
               own expense to observe  the  defense of such claim,  and (ii) the
               Indemnitor  shall obtain the prior  written  approval,  not to be
               unreasonably  withheld or delayed, of the Claimant before ceasing
               to defend  against such claim or entering into any  settlement of
               such  claim.  After  the  Indemnitor  has  delivered  a Notice of
               Election  relating to any claim in accordance  with the preceding
               paragraph, the Indemnitor shall not be liable to the Claimant for
               any legal  expenses  incurred by the Claimant in connection  with
               the defense of that claim. In addition,  the Indemnitor shall not
               be  required to  indemnify  the  Claimant  for any amount paid or
               payable by the Claimant in the  settlement of any claim for which
               the  Indemnitor has delivered a timely Notice of Election if such
               amount  was  agreed  to  without  the  written   consent  of  the
               Indemnitor.

                                       27
<PAGE>

          (c)  If the Indemnitor does not deliver a Notice of Election  relating
               to  any  claim  within  the  required   notice  period  or  after
               delivering  a Notice of Election  fails to defend the claim,  the
               Claimant  shall have the right to defend the claim in such manner
               as  it  may  deem  appropriate.  The  Indemnitor  shall  promptly
               reimburse the Claimant for all  reasonable  costs and expenses of
               such defense. 

     15.3. Indemnification of Providers.

          WinStar shall indemnify and hold harmless Williams and any Third Party
          Service  Providers  from and  against  all  Losses  arising  out of or
          relating to the  content of any  transmission  by  WinStar,  including
          claims  relating  to any  violation  or  alleged  violation  of export
          control  laws or  other  laws or  failure  to  comply  with  WinStar's
          obligations as set forth in Sections 26.4 and 26.5.

15.4.    WinStar Customers.

          WinStar shall  indemnify  and hold Williams  harmless from and against
          all Losses arising out of or relating to the use of the WinStar Fibers
          by any WinStar customer.

16.  LIMITATION OF LIABILITY

     16.1. General Intent.

          Subject  to the  specific  provisions  of this  Article  16, it is the
          intent of the  Parties  that each  party  shall be liable to the other
          party for any actual damages incurred by the non-breaching  party as a
          result of the breaching  party's failure to perform its obligations in
          the manner required by this Agreement.

     16.2. Liability Restrictions.

          (a)  IN NO EVENT,  WHETHER IN CONTRACT OR IN TORT (INCLUDING BREACH OF
               WARRANTY, NEGLIGENCE AND STRICT LIABILITY IN TORT), SHALL A PARTY
               BE LIABLE FOR INDIRECT OR CONSEQUENTIAL,  EXEMPLARY,  PUNITIVE OR
               SPECIAL  DAMAGES  EVEN IF SUCH  PARTY  HAS  BEEN  ADVISED  OF THE
               POSSIBILITY OF SUCH DAMAGES IN ADVANCE.

                                       28
<PAGE>

          (b)  Subject to Subsection (c), below, each party's total liability to
               the other,  whether in contract or in tort  (including  breach of
               warranty,  negligence  and  strict  liability  in tort)  shall be
               limited to two hundred million dollars ($200,000,000).

          (c)  The  limitation set forth in Subsections  (b),  above,  shall not
               apply  with  respect  to:  (i)  third-party   claims  subject  to
               indemnification  pursuant  to the  Agreement;  (ii)  fees due and
               owing under this  Agreement  at the time of the claim;  and (iii)
               amounts subject of Cover as provided in Section 4.2(b).

          (d)  For the purposes of this  Section  16.2,  all amounts  payable or
               paid to third parties in connection with claims that are eligible
               for  indemnification  pursuant to this Agreement  shall be deemed
               direct damages.


     16.3. Released Parties.

          Neither party shall have any recourse of any kind against any Released
          Party or any assets of a  Released  Party in respect of any Claim that
          is not directly or indirectly  caused by the Released  Party, it being
          expressly  agreed and understood  that no liability  whatsoever  shall
          attach to or be incurred by any Released Party in respect of any Claim
          under  or by  reason  of  this  Agreement  or  any  other  instrument,
          arrangement or understanding  relating to the Network IRU, the System,
          the Interim IRU, the  Telecommunications  Services, the Other Services
          or Additional Services, except to the extent such Claim is directly or
          indirectly  caused by the Released  Party.  Each party waives all such
          recourse  to the  extent  set forth in this  Section  on behalf of its
          successors,  assigns,  and any entity claiming by,  through,  or under
          such party.

17.      INSURANCE

     17.1. Insurance.

          During the Term,  the parties  shall each obtain and maintain not less
          than the following insurance:

          (a)  Commercial  General Liability  Insurance,  including coverage for
               sudden and accidental pollution legal liability,  with a combined
               single limit of $10,000,000 for bodily injury and property damage
               per occurrence and in the aggregate.

          (b)  Worker's Compensation Insurance in amounts required by applicable
               law and Employers  Liability  Insurance with limits not less than
               $1,000,000  each accident.  If work is to be performed in Nevada,
               North Dakota,  Ohio,  Washington,  Wyoming or West Virginia,  the
               party shall participate in the appropriate state fund(s) to cover
               all eligible employees and provide a stop gap endorsement.

                                       29
<PAGE>

          (c)  Automobile  Liability  Insurance with a combined  single limit of
               $2,000,000 for bodily injury and property  damage per occurrence,
               to include coverage for all owned, non-owned, and hired vehicles.
          
     The limits set forth above are minimum limits and shall not be construed to
     limit the liability of either party.

     17.2. Documentation.

          (a)  Each party  shall  obtain and  maintain  the  insurance  policies
               required  above with  companies  rated A- or better by Best's Key
               Rating  Guide  or with a  similar  rating  by  another  generally
               recognized  rating  agency.  The  other  party,  its  Affiliates,
               officers,  directors, and employees, and any other party entitled
               to  indemnification   hereunder  shall  be  named  as  additional
               insureds to the extent of such indemnification.  Each party shall
               provide the other party with an insurance certificate  confirming
               compliance with the insurance  requirements of this Article.  The
               insurance  certificate  shall indicate that the other party shall
               be  notified  not  less  than  thirty  (30)  days  prior  to  any
               cancellation or material change in coverage.

          (b)  If either party provides any of the foregoing coverages through a
               claims made policy  basis,  that party shall cause such policy or
               policies to be maintained for at least three (3) years beyond the
               expiration of this Agreement.

     17.3. Certificates.

          The parties shall each obtain from the insurance  companies  providing
          the  coverages  required  by this  Agreement a waiver of all rights of
          subrogation   or  recovery  in  favor  of  the  other  party  and,  as
          applicable,   its   members,   managers,   shareholders,   Affiliates,
          assignees,  officers,  directors,  and  employees  or any other  party
          entitled  to  indemnity  under  this  Agreement  to the extent of such
          indemnity.

     17.4. Blanket Policies.

          Nothing in this  Agreement  shall be construed to prevent either party
          from satisfying its insurance  obligations  pursuant to this Agreement
          under a blanket  policy or policies of  insurance  that meet or exceed
          the requirements of this Article.

18.      TAXES AND GOVERNMENTAL FEES

     18.1. Payment by WinStar.

          WinStar  shall timely report and pay any and all sales,  use,  income,
          gross receipts,  excise, transfer, ad valorem, or other taxes, and any
          and all franchise  fees or similar fees, if any,  assessed  against it
          due to its  ownership  of the  Network  IRU,  its  use of the  WinStar
          Fibers,  including the provision of services over the WinStar  Fibers,
          its use of any other part of the System,  or its  ownership  or use of
          facilities connected to the WinStar Fibers.

                                       30
<PAGE>


     18.2. Payment by Williams.

          Subject to Section 18.1 above,  Williams  shall timely  report and pay
          any and all sales, use, income, gross receipts,  excise,  transfer, ad
          valorem or other taxes, and any and all franchise fees or similar fees
          assessed against it due to its  construction,  ownership or use of the
          System,  provided  that  WinStar  shall  reimburse  Williams  for  its
          Pro-Rata Share of property taxes (including ad valorem, use, property,
          or similar taxes, franchise fees, or assessments that are based on the
          value of property or of a property right)  attributable to the System,
          including  taxes based on the value,  operation,  or  existence of the
          System.

     18.3. Reimbursement.

          If Williams is assessed for any taxes or fees (a) related to WinStar's
          ownership  of the  Network  IRU,  WinStar's  use of or  rights  in the
          WinStar  Fibers,  or (b) that  WinStar is obligated to pay pursuant to
          Sections  18.1 or  18.2,  WinStar  shall  reimburse  Williams  for any
          payment of such taxes or fees  within  thirty  (30) days of receipt of
          Williams' invoice.

     18.4. Cooperation.

          The parties shall  cooperate in any contest of any taxes or fees so as
          to avoid, to the extent reasonably possible, prejudicing the interests
          of the other party.

     18.5. Services.

          If  any  sales  taxes,  valued  added  taxes  or  similar  charges  or
          impositions  are assessed  against  Williams after, or as a result of,
          WinStar's use of  Telecommunications  Services,  any Other Services or
          the Additional Services by any local, state, national,  international,
          public or quasi-public  governmental  entity or foreign  government or
          its  political  subdivision,  including  any tax or  charge  levied to
          support   the   Universal    Service   Fund    contemplated   by   the
          Telecommunications  Act of 1996,  WinStar shall be solely  responsible
          for and shall pay such taxes, charges or impositions and hold Williams
          harmless  from any  liability or expense  associated  with such taxes,
          charges or impositions.

19.  NOTICE

     Unless otherwise provided in this Agreement, all notices and communications
     concerning  this  Agreement  shall be in writing and addressed to the other
     party as follows,  or at such other address as may be designated in writing
     to the other party:


         If to WinStar:                      If to Williams:
               WinStar Wireless, Inc.           Williams Communications, Inc.
               230 Park Avenue                  One Williams Center, Suite 26-5
               New York, NY  10169              Tulsa, Oklahoma  74172
               Attn:  EVP, General Counsel      Attn:  Contract Administration
               Facsimile:  212/922-1637         Facsimile:  918/573-6578

                                       31
<PAGE>

         With a copy to:                     With a copy to:
            WinStar Wireless, Inc.              Williams Communications, Inc.
            7799 Leesburg Pike                  One Williams Center, Suite 4100
            Falls Church, Virginia 22043        Tulsa, Oklahoma  74172
            Attn:  VP, Commercial and           Attn:  General Counsel
               Legal Operations               
            Facsimile:  703/288-6647            Facsimile:  918/573-3005

          Unless  otherwise  provided  herein,  notices shall be hand delivered,
          sent by registered or certified  U.S.  Mail,  postage  prepaid,  or by
          commercial  overnight  delivery service,  or transmitted by facsimile,
          and shall be deemed served or delivered to the addressee or its office
          when  received  at the address  for notice  specified  above when hand
          delivered, upon confirmation of sending when sent by facsimile, on the
          day after being sent when sent by overnight  delivery  service,  three
          (3) days after  deposit in the mail when sent by U.S.  mail or, in the
          case  of   invoices,   upon   the  Due  Date   (as   defined   in  the
          Telecommunications Services Purchase Provision).

20.  CONFIDENTIALITY

     20.1. Confidential Information.

          Williams and WinStar each acknowledge that they may be furnished with,
          receive,  or otherwise have access to information of or concerning the
          other party that such party considers to be confidential, proprietary,
          a trade secret or otherwise restricted.  As used in this Agreement and
          subject  to  Section  20.3,   "Confidential   Information"  means  all
          information,  in any form,  furnished  or made  available  directly or
          indirectly  by one party  (the  "Disclosing  Party") to the other (the
          "Receiving  Party")  that (i)  concerns  the  operations,  facilities,
          plans,  affairs and businesses of the Disclosing  Party, the financial
          affairs of the Disclosing  Party,  and the relations of the Disclosing
          Party with its customers,  employees and service providers, or (ii) is
          marked  confidential,  restricted,  proprietary,  or  with  a  similar
          designation.  The  terms and  conditions  of this  Agreement  shall be
          deemed  Confidential  Information,  but may be  disclosed  as provided
          below and Section 24.6.

     20.2. Obligations.

          (a)  Each party's  Confidential  Information shall remain the property
               of that party except as expressly provided otherwise by the other
               provisions of this Agreement.  Each party shall each use at least
               the  same  degree  of  care,  but in any  event  no  less  than a
               reasonable degree of care, to prevent unauthorized  disclosure of
               Confidential  Information  as it  employs  to avoid  unauthorized
               disclosure of its own information of a similar nature.  Except as
               otherwise  permitted  hereunder,  the parties may  disclose  such
               information  (A)  to  their   respective   directors,   officers,
               managers,   employees,   agents,   contractors   and  consultants
               (collectively,  "Representatives")  and (B)  entities  performing
               services required hereunder only where: (i) use of such entity is
               authorized   under  this  Agreement,   (ii)  such  disclosure  is
               necessary or otherwise naturally occurs in that entity's scope of
               responsibility,  and (iii) the entity agrees in writing to assume
               the obligations described in this Section 20.2. Any disclosure to
               such entity shall be under substantially the same confidentiality
               terms and conditions as provided herein.

                                       32
<PAGE>

          (b)  Each party  shall take  reasonable  steps to ensure that its (and
               its Affiliates')  Representatives  comply with this Section 20.2.
               In the  event of any  disclosure  or loss  of,  or  inability  to
               account  for,  any  Confidential  Information  of the  Disclosing
               Party,  the Receiving Party shall  promptly,  at its own expense:
               (i)  notify  the  Disclosing  Party in  writing;  (ii)  take such
               actions  as may be  necessary  and  cooperate  in all  reasonable
               respects with the Disclosing  Party to minimize the violation and
               any damage resulting therefrom.

          (c)  Either  party  may  disclose  the terms  and  conditions  of this
               Agreement  to any third party that (i) has  expressed a bona fide
               interest  in  consummating  a  significant  financing,  merger or
               acquisition  transaction or other corporate  transaction  between
               the third party and such  party,  (ii) has a  reasonable  ability
               (financial  or otherwise) to  consummate  such  transaction,  and
               (iii) has executed a nondisclosure agreement that includes within
               its scope the terms and  conditions  of this  Agreement  and also
               includes  a  procedure   to  limit  the  extent  of  copying  and
               distribution  thereof.  Each party  shall  endeavor  to delay the
               disclosure of the terms and  conditions of this  Agreement  until
               the status of discussions  concerning such  transaction  warrants
               such  disclosure.  In addition,  either party (or either  party's
               Affiliates)  may  disclose  the  terms  and  conditions  of  this
               Agreement as such party deems  appropriate to prepare for IPOs or
               major corporate transactions. Any disclosure to such entity shall
               be  substantially  under  the  same  confidentiality   terms  and
               conditions as provided herein.

     20.3. Exclusions.

          "Confidential  Information"  shall exclude any particular  information
          that the Receiving Party can demonstrate:

          (a)  At the time of  disclosure,  was in the  public  domain or in the
               rightful possession of the Receiving Party;

          (b)  After  disclosure,  is published or otherwise becomes part of the
               public domain through no fault of the Receiving Party;

          (c)  Was received after disclosure from a third party who had a lawful
               right to disclose such information to the Receiving Party without
               any obligation to restrict its further use or disclosure; 

                                       33
<PAGE>

          (d)  Was  independently  developed  by  the  Receiving  Party  without
               reference to Confidential Information of the Disclosing Party; or

          (e)  Was required to be disclosed to satisfy a legal  requirement of a
               competent  government  body;  provided  that,   immediately  upon
               receiving  such  request and to the extent that it may legally do
               so, the Receiving Party advises the Disclosing Party promptly and
               prior to making  such  disclosure  in order  that the  Disclosing
               Party may interpose an objection to such disclosure,  take action
               to assure confidential handling of the Confidential  Information,
               or take such other action as it deems  appropriate to protect the
               Confidential Information.

     20.4. No Implied Rights.

          Nothing  contained in this Section  shall be construed as obligating a
          party to disclose its Confidential  Information to the other party, or
          as granting to or conferring on a party,  expressly or impliedly,  any
          rights or license to the Confidential Information of the other party.

     20.5  Communication With FCC.

          Communications  by either  party with the FCC  regarding  the  subject
          matter of this  Agreement  shall  require  the other's  prior  written
          approval.

21 . DEFAULT

     A party shall not be in material breach of this Agreement  unless and until
     the  other   party   provides   it  written   notice  of  default  and  the
     non-performing  party has  failed to cure  within  thirty  (30) days  after
     receipt of such  notice.  Any event of default  may be waived in writing at
     the  non-defaulting  party's option.  Upon the failure of a party to timely
     cure its material breach hereunder  within the applicable cure period,  the
     non-defaulting  party shall have the right to (i) terminate  this Agreement
     or (ii)  subject to the terms of Article 23,  pursue any legal  remedies it
     may have under  applicable  law or  principles  of equity  relating to such
     breach.

22.  FORCE MAJEURE

     22.1. Excusable Delay.

          Neither  Williams nor WinStar shall be in default under this Agreement
          as a result of any delay in its  performance  (other than a failure to
          make  payments  when due) caused by any  elements of nature or acts of
          God, fire, explosion,  vandalism, power outage,  earthquake,  flood or
          lightning;  any civil or military  authority;  by national  emergency,
          insurrection, rebellion, revolution, riot, civil disorders, war or act
          of terrorism;  by cable cuts; or any other cause beyond the reasonable
          control  of  such  party   (collectively,   "Force  Majeure  Events");
          provided,  however, that (i) the non-performing party is without fault
          in causing such default or delay, and (ii) such default or delay could
          not  have  been  prevented  by  reasonable   precautions   and  cannot
          reasonably be circumvented by the non-performing party through the use
          of alternate  sources  (e.g.,  other  suppliers of  telecommunications
          services or  capacity),  workaround  plans or other  means,  including
          means  contemplated  by  applicable  disaster  recovery  processes  or
          procedures).

                                       34
<PAGE>

     22.2. Notice and Remedy.

          In such event the  non-performing  party shall be excused from further
          performance or observance of the obligation(s) so affected for as long
          as  such  circumstances  prevail  and  such  party  continues  to  use
          commercially   reasonable   efforts  to  recommence   performance   or
          observance whenever and to whatever extent possible without delay. The
          non-performing  party  shall  immediately  notify  the other  party by
          telephone (to be confirmed in writing  within two (2) business days of
          the  inception of such delay) and  describe at a  reasonable  level of
          detail the Force  Majeure  Event  causing  such delay and the expected
          duration of the Force Majeure  Event.  The  non-performing  party will
          provide the other party  prompt  written  notice of the  cessation  or
          termination of the Force Majeure Event.

23.  REMEDIES AND DISPUTE RESOLUTION

     23.1. Dispute Resolution.

          Any dispute  between  the  Parties  arising out of or relating to this
          Agreement,   the   interpretation  of  any  provision  hereof  or  the
          performance  or failure to perform  of  Williams  or WinStar  shall be
          resolved as provided in this Article 23.

     23.2. Cumulative Remedies.

          Except as otherwise  expressly  provided herein, all remedies provided
          for in this  Agreement  shall be cumulative and in addition to and not
          in lieu of any other  remedies  available  to either  party at law, in
          equity or otherwise.

     23.3. Informal Dispute Resolution.

          (a)  Prior to the initiation of formal dispute  resolution  procedures
               (i.e.,  arbitration),  the parties shall first attempt to resolve
               their  dispute  at the  senior  manager  level.  If that level of
               dispute  resolution is not successful,  the parties shall proceed
               informally, as follows:

               (i)  Upon the written  request of either party,  each party shall
                    appoint a designated  representative  who does not otherwise
                    devote  substantially  full time to  performance  under this
                    Agreement,  whose task it will be to meet for the purpose of
                    endeavoring to resolve such dispute.

               (ii) The  designated  representatives  shall meet as often as the
                    parties  reasonably  deem  necessary  in order to gather and
                    furnish  to the other all  information  with  respect to the
                    matter in issue that the parties  believe to be  appropriate
                    and  germane  in  connection   with  its   resolution.   The
                    representatives  shall  discuss  the  problem and attempt to
                    resolve the  dispute  without  the  necessity  of any formal
                    proceeding.

                                       35
<PAGE>

               (iii)During the course of  discussion,  all  reasonable  requests
                    made   by  one   party   to   another   for   non-privileged
                    non-confidential  information  reasonably  related  to  this
                    Agreement  shall be honored so that each of the  parties may
                    be fully advised of the other's position.

               (iv) The specific format for the discussions shall be left to the
                    discretion of the designated representatives. 

          (b)  Prior to instituting formal  proceedings,  the parties will first
               have their chief executive  officers meet to discuss the dispute.
               This  requirement  shall  not  delay  the  institution  of formal
               proceedings  past any statute of  limitations  expiration  or for
               more than fifteen (15) days.

          (c)  Subject to Subsection (b), formal  proceedings for the resolution
               of a dispute may not be  commenced  until the earlier of: 

               (i)  The designated representatives concluding in good faith that
                    amicable  resolution  through  continued  negotiation of the
                    matter does not appear likely; or

               (ii) Thirty  (30)  days  after the  initial  written  request  to
                    appoint a designated  representative  pursuant to Subsection
                    (a),   above,   (this   period   shall  be   deemed  to  run
                    notwithstanding any claim that the process described in this
                    Section 23.3 was not followed or completed).

          (d)  This  Section 23.3 shall not be construed to prevent a party from
               instituting,  and a party  is  authorized  to  institute,  formal
               proceedings  earlier to avoid the  expiration  of any  applicable
               limitations  period,  or to  preserve  a superior  position  with
               respect to other creditors or as provided in Section 23.6.

     23.4. Arbitration.

          If the  Parties  are unable to resolve a dispute  as  contemplated  by
          Section 23.3,  then except as provided by Section  23.6,  such dispute
          shall  be  submitted  to  mandatory  and  binding  arbitration  at the
          election  of  either  WinStar  or  Williams  (the  "Disputing  Party")
          pursuant to the following conditions:

          (a)  The  Disputing  Party  shall  notify  the  American   Arbitration
               Association ("AAA") and the other party, describing in reasonable
               detail the nature of the  dispute  (the  "Dispute  Notice");  and
               shall  request  that the AAA furnish a list of five (5)  possible
               arbitrators    who   have    substantial    experience   in   the
               telecommunications  industry.  Each party shall have fifteen (15)
               days to reject two (2) of the proposed  arbitrators.  If only one
               individual  has not been so rejected,  that person shall serve as
               arbitrator;  if two  (2) or more  individuals  have  not  been so
               rejected,   the  AAA  shall  select  the  arbitrator  from  those
               individuals.

                                       36

<PAGE>

          (b)  The  arbitration  shall  take  place  in  Chicago,  Illinois,  in
               accordance with the Commercial  Arbitration Rules of the American
               Arbitration Association in effect on the date that such notice is
               provided.   The  arbitration  shall  be  commenced  promptly  and
               conducted expeditiously.  The parties shall be entitled to submit
               expert testimony and/or written documentation on such arbitration
               proceeding.  The  decision of the  arbitrator  shall be final and
               binding  upon  Williams  and  WinStar and shall  include  written
               findings of law and fact, and judgment may be obtained thereon by
               either Williams or WinStar in a court of competent  jurisdiction.
               Williams and WinStar  shall each bear the cost of  preparing  and
               presenting its own case. The cost of the  arbitration,  including
               the fees and expenses of the arbitrator,  shall be shared equally
               by Williams and WinStar unless the award otherwise provides.  The
               arbitrator shall be instructed to establish  procedures such that
               a  decision  can  be  rendered  within  sixty  (60)  days  of the
               appointment of the arbitrator.

          (c)  The  obligation to arbitrate  shall not be binding upon any party
               with respect to requests for preliminary  injunctions,  temporary
               restraining orders, specific performance,  or other procedures in
               a court of competent  jurisdiction  to obtain interim relief when
               deemed  necessary  by such  court to  preserve  the status quo or
               prevent  irreparable  injury pending resolution by arbitration of
               the actual dispute.

          (d)  Any arbitrator  appointed to act under this Article must agree to
               be bound by the provisions of this Agreement and any  information
               obtained  during the course of the  arbitration  proceedings.  In
               particular,  the  arbitrator  shall  not  have the  authority  to
               exclude the right of a Party to terminate  this  Agreement when a
               Party would otherwise have such right.  The  arbitration  hearing
               shall be commenced promptly and conducted expeditiously.

          (e)  Should  the  arbitrator  refuse  or be  unable  to  proceed  with
               arbitration  proceedings  as  called  for by this  Section,  such
               arbitrator  shall be replaced and a rehearing shall take place in
               accordance with the provisions of this Section. In such case, the
               replacement  for the arbitrator  shall be either  selected by the
               AAA from the original  group of potential  arbitrators  that were
               not rejected by the parties or, if there are no such  arbitrators
               available,   selected  by  repeating  the  process  of  selection
               described in 23.4(a).

          (f)  The  arbitrator is instructed  that time is of the essence in the
               arbitration  proceeding,  and that the arbitrator  shall have the
               right and authority to issue monetary sanctions against either of
               the  parties  if,  upon a showing  of good  cause,  that party is
               unreasonably  delaying the  proceeding.  Recognizing  the express
               desire  of  the  parties  for an  expeditious  means  of  dispute
               resolution,  the  arbitrator  shall limit or allow the parties to
               expand  the scope of  discovery  as may be  reasonable  under the
               circumstances.

                                       37
<PAGE>

     23.5. Continued Performance.

          Each party agrees to continue  performing its  obligations  under this
          Agreement while any dispute is being resolved except to the extent the
          issue in dispute precludes performance.

     23.6. Immediate Injunctive Relief.

          The only  circumstance in which disputes between the parties shall not
          be  subject  to the  provisions  of  Section  23.3 and 23.4 is where a
          party, in good faith, determines that a temporary restraining order or
          other  injunctive  relief is its only appropriate and adequate remedy.
          If a party seeks immediate  injunctive  relief and does not prevail in
          substantial  part,  that party shall pay the other  party's  costs and
          attorneys' fees to the extent incurred in responding to or challenging
          the request for immediate injunctive relief.

24.  GENERAL

     24.1. Rules of Construction.

          (a)  The  captions or  headings in this  Agreement  are  strictly  for
               convenience  and shall not be  considered  in  interpreting  this
               Agreement or as amplifying or limiting any of its content.  Words
               in this Agreement that import the singular  connotation  shall be
               interpreted   as  plural,   and  words  that  import  the  plural
               connotation shall be interpreted as singular,  as the identity of
               the parties or objects  referred to may  require.  References  to
               "person"  or  "entity"  each  include  natural  persons and legal
               entities,  including  corporations,  limited liability companies,
               partnerships,    sole   proprietorships,    business   divisions,
               unincorporated  associations,   governmental  entities,  and  any
               entities  entitled  to bring an action in, or that are subject to
               suit in an  action  before,  any  state or  federal  court of the
               United States.

          (b)  Unless  expressly   defined  herein,   words  having   well-known
               technical or trade meanings shall be so construed.

          (c)  Except as set forth to the contrary  herein,  any right or remedy
               of Williams or WinStar shall be cumulative and without  prejudice
               to any other right or remedy, whether contained herein or not.

          (d)  Nothing in this Agreement is intended to provide any legal rights
               to anyone not an executing  party of this Agreement  except under
               the indemnification and insurance  provisions and except that (i)
               the  Released  Parties  shall have the benefit of Sections  16.3,
               24.2(a) and 24.5(a) and (ii) the Facility Owners/Lenders shall be
               entitled  to rely on and have the  benefit of  Sections  13.2 and
               24.5(b).

                                       38
<PAGE>

          (e)  This  Agreement has been fully  negotiated  between  Williams and
               WinStar.

          (f)  In the  event  of a  conflict  between  the  provisions  of  this
               Agreement  and  those  of any  Exhibit,  the  provisions  of this
               Agreement  shall  prevail  and such  Exhibit  shall be  corrected
               accordingly,  provided  that the  provisions  of  Exhibit K shall
               prevail over  conflicting  provisions  in the Agreement or in any
               Exhibit. Notwithstanding the above, terms defined in Section 7 of
               Exhibit K shall not  supersede  terms defined in the Agreement or
               in other Exhibits except as used in Exhibit K.

          (g)  Except as  otherwise  set forth  herein,  for the purpose of this
               Agreement  the  normal   standards  of  performance   within  the
               telecommunications  industry in the relevant  market shall be the
               measure  of  whether  a party's  performance  is  reasonable  and
               timely.

          (h)  Except as the context  otherwise  indicates,  all  references  to
               Exhibits,   Articles,   Sections,   Subsections,   Clauses,   and
               Paragraphs refer to provisions of this Agreement.

          (i)  The  failure of either  Williams or WinStar to enforce any of the
               provisions  of  this  Agreement,  or the  waiver  thereof  in any
               instance,   shall  not  be  construed  as  a  general  waiver  or
               relinquishment  on its part of any such  provision,  but the same
               shall nevertheless be and remain in full force and effect.

          (j)  This  Agreement  shall be governed by and construed in accordance
               with the domestic laws of the State of New York without reference
               to its  choice  of  law  principles.  All  disputes  referred  to
               arbitration  and the statute of limitations  and the remedies for
               any wrongs  that may be found  shall be  governed  by the laws of
               such state.  If a proceeding  is brought for the  enforcement  of
               this  Agreement  or  because of any  alleged  or actual  dispute,
               breach,  default or  misrepresentation  in connection with any of
               the provisions of this Agreement,  the prevailing  party shall be
               entitled to recover  reasonable  attorneys'  fees and other costs
               and expenses incurred in such action or proceeding in addition to
               any other relief to which such party may be entitled.

          (k)  If any term,  covenant or condition in this Agreement  shall,  to
               any extent,  be invalid or unenforceable in any respect under the
               laws  governing this  Agreement,  the remainder of this Agreement
               shall  not be  affected  thereby,  and  each  term,  covenant  or
               condition of this Agreement shall be valid and enforceable to the
               fullest extent permitted by law.

          (l)  The  parties   acknowledge   and  agree  that:  (i)  the  payment
               deductions  ("Payment  Deductions") set forth in Sections 5.2(g),
               6.1(c) and 10.4  (collectively,  the "Deduction  Sections") shall
               not limit  Williams'  liability  or serve as a sole or  exclusive
               remedy for Williams' default under any portion of this Agreement;
               (ii)  WinStar  may seek any other  rights or remedies it may have
               against  Williams  for any default  hereunder;  (iii) none of the
               Deduction  Sections  modify or otherwise  limit any other term or
               condition  of this  Agreement;  (iv) the one  hundred  and twenty
               (120) day periods specified in the Deduction  Sections shall only
 
                                       39
<PAGE>


               be  applicable  with respect to the  Deduction  Sections and such
               periods shall in no manner whatsoever be construed or interpreted
               to extend  Williams'  cure  periods or other  timing of any other
               obligation  set forth in any other  provision of this  Agreement;
               and (v) WinStar's  compliance  with the Deduction  Sections shall
               not  constitute a breach of the Payment  Terms.  Williams  hereby
               waives any rights it may have to use the Deduction  Sections as a
               claim or defense against any other provision in this Agreement.

     24.2. Assignment.

          (a)  Except to the extent permitted by Section 24.2(d),  neither party
               may,  or shall  have the  power  to,  assign  this  Agreement  or
               delegate  such party's  obligations  hereunder  without the prior
               written consent of the other except to:

               (i)  An entity  that  acquires  all or  substantially  all of the
                    assets of such party,

               (ii) Any Affiliate,

               (iii) A successor in a merger or acquisition of such party, or

               (iv) In connection with any financing.

          (b)  Notwithstanding the foregoing, no assignment or other transfer of
               this Agreement shall be effective  without the written  agreement
               of the assignee to be bound by the terms and  conditions  of this
               Agreement   including   the   indemnification    provisions   and
               limitations on liability and recourse set forth in this Agreement
               (including those benefiting the Released Parties).

          (c)  Except  with  respect  to the  assignment  of less  than all of a
               party's rights or obligations  under this Agreement and except as
               set forth in Section 24.2(e),  the non-assigning  party shall not
               unreasonably withhold its consent to an assignment if neither the
               assigning party nor the proposed  assignee is in material default
               under   this   Agreement   or  any  other   agreement   with  the
               non-assigning party.

          (d)  The provisions of Section 24.2(a)  notwithstanding,  Williams may
               assign  some or all of its rights and  obligations  hereunder  to
               State  Street  Bank and Trust  Company of  Connecticut,  National
               Association,  in  connection  with a  financing  by  Williams  of
               construction  of its fiber  optic  network;  in  addition,  State
               Street   Bank  and  Trust   Company  of   Connecticut,   National
               Association,  may further assign this Agreement as collateral for
               such financing.  If Williams makes an assignment pursuant to this
               Subsection  24.2(d),  Williams  (or its  assignee  pursuant to an
               assignment made under the other  provisions of this Section 24.2)
               shall guarantee performance of the assignee's obligations.

                                       40
<PAGE>

          (e)  Except in  connection  with an  assignment  of this  Agreement as
               provided  herein,  until  the  third  (3rd)  anniversary  of  the
               Acceptance Date of any System Segment, WinStar shall not sell the
               dark fiber,  raw frequency  (commonly known as "windows") but may
               place optronics in such System Segment and resell capacity in any
               increment.  After such three (3) year period,  WinStar may convey
               such an interest  provided  that WinStar  shall serve as the sole
               point  of  contact  with  Williams  and no party  receiving  such
               interest shall have any contract  rights against or be in privity
               of contract with Williams as a result of such conveyance.

          (f)  This  Agreement  and  the  rights  and  obligations   under  this
               Agreement  (including  the  limitations on liability and recourse
               set forth in this  Agreement  benefiting  the other party and the
               Released  Parties)  shall be binding  upon and shall inure to the
               benefit of Williams  and WinStar and their  respective  permitted
               successors and assigns.

          (g)  Neither the  provisions of this Article nor any other  provisions
               of  this  Agreement  shall  limit  the  ability  of any  Facility
               Owners/Lenders  or of any Released Parties to assign their rights
               under  this  Agreement  and  such  Facility   Owners/Lenders  and
               Released  Parties may assign their  rights  hereunder at any time
               and from time to time  without the consent of,  notice to, or any
               other  action  by  any  other  entity.  The  provisions  of  this
               Agreement  benefiting  the Facility  Owners/Lenders  and Released
               Parties  shall  inure to the benefit of such  entities  and their
               respective Affiliates, successors, and assigns.

          (h)  Notwithstanding  any presumptions under applicable state law that
               a change in control of a party  constitutes  an  assignment of an
               agreement,  a change in control of a party, not made for purposes
               of  circumventing  restrictions on assignment or of depriving the
               other party of rights under this  Agreement,  shall not be deemed
               an assignment for purposes of this Agreement.

     24.3. Relationship of the Parties.

          The  relationship  between  Williams and WinStar  shall not be that of
          partners,  agents,  or joint  venturers  for one another,  and nothing
          contained  in  this   Agreement   shall  be  deemed  to  constitute  a
          partnership  or  agency  agreement  between  them  for  any  purposes,
          including  federal  income tax  purposes.  Williams  and  WinStar,  in
          performing any of their  obligations  hereunder,  shall be independent
          contractors  or  independent   parties  and  shall   discharge   their
          contractual obligations at their own risk.

     24.4. Prohibition on Improper Payments.

          Neither party shall use any funds  received  under this  Agreement for
          illegal or otherwise "improper" purposes.  Neither party shall pay any
          commission,  fees or rebates to any  employee of the other  party.  If
          either  party  has  reasonable  cause  to  believe  that  one  of  the

                                       41
<PAGE>

          provisions   in  this   Article   has  been   violated,   it,  or  its
          representative, may audit the books and records of the other party for
          the sole purpose of establishing compliance with such provisions.

     24.5. Entire Agreement; Amendment; Execution.

          (a)  This  Agreement  constitutes  the entire and final  agreement and
               understanding  between  Williams  and WinStar with respect to the
               subject matter hereof and supersedes all prior  agreements  (oral
               or written)  relating to the subject matter hereof,  which are of
               no  further  force  or  effect  (including,  in  particular,  the
               Customer Services Agreement between Williams and WinStar GoodNet,
               dated July 16, 1998,  Contract Number  98R0675.00,  provided that
               any  undisputed  payment   obligations   accruing  prior  to  the
               Effective  Date,  shall be due and owing  under the terms of this
               Agreement).  The Exhibits  referred to herein are integral  parts
               hereof and are made a part of this Agreement by reference.

          (b)  This Agreement may only be amended,  modified, or supplemented by
               an instrument  in a single  writing  executed by duly  authorized
               representatives  of  Williams  and  WinStar.  No such  amendment,
               modification,  or supplement  shall result in any modification of
               (i) any indemnity benefiting any Facility Owners/Lenders or their
               respective  Affiliates  or (ii) any  limitation  of  liability or
               recourse  benefiting any Released Parties that is adverse to such
               Released Parties.

          (c)  This Agreement may be executed in one or more  counterparts,  all
               of  which  taken  together  shall  constitute  one and  the  same
               instrument.

          (d)  This  Agreement  may be duly executed and delivered by a party by
               execution  and  facsimile  delivery  of the  signature  page of a
               counterpart  to the other party,  provided  that,  if delivery is
               made by facsimile,  the executing party shall promptly  deliver a
               complete counterpart that it has executed to the other party.

          (e)  Unless otherwise expressly permitted in this Agreement,  Williams
               shall not make any changes to the Exhibits or Schedules  attached
               hereto that may have a material adverse impact on the performance
               or  usability  of  the  Telecommunications  Services,  Additional
               Services  or  Other  Services  without  WinStar's  prior  written
               consent.

     24.6 Public Disclosures.

          All media  releases,  public  announcements,  and  public  disclosures
          relating to this  Agreement or the subject  matter of this  Agreement,
          including  promotional  or  marketing  material,   but  not  including
          announcements intended solely for internal distribution or disclosures
          to the extent required to meet legal or regulatory  requirements shall
          be  coordinated  with and shall be subject to approval by both parties
          prior to release.

                                       42
<PAGE>

25.  REPRESENTATIONS, WARRANTIES AND COVENANTS

     25.1. Representations and Warranties.

          In addition to any other  representations and warranties  contained in
          this Agreement, each party hereto represents and warrants to the other
          that:

          (a)  It has the  requisite  corporate  power to enter  into,  execute,
               deliver, and perform its obligations under this Agreement;

          (b)  It has taken  all  requisite  corporate  action  to  approve  the
               execution, delivery, and performance of this Agreement;

          (c)  This Agreement  constitutes a legal, valid and binding obligation
               enforceable against such party in accordance with its terms;

          (d)  Its execution of and  performance  under this Agreement shall not
               violate any applicable existing regulations,  rules, statutes, or
               court orders of any local,  state, or federal  government agency,
               court, or body;

          (e)  It is not subject to any  contractual  or other  obligation  that
               would prevent it from entering into this relationship;  and 

          (f)  It has not offered or provided  any  inducements  in violation of
               law or the other  party's  policies,  of which it has been  given
               notice,  in  connection  with this  Agreement.  

     25.2. Additional Williams Covenants.

          Excluding  services  provided by third  parties  other than  Williams'
          subcontractors,  Williams covenants that Telecommunications  Services,
          Additional  Services,  and Other Services shall be provided to WinStar
          in  accordance  with  the  technical   parameters  set  forth  in  the
          applicable service schedule.  Williams further covenants that it shall
          use commercially  reasonable efforts under the circumstances to remedy
          any delays, interruptions, omissions, mistakes, accidents or errors in
          the Telecommunications Services, Additional Services or Other Services
          provided hereunder and to restore such Telecommunications  Services or
          Other Services to compliance with the terms hereof.

     25.3. Infringement of Intellectual Property Rights.

          Each party  represents,  warrants  and  covenants to the other that it
          shall perform its  responsibilities  under this  Agreement in a manner
          that  does  not   infringe,   or   constitute   an   infringement   or
          misappropriation  of, any  Intellectual  Property  Rights of any third
          party.

26.  USE OF TELECOMMUNICATIONS AND OTHER SERVICES

     26.1. Condition to Provision of Services.

          Telecommunications  Services or Other  Services  shall not be used for
          any unlawful purpose. More than ten percent (10%) of the transmissions

                                       43
<PAGE>

          will be interstate transmissions.  The parties represent to each other
          that this Agreement, to the extent it is subject to FCC regulation, is
          an inter-carrier  agreement not subject to the filing  requirements of
          Section 211 (a) of the  Communications  Act of 1934,  as amended.  One
          strand of the  Williams  Network is  contractually  limited to use for
          multimedia  transmission  (i.e.  internet  traffic,  video  and  radio
          transmission services and/or related applications, including, graphic,
          visual,  imaging,   interactive  and  multimedia  transmissions)  (the
          "Restricted Fiber"). If the parties want to use such Restricted Fiber,
          upon request from Williams,  WinStar agrees within a reasonable period
          of time to  identify  the  nature  of its  proposed  use of the  Other
          Service  so as to  permit  Williams  to  determine  whether  the Other
          Service  may be  carried  over the  Restricted  Fiber.  The fact  that
          Williams may not utilize the Restricted  Fiber for such  transmissions
          shall not affect  Williams'  obligation to provide  Telecommunications
          Services or Other Services unless otherwise  specifically set forth in
          this Agreement.

     26.2. Intrastate Interexchange Services.

          WinStar  may  use  any  interexchange   service  provided  under  this
          Agreement  including  any  service  provided  by means  of a  Backbone
          Agreement  only if such  interexchange  service  is used for  carrying
          inter-state  (as  defined  by  the  FCC)   telecommunications   (i.e.,
          telecommunications   subject  to  the   jurisdiction  of  the  Federal
          Communications  Commission).  Williams and its Affiliates shall not be
          obligated to make available  Telecommunications  Services,  Additional
          Services,  or other interexchange service on a Circuit with end points
          within   a   single   state   or   service   on   a   Circuit    which
          originates/terminates  at points both of which are  situated  within a
          single  state  unless   WinStar   represents   in  writing  that  such
          interexchange  service or Circuits shall be used to carry  inter-state
          telecommunications (as defined by the FCC).

     26.3. WinStar Responsibilities.

          WinStar  has  sole   responsibility  for  installation,   testing  and
          operation of facilities, services and equipment ("WinStar Facilities")
          other than those  specifically  provided  by  Williams  as part of the
          Telecommunications  Services  or  Other  Services  as  described  in a
          Service  Order.  In  no  event  will  the  untimely   installation  or
          non-operation of WinStar  Facilities relieve WinStar of its obligation
          to pay charges for the Service or Other  Service  after the  Requested
          Start Date as set forth in the Service Order.

     26.4. Consents.

          As  between  the  parties,   WinStar  shall  be  responsible  for  all
          arrangements with copyright  holders,  music licensing  organizations,
          performers'   representatives   or   other   parties   for   necessary
          authorizations,  clearances or consents  with respect to  transmission
          contents.

                                       44
<PAGE>

     26.5. Restriction of Transmissions.

          WinStar  will not  transmit  content,  nor  permit  its  customers  to
          transmit   content  that  violates   applicable   law  or  carries  an
          unreasonable  risk of leading  to  criminal,  civil or  administrative
          proceedings or investigations against Williams or WinStar.
         
     26.6 Compliance with Regulations.

          If the FCC,  any state  regulatory  body,  or any court,  in each case
          having competent  jurisdiction,  determines that any provision of this
          Agreement  violates any applicable  rules,  policies,  or regulations,
          both parties  shall  reasonably  cooperate to  immediately  bring this
          Agreement  into  compliance,   consistent  with  the  intent  of  this
          Agreement.

     26.6. Reasonableness, Consents and Approval.

          (a)  Where this  Agreement  requires  a party to assist or  cooperate,
               such requirement  shall not be interpreted to require  materially
               more than a  commercially  reasonable  level of effort (i.e.  the
               standard applicable will not be "best efforts" or "exhausting all
               available means").

          (b)  Except where  expressly  provided as being in the sole discretion
               of a party, where agreement,  approval,  acceptance,  consent, or
               similar action by either party is required under this  Agreement,
               such action shall not be  unreasonably  delayed or  withheld.  An
               approval or consent given by a party under this  Agreement  shall
               not  relieve the other party from  responsibility  for  complying
               with  the  requirements  of  this  Agreement,  nor  shall  it  be
               construed as a waiver of any rights under this Agreement,  except
               as  and  to the  extent  otherwise  expressly  provided  in  such
               approval or consent.


                                       45

<PAGE>



         IN WITNESS  WHEREOF and in  confirmation  of their consent to the terms
and  conditions  contained in this  Agreement  and intending to be legally bound
hereby,  Williams and WinStar have executed and delivered  this  Agreement as of
the dates set forth below.

<TABLE>

<S>                                                            <C> 
WINSTAR WIRELESS, INC.                                          WILLIAMS COMMUNICATIONS, INC.



               /s/ Timothy R. Graham                                            /s/ Frank Semple
By:           --------------------------------------------      By:            ----------------------------------------
               Timothy R. Graham                                                Frank Semple
Name:         --------------------------------------------      Name:          ----------------------------------------
               Vice President                                                   President, Williams Network
Title         --------------------------------------------      Title:         ----------------------------------------
               December 17, 1998                                                December 17, 1998
Date:         --------------------------------------------      Date:          ----------------------------------------

</TABLE>

                                       46


<PAGE>

                                                                       EXHIBIT A
                                WILLIAMS SYSTEM
                               PART 1 -- ROUTE MAP
                                SYSTEMS SEGMENTS



                     MAP SHOWING PROPOSED WILLIAMS NETWORK
<PAGE>
                                                                       EXHIBIT A
                            PART 2 - SYSTEMS SEGMENTS
<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------------
                                        Planned     Estimated Number  Total
                               Fiber  Construction     Route    of    Fiber           Option       Percentage of
   System Segment              Type      Date          Miles  Fibers  Payment         Price        Route Miles
- ------------------------------------------------------------------------------------------------------------------------
<S>                            <C>      <C>          <C>       <C>   <C>           <C>              <C>     
Atlanta       Washington, DC   SMF-LS    12/31/98     827       4     $24,229,931   $ 4,135,000
Dallas        Houston          SMF-LS    12/31/98     250       4     $ 7,324,647   $ 1,250,000
Minneapolis   Kansas City      LEAF      12/31/98     445       4     $13,037,871   $ 1,112,500
- ------------------------------------------------------------------------------------------------------------------------
          January 1999 Delivery                     1,522             $44,592,449   $ 6,497,600        10.37%
- ------------------------------------------------------------------------------------------------------------------------
Las Vegas     Los Angeles      LEAF      03/31/99     386       4     $11,309,255   $ 2,161,600
Atlanta       Jacksonville     LEAF      03/31/99     346       4     $10,137,311   $   865,000
Jacksonville  Miami            SMF-28    03/31/99     332       4     $ 9,727,131   $   830,000
Daytona       Tampa            LEAF      03/31/99     159       4     $ 4,658,475   $   397,500
- ------------------------------------------------------------------------------------------------------------------------
           March 1999 Delivery                      1,223             $35,832,172   $ 4,264,100          8.33%
- ------------------------------------------------------------------------------------------------------------------------
Houston       Atlanta          LEAF      06/30/99     993       4     $29,093,497   $ 2,482,500
Kansas City   Denver           LEAF      06/30/99     610       4     $17,872,138   $ 1,525,000
- ------------------------------------------------------------------------------------------------------------------------
            June 1999 Delivery                      1,603             $46,965,636   $ 4,007,500         10.92%
- ------------------------------------------------------------------------------------------------------------------------
Miami         Tallahassee      LEAF      09/30/99     580        4    $16,993,180   $ 1,450,000
- ------------------------------------------------------------------------------------------------------------------------
         September 1999 Delivery                      580             $16,993,180   $ 1,450,000          3.95%
- ------------------------------------------------------------------------------------------------------------------------
Tallahassee    New Orleans     LEAF      12/31/99     400        4    $11,719,435   $ 1,000,000
Denver         Salt Lake City  LEAF      12/31/99     397        4    $11,631,539   $   992,500
Los Angeles    San Diego       LEAF      12/31/99     165        4    $ 4,834,267   $   412,500
San Diego      Phoenix         LEAF      12/31/99     375        4    $10,986,970   $   937,500
Cleveland      New York        LEAF      12/31/99     760        4    $22,266,926   $ 1,900,000
- ------------------------------------------------------------------------------------------------------------------------
          December 1999 Delivery                    2,097             $61,439,137   $ 5,242,500         14.23%
- ------------------------------------------------------------------------------------------------------------------------
Salt Lake City Sacramento      LEAF      09/30/00     656        4    $19,219,873   $ 1,640,000
Sacramento     Oakland         LEAF      09/30/00      43        4    $ 1,259,839   $   107,500
Oakland        San Fransico    LEAF      09/30/00      70        4    $ 2,050,901   $   175,000
Oakland        Modesto         LEAF      09/30/00     127        4    $ 3,720,921   $   317,500
- ------------------------------------------------------------------------------------------------------------------------
         September 1999 Delivery                      896             $26,251,534   $ 2,224,000          6.10%
- ------------------------------------------------------------------------------------------------------------------------
Seattle        Portland        LEAF      12/31/00     200        4    $ 5,859,717   $   500,000
Portland       Sacramento      LEAF      12/31/00     700        4    $20,509,011   $ 3,500,000
Sacramento     Los Angeles     LEAF      12/31/00     470        4    $13,770,336   $ 2,350,000
New York       Boston          LEAF      12/31/00     250        4    $ 7,324,647   $   625,000
- ------------------------------------------------------------------------------------------------------------------------
          December 2000 Delivery                    1,620             $47,463,711   $ 6,975,000          11.03%
- ------------------------------------------------------------------------------------------------------------------------
Boston         Albany          LEAF      06/30/01     180        4    $ 5,273,746   $   450,000
- ------------------------------------------------------------------------------------------------------------------------
            June 2001 Delivery                        180             $ 5,273,746   $   450,000            1.23%
- ------------------------------------------------------------------------------------------------------------------------
Minneapolis    Cleveland       LEAF      09/30/01   1,124        4    $32,931,612   $ 5,620,000
Dallas         Kansas City     LEAF      09/30/01     661        4    $19,366,366   $ 3,305,000
Cleveland      Washington, DC  LEAF      09/30/01     400        4    $11,719,435   $ 1,000,000
Atlanta        Nashville       LEAF      09/30/01     220        4    $ 6,445,689   $   550,000
Nashville      Chicago         LEAF      09/30/01     630        4    $18,458,110   $ 1,575,000
- ------------------------------------------------------------------------------------------------------------------------
         September 2001 Delivery                    3,035             $88,921,211   $12,050,000           20.67%
- ------------------------------------------------------------------------------------------------------------------------
Kansas City    Chicago         LEAF      12/31/01     389        4    $11,397,150   $   972,500
Phoenix        Houston         LEAF      12/31/01   1,539        4    $45,090,525   $ 7,695,000
- ------------------------------------------------------------------------------------------------------------------------
          December 2001 Delivery                    1,928             $56,487,676   $ 8,667,500           13.13%
========================================================================================================================
      Totals                                       14,684            $430,220,451   $51,834,100          100.00%
========================================================================================================================
</TABLE>
============================================================================
 WinStar Payment for 4 Dark Fibers, Collocation, 
    and Maintenance Charges                            $ 430,220,451
 WinStar Option Price for 2 Additional Dark Fibers 
    (no charge for Collocation and Maintenance)        $  51,834,100
============================================================================

<PAGE>

                                                                       Exhibit B

                        Williams Network Pricing Schedule

This Pricing Schedule is made as of this _____ day of ________________, 199__,
and is subject to that Carrier Services Agreement No. __________________ (the
"CSA") by and between Williams Communications, Inc. d/b/a Williams Network, a
Delaware corporation ("Williams"), and
____________________________________________, a _____________________
corporation ("WinStar").

I.       ATM  SERVICES

1.        Rates & Charges: Williams Network ATM service has three basic rate
          elements; Access, Port Connections, and either Committed Bit Rate
          (CBR), or Variable Bit Rate (VBR) Permanent Virtual Circuits (PVCs)
          and Virtual Paths (VPs).

          1.1 Permanent virtual circuit (PVC) and Virtual Path (VP) bandwidth
          charges. PVC and VP charges are based on the class of service (CoS)
          and bandwidth selected. Bandwidth charges are stated in Committed
          Information Rates (CIR) or Megabit per second (Mbps) increments for
          one-way, or Simplex PVCs. CIR increments are available in 1Meg
          increments up to 40Mbps for DS3 ports, 5 Meg increments up to 150 Mpbs
          for OC3 ports and 25 Meg increments up to 600 Mbps for OC12 ports. Two
          Classes of Service are offered; Constant Bit Rate (CBR) and Variable
          Bit Ratenon non real time (VBRnrt). Port charges are based on port
          speed connections selected. Options currently are DS3, OC3 and OC12.
          Monthly recurring charges for port, PVCs and VPs are as follows:

<TABLE>
<CAPTION>
- -------------------------------------------------------------------------------------------
                                Monthly Recurring Charges
       Port            CIR (Mbps)           Port              CoS          Price Per Meg
- ------------------- ----------------- ----------------- ----------------- -----------------
<S>    <C>              <C>              <C>                <C>               <C> 
       DS3                1-9              $4,500            VBRnrt             $151
- ------------------- ----------------- ----------------- ----------------- -----------------
                         10-19             $4,500            VBRnrt             $147
- ------------------- ----------------- ----------------- ----------------- -----------------
                         20-29             $4,500            VBRnrt             $144
- ------------------- ----------------- ----------------- ----------------- -----------------
                         30-40             $4,500            VBRnrt             $140
- ------------------- ----------------- ----------------- ----------------- -----------------
       OC3                5-20             $11000            VBRnrt             $147
- ------------------- ----------------- ----------------- ----------------- -----------------
                         25-35             $11000            VBRnrt             $144
- ------------------- ----------------- ----------------- ----------------- -----------------
                         40-55             $11000            VBRnrt             $140
- ------------------- ----------------- ----------------- ----------------- -----------------
                         60-75             $11000            VBRnrt             $137
- ------------------- ----------------- ----------------- ----------------- -----------------
                         80-95             $11000            VBRnrt             $133
- ------------------- ----------------- ----------------- ----------------- -----------------
                        100-120            $11000            VBRnrt             $130
- ------------------- ----------------- ----------------- ----------------- -----------------
                        125-150            $11000            VBRnrt             $126
- ------------------- ----------------- ----------------- ----------------- -----------------
       OC12              25-75            $37,000            VBRnrt             $133
- ------------------- ----------------- ----------------- ----------------- -----------------
                        100-175           $37,000            VBRnrt             $130
- ------------------- ----------------- ----------------- ----------------- -----------------
                        200-275           $37,000            VBRnrt             $126
- ------------------- ----------------- ----------------- ----------------- -----------------
</TABLE>

<PAGE>
<TABLE>
<CAPTION>
- -------------------------------------------------------------------------------------------
                                Monthly Recurring Charges
       Port            CIR (Mbps)           Port              CoS          Price Per Meg
- ------------------- ----------------- ----------------- ----------------- -----------------
<S>    <C>              <C>              <C>                <C>               <C> 
                        300-350           $37,000            VBRnrt             $123
- ------------------- ----------------- ----------------- ----------------- -----------------
                        375-475           $37,000            VBRnrt             $119
- ------------------- ----------------- ----------------- ----------------- -----------------
                        500-600           $37,000            VBRnrt             $116
- ------------------- ----------------- ----------------- ----------------- -----------------
       DS3                1-9              $4,500             CBR               $323
- ------------------- ----------------- ----------------- ----------------- -----------------
                         10-19             $4,500             CBR               $315
- ------------------- ----------------- ----------------- ----------------- -----------------
                         20-29             $4,500             CBR               $308
- ------------------- ----------------- ----------------- ----------------- -----------------
                         30-40             $4,500             CBR               $300
- ------------------- ----------------- ----------------- ----------------- -----------------
       OC3                5-20             $11000             CBR               $315
- ------------------- ----------------- ----------------- ----------------- -----------------
                         25-35             $11000             CBR               $308
- ------------------- ----------------- ----------------- ----------------- -----------------
                         40-55             $11000             CBR               $300
- ------------------- ----------------- ----------------- ----------------- -----------------
                         60-75             $11000             CBR               $293
- ------------------- ----------------- ----------------- ----------------- -----------------
                         80-95             $11000             CBR               $285
- ------------------- ----------------- ----------------- ----------------- -----------------
                        100-120            $11000             CBR               $278
- ------------------- ----------------- ----------------- ----------------- -----------------
                        125-150            $11000             CBR               $270
- ------------------- ----------------- ----------------- ----------------- -----------------
       OC12              25-75            $37,000             CBR               $285
- ------------------- ----------------- ----------------- ----------------- -----------------
                        100-175           $37,000             CBR               $278
- ------------------- ----------------- ----------------- ----------------- -----------------
                        200-275           $37,000             CBR               $270
- ------------------- ----------------- ----------------- ----------------- -----------------
                        300-350           $37,000             CBR               $263
- ------------------- ----------------- ----------------- ----------------- -----------------
                        375-475           $37,000             CBR               $255
- ------------------- ----------------- ----------------- ----------------- -----------------
                        500-600           $37,000             CBR               $248
- ------------------- ----------------- ----------------- ----------------- -----------------
</TABLE>


2.1      Non-recurring Charges:

         Non-recurring charges include installation, configuration changes,
         order cancellations and order changes that may be incurred for the Port
         or PVC.

                                       2
<PAGE>



- ---------------------------------------------------------------------------
                               Non Recurring Charges
             Description of Charge                            Charges
- --------------------------------------- -----------------------------------
Installation:
- --------------------------------------- -----------------------------------
45Mb Port                                        $1,500
- --------------------------------------- -----------------------------------
155Mb Port                                       $4,000
- --------------------------------------- -----------------------------------
622Mb Port                                       $15,000
- --------------------------------------- -----------------------------------
per PVC                                          $40
- --------------------------------------- -----------------------------------

- --------------------------------------- -----------------------------------
Ancillary Charges:
- --------------------------------------- -----------------------------------
Configuration Changes                            $50
- --------------------------------------- -----------------------------------
Order Cancellation                               $250
- --------------------------------------- -----------------------------------
PVC Order Change                                 $50
- --------------------------------------- -----------------------------------
Port Order Change                                $100
- --------------------------------------- -----------------------------------

          Configuration change charges are applied when the parameters of
          Virtual Channels (VCs) are changed. Order Cancellation Charges apply
          when a PVC or Port has been ordered and needs to be canceled prior to
          the Service having been installed and accepted.

          PVC Order Change Charges apply when WinStar requests a change to the
          PVC.

          Port Order Change Charges apply when WinStar requests to change the
          port size ordered. If the Port has been installed and accepted,
          WinStar will be charged for a new port installation.

3.1       ATM Discount Structure

          Contributing Williams Network ATM Service charges include recurring
          port and PVC charges only. Contributing charges do not include any
          credits to which WinStar may be entitled, late payment penalties,
          taxes or other government surcharges, any one-time non-recurring fees
          and charges or any charges related to Local Access Services. The
          discount structure is based on the monthly revenue achieved by WinStar
          (contributing charges) and the stated length of the Service Order
          established. The discount WinStar will receive in any given month will
          be determined by the level of revenue achieved by WinStar for that
          month. WinStar will receive the stated discounts off of Williams?
          standard rates as such rates may exist from time to time.

                                       3
<PAGE>


<TABLE>
<CAPTION>

- -------------------------------------------------------------------------------------------
                                    Discount Structure
Monthly Revenue     1 Year         2 Year         3 Year         4 Year         5 Year
- ---------------- -------------- -------------- -------------- -------------- --------------
<S>   <C>             <C>            <C>            <C>            <C>            <C>
      $0              0%             0%             0%             0%             0%
- ---------------- -------------- -------------- -------------- -------------- --------------
    $25,000           12%            14%            18%            22%            27%
- ---------------- -------------- -------------- -------------- -------------- --------------
    $50,000           14%            16%            20%            24%            29%
- ---------------- -------------- -------------- -------------- -------------- --------------
   $100,000           16%            18%            22%            26%            31%
- ---------------- -------------- -------------- -------------- -------------- --------------
   $150,000           18%            20%            24%            28%            33%
- ---------------- -------------- -------------- -------------- -------------- --------------
   $200,000           20%            22%            26%            30%            35%
- ---------------- -------------- -------------- -------------- -------------- --------------
</TABLE>

         Private Line Services

1.       Williams Network Private Line Service has three basic rate elements;
         IXC charges, Local Access Charges and Non-recurring charges.

         1.1      IXC rates are determined on an individual case basis and will
                  be set forth on WinStar's Service Order. The minimum monthly
                  charge for any IXC circuit ordered by WinStar shall be as
                  follows:

          ---------------------------------------------------------
                          Minimum Monthly Charges
          ---------------------------------------------------------
          DS-3                               $2,000
          ---------------------------------- ----------------------
          OC-3                               $5,000
          ---------------------------------- ----------------------
          OC-12                              $20,000
          ---------------------------------- ----------------------
          OC-48                              $80,000
          ---------------------------------- ----------------------


                                       4
<PAGE>


Non-recurring Charges:
<TABLE>
<CAPTION>
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
             Non-Recurring Charges                    DS-1             DS-3           OC-3           OC-12          OC-48
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
<S>                                                   <C>             <C>            <C>            <C>            <C>    
New Order Installation                                $400            $2,000         $5,000         $18,000        $48,000
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
Order Change (1st change free)                         $25             $50           $2,000         $3,000          $4,000
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
Order Cancellation (prior to activation)              $150             $250          $2,000         $3,000          $4,000
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
 ASR (new or disconnect) Special Access               $250             $250           $250           $250            $250
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
ASR Supplement                                        $150             $150           $150           $150            $150
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
Order Expedite                                        $300             $300           $300           $300            $300
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
Reconfiguration                                       $500            $2,000         $6,000         $12,000        $24,000
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
Additional Installation/Maintenance/Engineering    $100.00/hr       $100.00/hr     $100.00/hr     $100.00/hr      $100.00/hr
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
After Hours                                      $150.00/hr       $150.00/hr      $150.00/hr     $150.00/hr     $150.00/hr
- ------------------------------------------------ ---------------- --------------- -------------- -------------- ---------------
</TABLE>

<TABLE>
<CAPTION>
- ------------------------------------------------ ------------------------------------- ----------------------------------------
             Cross-Connect Charge                         Monthly Recurring                         Non-Recurring
- ------------------------------------------------ ------------------------------------- ----------------------------------------
<S>                     <C>                                      <C>                                    <C> 
                     DS-3                                        $250                                   $500
- ------------------------------------------------ ------------------------------------- ----------------------------------------
                     OC-3                                        $800                                  $1,000
- ------------------------------------------------ ------------------------------------- ----------------------------------------
                     OC-12                                      $3,250                                 $10,000
- ------------------------------------------------ ------------------------------------- ----------------------------------------
                     OC-48                                     $12,000                                 $25,000
- ------------------------------------------------ ------------------------------------- ----------------------------------------
</TABLE>

         Installation charges shall apply to the normal installation of
         equipment necessary to provide the requested service to the point of
         demarcation at WinStar's premises. Additional Installation charges
         shall apply when Williams is required to install equipment other than
         that normally required to provide the service or when WinStar requests
         special equipment.

3.1      Private Line Discount Structure

         Contributing Williams Network Private Line Service charges include
         monthly recurring IXC charges only. Contributing charges do not include
         any credits to which WinStar may be entitled, late payment penalties,
         taxes or other government surcharges, any one-time non-recurring fees
         and charges or any charges related to Local Access Services. The
         discount structure is based on the monthly revenue achieved by WinStar
         (contributing charges) and the stated length of the Service Order
         established. The discount WinStar will receive in any given month will
         be determined by the level of revenue achieved by WinStar for that
         month. WinStar will receive the stated discounts off of Williams'
         standard rates as such rates may exist from time to time.

          ------------------------------------------------------------
                        Rates per VG&E V&H mile On Net.
          ------------------------------------------------------------
                       DS-3                         $ 0.0230
          -------------------------------- ---------------------------
                       OC-3                         $0.0220
          -------------------------------- ---------------------------
                       OC-12                        $0.0185
          -------------------------------- ---------------------------
                       OC-48                        $0.0165
          -------------------------------- ---------------------------

                                       5

<PAGE>

III.     Frame Relay Services

1.       Rates & Charges: Williams Network Frame Relay Service has four
         principle rate elements: Access, Port Connections, Permanent Virtual
         Circuits (PVCs), and Flex-CIR (Time-of-Day and/or Day-of-Week)
         configuration charges.

         Ports and PVCs are further categorized as being either a
         User-to-Network Interface (UNI) type or Network-to-Network Interface
         (NNI) type. An NNI port is defined as one end of a connection between
         Williams' frame relay network and another carrier's network. The
         connecting carrier could be either a customer or off-net service
         provider. Similarly, an NNI PVC is defined as one which has each end of
         the PVC residing in two different carrier's frame relay networks,
         rather than the originating and terminating points being in the same
         carrier's network.

1.1      Port Charges: Both UNI and NNI port charges are based solely on the
         bandwidth selected by WinStar. Available port speeds range from 64
         Kilobits per second (Kbps) to 1.536 Megabits per second (Mbps). See
         rate table below for list of available speeds. Monthly recurring and
         non-recurring charges for frame relay ports are provided in the rate
         table below.

1.1.2    Permanent Virtual Circuit (PVC) bandwidth charges: UNI and NNI PVC
         charges are both based solely on the bandwidth selected by WinStar.
         Bandwidth charges are stated in Committed Information Rates (CIR) or
         Kbps increments for one-way, or Simplex PVCs. Available PVC-CIR speeds
         range from 4 Kbps to 1.024 Mbps. See rate table below for list of
         available speeds. Monthly recurring and non-recurring charges for frame
         relay PVCs are provided in the rate table below.

                                       6

<PAGE>

1.1.3    Frame Relay Rate Table

<TABLE>
<CAPTION>
- ------------------------------- ---------------- ------------------- -------------------
Frame Relay Service Components     Speed/CIR
                                    (Kbps)            MRC ($)         Installation ($)
- ------------------------------- ---------------- ------------------- -------------------
<S>                                        <C>     <C>                 <C>       
NNI Port (Private NNI)                       64    $      224          $      250
                                            128    $      418          $      250
(Add: "NNITrunking Charge")                 192    $      455          $      250
Charge")
                                            256    $      492          $      250
                                            320    $      610          $      250
                                            384    $      727          $      250
                                            448    $      823          $      250
                                            512    $      920          $      250
                                            576    $      984          $      250
                                            640    $      1,049        $      250
                                            704    $      1,114        $      250
                                            768    $      1,179        $      250
                                           1024    $      1,471        $      250
                                           1536    $      1,856        $      250
NNIPVC                                        0    $      8            $      25
                                              4    $      8            $      25
(SimplexPricing)                              8    $      10           $      25
                                             16    $      12           $      25
                                             32    $      20           $      25
                                             48    $      30           $      25
                                             64    $      40           $      25
                                            128    $      80           $      25
                                            192    $      119          $      25
                                            256    $      159          $      25
                                            320    $      199          $      25
                                            384    $      239          $      25
                                            448    $      278          $      25
                                            512    $      318          $      25
                                            576    $      358          $      25
                                            640    $      398          $      25
                                            704    $      437          $      25
                                            768    $      477          $      25
                                            832    $      517          $      25
                                            896    $      557          $      25
                                            960    $      596          $      25
                                           1024    $      636          $      25
UNIPorts                                     64    $      224          $      250
                                            128    $      418          $      250
                                            192    $      455          $      250
                                            256    $      492          $      250

                                            320    $      610          $      250
                                            384    $      727          $      250
                                            448    $      823          $      250
                                            512    $      920          $      250
                                            576    $      984          $      250
</TABLE>

                                       7
<PAGE>
<TABLE>
<CAPTION>
- ------------------------------- ---------------- ------------------- -------------------
Frame Relay Service Components     Speed/CIR
                                    (Kbps)            MRC ($)         Installation ($)
- ------------------------------- ---------------- ------------------- -------------------
<S>                                        <C>     <C>                 <C>       
                                            640    $      1,049        $      250
                                            704    $      1,114        $      250
                                            768    $      1,179        $      250
                                           1024    $      1,471        $      250
                                           1536    $      1,856        $      250
UNIPVCs                                       0    $      8            $      25
                                              4    $      8            $      25
(SimplexPricing)                              8    $      10           $      25
                                             16    $      12           $      25
                                             32    $      20           $      25
                                             48    $      30           $      25
                                             64    $      40           $      25
                                            128    $      80           $      25
                                            192    $      119          $      25
                                            256    $      159          $      25
                                            320    $      199          $      25
                                            384    $      239          $      25
                                            448    $      278          $      25
                                            512    $      318          $      25
                                            576    $      358          $      25
                                            640    $      398          $      25
                                            704    $      437          $      25
                                            768    $      477          $      25
                                            832    $      517          $      25
                                            896    $      557          $      25
                                            960    $      596          $      25
                                           1024    $      636          $      25
Local Access                    DS-0/DDS           ICB                 ICB
                                                   ICB

                                FT-1               ICB                 ICB
                                                   ICB

                                DS-1               ICB                 ICB

NNI Trunking Charge             DS-0/DDS           ICB                 ICB
                                                   ICB

                                FT-1               ICB                 ICB
                                                   ICB

                                DS-1               ICB                 ICB
- ------------------------------- ---------------- ------------------- -------------------
</TABLE>

                                       8


<PAGE>   

1.2  Enhanced Services: The basic Frame Relay Service components described in
     the previous sections can be bundled and molded into a wide variety of
     different service offerings. The following descriptions outline how
     Williams packages these service components to address the specialized
     requirements of its wholesale customers.




1.2.1 Frame Relay/ATM Service Interworking:

<TABLE>
<CAPTION>
- ------------------------------------- ------------------------ -------------------------------
Enhanced Wholesale Services           Installation             MRC
- ------------------------------------- ------------------------ -------------------------------
<S>                                   <C>                      <C>
Frame Relay/ATM Interworking          (No additional charge    (No additional charge for
                                       --------------------     --------------------    
                                      for locations            locations requiring ATM
                                      requiring ATM beyond     beyond that for standard ATM
                                      that for standard ATM    service)
                                      service)
- ------------------------------------- ------------------------ -------------------------------
</TABLE>

1.3  Flex-CIR Services: Williams Flex-CIR Service is designed to help end-users
     in two ways:

     1.   Reserve the exact amount of bandwidth needed by the end-user during
          the hours it is most critical.

     2.   Minimize the end-user's network costs by "turning off" excess
          bandwidth during the hours when it is least required.

         Specifically, WinStar will be able to adjust its PVC speeds (or CIR) at
         quarter-hour increments (e.g. 8:00, 8:15, 8:30, 8:45, etc.). Once
         WinStar has made a speed change, WinStar will not be able to make
         another change for at least two (2) hours. WinStar shall have the
         option of establishing different speed schedules for the same PVC
         depending on the day of the week (e.g. turning a Flex-CIR PVC down from
         its "weekday speed" of 256 Kbps CIR to 64 Kbps CIR on the weekend). The
         configuration charges for this enhanced service are provided in the
         table below

                                       8
<PAGE>

1.3.1
<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------------
                          Time-of-Day/Day-of-Week Flex-CIR
                                     PVC Charges
         Description                 NRC (Per PVC)              MRC (Per PVC)
- ------------------------------- ------------------------ -----------------------------
<S>                             <C>                      <C>
Basic PVC Charge                (Standard NRC charge     (Standard MRC charge for
(Based on weighted average of   for average CIR level)   average CIR level)
CIRs)
- ------------------------------- ------------------------ -----------------------------
TOD Configuration Charge (2     $40                      $60
CIR adjustments per day)
- ------------------------------- ------------------------ -----------------------------
DOW Configuration Charge (2     $40                      $60
CIR adjustments per wk.)
- ------------------------------- ------------------------ -----------------------------
Each additional CIR             $20                      $30
adjustment per period (Per
day or per week)
- ------------------------------- ------------------------ -----------------------------
</TABLE>

2.1      Additional Non-recurring Charges: In addition to the non-recurring
         charges set forth in the tables above, WinStar may incur the following
         additional non-recurring charges.

<TABLE>
<CAPTION>
- ----------------------------------------------------------------------------------
                        Additional Non-Recurring Charges
          Description of Charge                            Charge
- ------------------------------------------ ---------------------------------------
<S>                                        <C>
Basic PVC Reconfiguration Changes          $50
- ------------------------------------------ ---------------------------------------
Flex-CIR PVC Reconfiguration Changes       Apply Standard Installation Charges
- ------------------------------------------ ---------------------------------------
PVC Order Cancellation Charge              $40
- ------------------------------------------ ---------------------------------------
Port Order Change Charge                   $100
- ------------------------------------------ ---------------------------------------
Port Order Cancellation Charge             $250
- ------------------------------------------ ---------------------------------------
</TABLE>

          Configuration charges are applied when the parameters of PVCs are
          changed. PVC Order Cancellation Charges apply when WinStar cancels a
          PVC order prior to its installation.

          Port Order Change Charges apply when WinStar requests to change the
          port size ordered. If the Port has been installed and accepted,
          WinStar will be charged for a new port installation.

          Port Cancellation Charges apply when WinStar cancels a port order
          prior to installation.

                                       10
<PAGE>


3.1      Frame Relay Discount Schedule

         Contributing Williams Network Frame Relay Service charges include
         monthly recurring charges only. Contributing charges do not include any
         credits to which WinStar may be entitled, late payment penalties, taxes
         or other government surcharges, any one-time non-recurring fees and
         charges or any charges related to Local Access Services. The discount
         structure is based on the monthly revenue achieved by WinStar
         (contributing charges) and the stated length of the Service Order
         established. The discount WinStar will receive in any given month will
         be determined by the level of revenue achieved by WinStar for that
         month. WinStar will receive the stated discounts off of Williams'
         standard rates as such rates may exist from time to time.

<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------------
                            Frame Relay Discount Schedule

Monthly Revenue                 1 Year     2 Year     3 Year     4 Year      5 Year
- ----------------------------- ----------- ---------- ---------- ---------- -----------
<S>                           <C>         <C>        <C>        <C>        <C>
$0                            0%          0%         0%         0%         0%
- ----------------------------- ----------- ---------- ---------- ---------- -----------
$25,000                       12%         14%        18%        22%        27%
- ----------------------------- ----------- ---------- ---------- ---------- -----------
$50,000                       14%         16%        20%        24%        29%
- ----------------------------- ----------- ---------- ---------- ---------- -----------
$100,000                      16%         18%        22%        26%        31%
- ----------------------------- ----------- ---------- ---------- ---------- -----------
$150,000                      18%         20%        24%        28%        33%
- ----------------------------- ----------- ---------- ---------- ---------- -----------
$200,000                      20%         22%        26%        30%        35%
- ----------------------------- ----------- ---------- ---------- ---------- -----------
</TABLE>


IV.      Pricing General Conditions

1.       All pricing set forth in Sections I, II and III above is Williams'
         current pricing. Such pricing is subject to change upon thirty (30)
         days written notice by Williams to WinStar. Price changes shall only be
         effective on a going-forward basis and shall not apply to Service
         Orders previously placed by WinStar and accepted by Williams.

                                       11
<PAGE>

                                                                       EXHIBIT B
                    Williams Network Technical Specifications

I.  Technical Specifications for ATM and Frame Relay Services

1.0      Williams Network Technical Specifications are stated as an objective
         that the ATM and Frame Relay Services will perform in accordance with
         prevailing telecommunications industry standards. All Service provided
         under Williams ATM and Frame Relay Services are measured using two
         variables: Network Availability and Mean-time-to-restore.

2.0      Quality Standards

         2.1      General. ATM and Frame Relay Service standards apply on a
                  one-way basis between the WinStar Premises Network Interface
                  Points ("CPNIP") which are connected to Local Access between
                  which ATM and Frame Relay Interexchange Service is provided
                  (CPNIP to CPNIP or End-to-End) and exclude nonperformance due
                  to force majeure or planned interruptions for necessary
                  maintenance purposes. The actual end-to-end availability and
                  performance of ATM and Frame Relay Service may be affected by
                  the WinStar provided equipment, dependent upon the type and
                  quality of WinStar equipment used. (WinStar provided Local
                  Access may not meet these specifications.)

         2.2      Availability. Availability is a measurement of the percent of
                  total time that service is operative when measured over a 365
                  consecutive day (8760 hour) period. The Local Access
                  availability standards for ATM and Frame Relay Services are
                  established by the Local Access Provider. For ATM and Frame
                  Relay Services on the Williams network, availability shall be
                  99.95% from point-of-presence ("POP") to POP measured over a
                  one year period. For Services not on the Williams network, the
                  off-net provider will establish availability.

3.0      Maintenance

         Repair efforts will be undertaken upon notification of trouble by
         internal network surveillance and network surveillance and performance
         systems or by notification of trouble and release of all or part of the
         ATM or Frame Relay Service by WinStar for testing.

                                       12
<PAGE>

4.0      Mean Time to Restore

         Mean Time to Restore (MTTR) is the average time required to restore
         service and resume availability and is stated in terms of equipment and
         cable outages. The time is measured from the moment the outage is
         reported until the service is available and applies specifically to
         equipment outages or failures.

          4.1     MTTR Objective:           2 Hours (Equipment)

                         6 Hours (First Fibers on Cable)

5.0      Calculation. Williams Network calculates network availability on
         WinStar action requests. WinStar must notify the Williams Network
         Customer Care department and initiate an action request to determine if
         Service variables stated above were met.

II.      Technical Specifications for Private Line Service

1.0      Interconnection Specifications

         1.1   DS-3. DS-3 service is provided in accordance with ANSI Standard
               T1.102 (formerly AT&T Compatibility Bulletin 119) and Technical
               Reference 54014 |_| 4. DS-3 Service operates at 44.736 Mbps.

         1.2   Optical SONET Services (OC-N). Optical SONET Services are
               provided in accordance with ANSI Standard T1.105. OC-3 Service
               operates at 155.520 Mbps and is configured with 3 separate STS-1
               signaling paths. OC-3C Service operates at 155.520 Mbps and is
               configured with 1 STS-3C signaling path (or 3 concatenated STS-1
               signaling paths). OC-12 Service operates at 622.080 Mbps with 12
               separate STS-1 signaling paths. OC-12C Service operates at
               622.080 Mbps with 1 STS-12C signaling path (or 4 separate STS-3C
               signaling paths). OC-48 Service operates at 9953.280 Mbps and is
               configured with 48 separate STS-1 signaling paths.

2.0      Quality Standards

         2.1      General. DS-3 and Optical SONET Service standards apply on a
                  one-way basis between WinStar Premises Network Interface
                  Points ("CPNIP") which are connected to Local Access between
                  which DS-3 and Optical SONET Interexchange Service is provided
                  (CPNIP to CPNIP or End-to-End) and exclude nonperformance due
                  to force majeure or planned interruptions for necessary
                  maintenance purposes. The actual end-to-end availability and
                  performance of DS-3 and Optical SONET Service may be affected
                  by WinStar provided equipment, dependent upon the type and
                  quality of WinStar equipment used. (WinStar provided Local
                  Access may not meet these specifications.)

                                       13
<PAGE>

         2.2      Availability. Availability is a measurement of the percent of
                  total time that service is operative when measured over a 365
                  consecutive day (8760 hour) period. DS-3 and Optical SONET
                  Service is considered inoperative when there has been a loss
                  of signal or when two consecutive 15 second loop-back tests
                  confirm the observation of any severely errored seconds or a
                  bit error rate equal to or worse than 1 x 10-3. The Local
                  Access availability standards for DS-3 and Optical SONET
                  Services are established by the Local Access Provider. For
                  Services on the Williams network, availability shall be 99.95%
                  from point-of-presence ("POP") to POP measured over a one year
                  period. For Services not on the Williams network, the off-net
                  provider will establish availability. For multi-media
                  services, availability will be the same as established by
                  WorldCom, Inc.

         2.3      Performance (% Error Free Seconds, while Available).
                  Performance is noted in Error Free Seconds (EFS) which are a
                  measure of the percentage of total seconds when measured over
                  a consecutive 24 hour period that do not contain bit errors.
                  Performance shall be measured on a one-way basis using a
                  Pseudo Random Bit Sequence test pattern as defined in CCITT
                  Recommendation 0.151. The Error Free Seconds standards for the
                  Local Access for DS-3 and Optical SONET Service is established
                  by the Local Access Provider. For Services on the Williams
                  network, Error Free Seconds shall be 99.5% from POP to POP
                  measured over a monthly period. For Services not on the
                  Williams network, the off-net provider will establish Error
                  Free Seconds. For multi-media services, Error Free Seconds
                  will be as defined by WorldCom, Inc.

3.0      Maintenance

         Repair efforts will be undertaken upon notification of trouble by
         internal network surveillance and network surveillance and performance
         systems or by notification of trouble and release of all or part of the
         DS-3 or Optical SONET Service by WinStar for testing.

4.0      Mean Time to Restore

         Mean Time to Restore (MTTR) is the average time required to restore
         service and resume availability and is stated in terms of equipment and
         cable outages. The time is measured from the moment the outage is
         reported until the service is available and applies specifically to
         equipment outages or failures.

         4.1     MTTR Objective:                     2 Hours (Equipment)

                         6 Hours (First Fibers on Cable)

5.0      Calculation. Williams Network calculates network availability on
         WinStar action requests. WinStar must notify the Williams Network
         Customer Care department and initiate an action request to determine if
         Service variables stated above were met.

                                       14
<PAGE>


                                                                       EXHIBIT C
                             COLLOCATION PROVISIONS
                                     PART 1

                   COLLOCATION PROVISIONS - TRANSMISSION SITES

         1.       Collocation Rights.

         a. Collocation. WinStar shall have the right to locate, install,
maintain and operate WinStar Equipment at Transmission Sites included in each
System Segment during the relevant IRU Term. Williams will provide to WinStar
either seventy-five (75) square feet or six (6) racks* at each Transmission Site
except with respect to the Dallas-Houston System Segment, where Williams shall
make commercially reasonable efforts to secure six (6) racks at each
Transmission Site. No use of Transmission Sites required or permitted under
these Collocation Provisions shall create or vest in WinStar any easements or
other ownership or property rights of any nature in Williams' real or personal
property. Williams shall construct and operate such space, and WinStar shall
cause the WinStar Equipment to be installed and operated, in accordance with
telecommunications industry standards for similar collocation arrangements.

         b. Basic Services. Williams shall designate each Transmission Site as
an optical amplifier site, a regenerator site, or a junction. At each
Transmission Site, Williams shall provide separate access, not located in its
backbone area, where available, space, HVAC, and DC power for the WinStar
Equipment as follows:

         Sites                                       Maximum Power 
         Optical Amplifier                           90 amps of 48v DC

         Regenerator                                    120 amps of 48v DC

         Junctions                                      180 amps of 48v DC

* A rack space adequate to contain a rack (measuring 26 inches (width) x 24
inches (depth) x 78 or 84 inches (height)). WinStar shall supply its own
cabinets.

The total linear inches for WinStar Rack Space within each Transmission Site
shall not exceed the sum of the number of Rack Spaces for the specified
Transmission Site multiplied by 26 inches. The services provided pursuant to
this Subsection shall be referred to as the "Basic Services."

         c. Charges for Basic Services. The Contract Price includes the charge
for Basic Services.


                                       16
<PAGE>



         d. Ancillary Collocation Services. WinStar may request in writing
installation services, AC power or additional DC power, additional back-up
power, technical assistance, additional space or racks, assistance in
establishing an Interconnection Facility (as defined below), or additional HVAC
(collectively referred to as the "Ancillary Collocation Services") at any
Transmission Site. Within fifteen (15) business days after receiving such
written request, Williams shall notify WinStar whether the Ancillary Collocation
Services are available and, if they are, Williams' standard rates for the
Ancillary Collocation Services. WinStar shall provide written notice to Williams
confirming its request for such Ancillary Collocation Services at the quoted
rates prior to Williams providing such Ancillary Collocation Services. If
upgrades or expansions to Transmission Sites or its facilities are necessary to
accommodate WinStar's request, Williams may include the entire cost of such
upgrades or expansions in the cost to WinStar.

         e. Charges for Ancillary Collocation Services. If WinStar chooses to
receive the Ancillary Collocation Services, WinStar shall pay any and all
(initial and continuing) costs reasonably incurred by Williams in providing such
Ancillary Collocation Services or Williams' standard prices for such Ancillary
Collocation Services at the relevant Transmission Site, provided that WinStar
has in either case agreed to such charges in advance in writing. WinStar shall
pay Williams the amounts due within thirty (30) days of receipt of an invoice
therefor from Williams. Following the fifth (5th) year after the Effective Date,
upon at least thirty (30) days' notice to WinStar, Williams may adjust recurring
charges for the Ancillary Collocation Services once each calendar year to equal
its then-current standard charges. Williams' current charges (as of the
Effective Date) for certain Ancillary Collocation Services are set forth in the
following tables:

<TABLE>
<CAPTION>
- ---------------------------------------------------- ------------------- ------------------ -----------------
Recurring Monthly Charges for Specific Minimum            One Year          Three Year      Five Year
Term Commitments                                            Term               Term               Term
- ---------------------------------------------------- ------------------- ------------------ -----------------
<S>                                                         <C>                <C>                <C> 
Rack                                                        $700               $650               $500
- ---------------------------------------------------- ------------------- ------------------ -----------------
Each AC amp                                                  0                   0                 0
- ---------------------------------------------------- ------------------- ------------------ -----------------
Each DC amp                                                  0                   0                 0
- ---------------------------------------------------- ------------------- ------------------ -----------------

- ---------------------------------------------------- ------------------- ------------------ -----------------
Nonrecurring Charges for Specific Minimum Term            One Year          Three Year      Five Year
Commitments (in addition to monthly charge)
- ---------------------------------------------------- ------------------- ------------------ -----------------
Rack                                                       $3,000             $1,500               0
- ---------------------------------------------------- ------------------- ------------------ -----------------
Each AC amp                                                 $75                 $75               $75
- ---------------------------------------------------- ------------------- ------------------ -----------------
Each DC amp                                                 $250               $250               $250
- ---------------------------------------------------- ------------------- ------------------ -----------------
</TABLE>

                                       18
<PAGE>
<TABLE>
<CAPTION>

- ---------------------------------------------------------------- ------------------------- ------------------------
                       Ancillary Charges                               Nonrecurring           Monthly Recurring
                                                                        Charge ($)               Charge ($)
- ---------------------------------------------------------------- ------------------------- ------------------------
<S>                                                                        <C>                        <C>
Change of Installation Date (pre-work date)                                100                        0
- ---------------------------------------------------------------- ------------------------- ------------------------
Service Order Change (pre-work date)                                       100                        0
- ---------------------------------------------------------------- ------------------------- ------------------------
Service Order Change (post-work date)                                      250                        0
- ---------------------------------------------------------------- ------------------------- ------------------------
Order Cancellation (more than 30 days before scheduled work                250                        0
date)
- ---------------------------------------------------------------- ------------------------- ------------------------
Order Cancellation (less than 30 days from scheduled work date)            500                        0
- ---------------------------------------------------------------- ------------------------- ------------------------
AC Power Addition (after initial installation)                             750                        0
- ---------------------------------------------------------------- ------------------------- ------------------------
Cross-Connect (per DS-3) (subject to limitations set forth in             1,000                      250
Section 2 of this Exhibit)
- ---------------------------------------------------------------- ------------------------- ------------------------
Early Termination (before one, three, or five year term                   100% of remaining contract term
expires)
- ---------------------------------------------------------------- --------------------------------------------------
</TABLE>



<TABLE>
<CAPTION>
- -------------------------------------------------------------------------------------------------------------------
                                            Dispatch Labor Charges ($)
- -------------------------------------------------------------------------------------------------------------------
<S>                                                                                    <C>         
Monday-Friday Business Hours                                                           100 per hour
- ------------------------------------------------------------------------ ------------------------------------------
Monday-Friday Non-Business Hours                                                       125 per hour
- ------------------------------------------------------------------------ ------------------------------------------
Saturday & Sunday                                                                      150 per hour
- ------------------------------------------------------------------------ ------------------------------------------
Holidays                                                                               150 per hour
- ------------------------------------------------------------------------ ------------------------------------------
</TABLE>

         f. Delivery and Installation. WinStar shall, at its expense, cause the
WinStar Equipment to be delivered, installed, and maintained in a safe condition
and meeting or exceeding the standards set forth in the Subsection entitled
Standards. Williams shall allow WinStar reasonable access to each Transmission
Site for purposes of installing WinStar Equipment beginning on or before the
Acceptance Date of the relevant System Segment, provided that, if a Transmission
Site is not ready for installation of equipment other than security, alarm,
HVAC, power, back-up power or other common systems on such date, Williams shall
allow such access within five (5) days of the first date such Transmission Site
is ready for such installation. Williams shall provide WinStar with at least
thirty (30) days notice prior to the date it estimates each Transmission Site
will be ready for installation of the WinStar Equipment.

         g. Interface. Interface points for the WinStar fibers shall be at fiber
patch panels or digital cross-connect (DSX-N) panels located in the Transmission
Sites. Such panels shall be the demarcation to establish each party's
operational and maintenance responsibilities. All cables placed to interface
such panels shall conform to all applicable Williams' standards.

                                       18
<PAGE>

         h. Alarms 24 x 7 Monitoring. Williams shall continuously monitor (i.e.,
24 x 7) Transmission Site security, environmental, and power alarms at one or
more manned monitoring centers. At WinStar's request, Williams shall establish
procedures to allow WinStar, at WinStar's expense, to share or receive alarm
information.

         i. Compliance with Agreement. Each party shall comply with the
provisions of the Agreement relating to Transmission Sites, including, without
limitation, Williams' obligations to provide as-built drawings of Transmission
Sites showing WinStar rack placement and assignment and to comply with the
Operations Specifications set forth in Exhibit I thereto.

         2.       Interconnections

         a. Right to Interconnect Off-Premises. WinStar shall have the right to
connect any of its premises to any Transmission Site (such connection or
entrance facility referred to herein as the "Interconnect Facility").
Transmission Sites are established and designed to support network transmission
equipment and, therefore, no interconnections may be made at such sites for
other purposes such as directly or indirectly connecting to local exchange
carrier facilities or other local access facilities or for purposes of providing
local exchange or local access services.

         b. Construction and Installation. WinStar shall provide at its expense
all necessary rights of way, permits, equipment and Williams-approved materials
to construct and install each Interconnect Facility, including, but not limited
to, cables and conduit and any labor charges associated therewith. Williams
shall reasonably cooperate with WinStar to facilitate reasonable WinStar
requests for Interconnection Facilities. Specifically, if necessary, and where
applicable, Williams shall assist WinStar at WinStar's expense, in obtaining
from any third-party building owner or Williams lessor access to existing
building entrance facilities, if available, to access and exit Transmission
Sites. The demarcation point for WinStar's facilities shall be in Williams'
fiber patch panel or the DSX-N panel in the Transmission Sites, as appropriate.

         c. Ownership. WinStar shall retain ownership of any portion of each
Interconnect Facility that is located on Transmission Sites during the IRU Term;
provided, however, that title to any part of the Interconnect Facility within a
Transmission Site shall be transferred to Williams upon expiration of the IRU
Term.

         d. Prohibition on Interconnection with Other Collocation Customers.
WinStar shall not establish interconnections between WinStar's collocated
facilities or the WinStar Equipment and the collocated facilities of other
parties who are using a Transmission Site. WinStar shall not use any
Interconnect Facility to allow third parties collocated in any Transmission Site
to interconnect with each other at that Transmission Site.

                                       19
<PAGE>

         e. Maintenance and Changes. WinStar shall provide all maintenance and
repair of the Interconnect Facility on WinStar's side of the point of
demarcation. Any improvement, modification, addition to, relocation, or removal
of, the Interconnect Facility by WinStar at Transmission Sites shall be subject 
to Williams' prior review and written approval. WinStar shall pay the cost of
such improvement, modification, addition to, relocation, or removal of, the
Interconnect Facility. Williams' approval will not be unreasonably withheld and
if Williams fails to respond to WinStar's written request within thirty (30)
days of receiving WinStar's request for such changes, Williams shall be deemed
to have approved WinStar's request. Williams' maintenance responsibility shall
be limited to the demarcation point and the associated cross connect at that
point.

         3. Notice to Interconnect or Collocate. No later than sixty (60) days
prior to WinStar's planned installation of its WinStar Equipment or Interconnect
Facilities at any Transmission Site, WinStar shall provide to Williams the
"Interconnect/Collocation Notice." The Interconnect/Collocation Notice shall
include notice of WinStar's desire to interconnect/collocate in a particular
Transmission Site, a copy of WinStar's construction design drawings and
installation schedule. The Interconnect/Collocation Notice shall also include:
(a) WinStar's requested installation date(s); (b) any excess cable storage
requirements; (c) identification of all Interconnect Facilities and WinStar
Equipment to be installed; (d) a diagram of the desired location of the
Interconnect Facilities and WinStar Equipment; (e) the space, power,
environmental and other requirements for the Interconnect Facilities and WinStar
Equipment; (f) the estimated commencement and termination dates for the
interconnection/collocation; (g) all other information reasonably required by
Williams. Within ten (10) business days of receiving the Interconnection/
Collocation Notice, Williams shall respond to WinStar's
Interconnection/Collocation Notice with its acceptance or objections to
WinStar's proposal in the Interconnect/Collocation Notice.

         4.       Use of Equipment and Interconnect Facilities

         a.       Power Use.  WinStar shall not install any  electrical or other
equipment  that  overloads any  electrical  paneling, circuitry, or wiring.

         b. Standards. WinStar shall ensure that the WinStar Equipment and any
Interconnect Facilities are installed, operated, and maintained to meet or
exceed any reasonable requirements of Williams, any requirements of Williams'
building management or insurance underwriters, and any applicable local, state
and federal codes and public health and safety laws and regulations (including
fire regulations and the National Electric Code).

         c. Intervention. If any part of WinStar's fiber, Interconnect
Facilities or WinStar Equipment is not placed and maintained in accordance with
the terms and conditions of these Collocation Provisions and WinStar fails to
correct the violation within thirty (30) days from receipt of written notice
thereof from Williams, then Williams may, at its option, without further notice
to WinStar, correct the deficiency at WinStar's expense without liability
(except to the extent the Agreement permits recovery for Williams' negligence)
for damages to the fiber,

                                       20
<PAGE>

Interconnect Facilities or WinStar Equipment or for any interruption of
WinStar's services. As soon as practicable thereafter, Williams shall advise
WinStar in writing of the work performed or the action taken. WinStar shall
reimburse Williams for all expenses reasonably incurred by Williams associated
with any work or action performed by Williams pursuant hereto. WinStar shall
remit payment to Williams within thirty (30) days from its receipt of Williams'
invoice therefor.

         d. Threat to Persons or Property. If Williams reasonably determines
that WinStar's actions or failure to fulfill an obligation of these Collocation
Provisions, or its Interconnect Facilities or WinStar Equipment poses an
immediate threat to the safety of Williams' employees or the public, interferes
with the performance of Williams' service obligations, or poses an immediate
threat to the physical integrity of Williams' facilities, Williams may perform
such work and/or take such action that it deems necessary without notice to
WinStar and without subjecting itself to any liability (except to the extent the
Agreement permits recovery for Williams' negligence) for damage to the fiber,
Interconnect Facilities or the WinStar Equipment or for any interruption of
WinStar's services. As soon as practicable thereafter, Williams shall advise
WinStar in writing of the work performed or the action taken. WinStar shall
reimburse Williams for all expenses reasonably incurred by Williams associated
with any work or action performed by Williams pursuant hereto. WinStar shall
remit payment to Williams within thirty (30) days from its receipt of Williams'
invoice therefor.

         e. Use by WinStar's Customers. WinStar may permit its customers holding
IRU interests in the WinStar Fibers to use the collocation rights granted by
these Collocation Provisions, but only as specifically set forth herein. Such
customers shall act as WinStar's subcontractors to the extent they or their
representatives are present at or on space adjoining the Transmission Sites.
WinStar shall be liable for the acts or omissions of such customers to the same
extent as for its own employees or representatives and shall either cause such
customers, their employees and representatives to be covered by WinStar's
insurance coverages as required by the Agreement or shall cause such customers
to independently obtain such insurance. WinStar shall act as the single point of
contact with respect to such customers and Williams. WinStar must provide all
power, space, and additional service to these IRU customers out of WinStar's own
allocation of Basic Services and Ancillary Collocation Services as provided in
these Collocation Provisions.

         5.       Access to Transmission Site.

         a. Access. Williams shall provide WinStar with secure, separate,
unescorted twenty-four (24) hour access to WinStar's assigned space, where
available. Where such separate space is not available, WinStar shall not pay for
escorted access. If WinStar requires access to Williams' common space, it shall
provide Williams with reasonable advance notice and Williams shall provide
escorted access. WinStar shall pay Williams' charges for such access, which may
include minimum call out times, and night, weekend, and holiday differentials or
multipliers. In no case shall WinStar enter Williams common space without a
Williams escort.

                                       21
<PAGE>

         b. Notice. WinStar shall notify the Williams Network Operations Center
prior to entering a Transmission Site.

         c. Security. WinStar shall abide by Williams' reasonable security
requirements. When deemed appropriate by Williams, WinStar employees, customers,
or representatives shall be issued passes or visitor identification cards which
must be presented upon request before entry to Transmission Sites and
surrendered upon demand or upon expiration of the IRU Term. Such passes or other
identification shall be issued only to persons meeting any reasonable security
criteria applicable at the relevant Transmission Site for such purpose. Nothing
in this Subsection shall be construed as preventing WinStar from having
twenty-four hour unescorted access to Transmission Sites.

         d. Right to Terminate Individual's Access. Notwithstanding any other
provision of these Collocation Provisions, Williams shall, without threat of
liability, have the right to immediately terminate the right of access of any
specific WinStar personnel or representative should it determine in its
reasonable discretion for any lawful reason that termination of such access is
necessary for the security of the facility or is required to prevent a violation
of law, landlord requirements, or applicable insurance requirements. Williams
shall promptly notify WinStar of any such termination, and WinStar shall have a
reasonable opportunity to demonstrate that the terminated rights of access
should be reinstated. Any termination of a specific individual's access shall
remain in effect pending Williams' final determination as to the advisability of
such reinstatement.

         e. Removal of WinStar Equipment. Within sixty (60) days after the end
of the IRU Term or WinStar's abandonment of any collocation arrangement at a
Transmission Site, WinStar shall remove all WinStar Equipment from the System or
any other Williams facilities at WinStar's sole cost under Williams'
supervision. WinStar shall provide Williams with at least sixty (60) days'
notice prior to such removal. If WinStar fails to remove the same within said
sixty-day period, Williams shall either:

         (a)      remove WinStar's Equipment and issue an invoice to WinStar for
                  the cost of removal and storage, which WinStar shall pay
                  within thirty (30) days of receipt of such invoice; or

         (b)      notify WinStar that Williams elects to take ownership of such
                  abandoned WinStar Equipment, in which case WinStar shall
                  execute a bill of sale or other document evidencing Williams'
                  title to such WinStar Equipment.

                                       22
<PAGE>

         6. Relocation. WinStar shall, at Williams' expense, relocate its fiber,
Interconnect Facilities and WinStar Equipment within Transmission Site upon
Williams' written request and in the reasonable (under the circumstances) time
frame required by Williams. If the entire Transmission Site is relocated,
Article X (Relocation) of the Agreement shall govern such relocation.

         7. No Restrictions. Williams' right to maintain and operate its
facilities in such a manner as will best enable it to fulfill its own service
requirements is in no manner limited by these Collocation Provisions, except as
specifically set forth in these Collocation Provisions or the Agreement.

         8. Inspections. Williams reserves the right to make periodic
inspections of any part of the Fiber, Interconnect Facilities, or WinStar
Equipment located within or physically attached to the Transmission Sites;
provided that WinStar shall have the right to have one or more of its employees
or representatives present during the time of any such inspection. Williams
shall give WinStar advance notice of such inspections, except in those instances
where Williams determines that safety considerations justify the need for such
an inspection without the delay of providing notice. The making of periodic
inspections or the failure to do so shall not operate to impose upon Williams
any liability of any kind whatsoever nor relieve WinStar of any responsibility,
obligation, or liability allocated to it in these Collocation Provisions.

         9. Liens and Encumbrances. WinStar shall not have the power, authority
or right to create and shall not permit any lien or encumbrance, including,
without limitation, tax liens, mechanics' liens, or other liens or encumbrances
with respect to work performed, in connection with the installation, repair,
maintenance or operation of its WinStar Equipment, Interconnect Facilities or
other property installed within the Transmission Site.

         10. Subordination. WinStar's rights under these Collocation Provisions
shall be totally subordinate to any bona fide mortgages, loans, deeds of trust,
or any other borrowing upon the real or personal property which may be incurred
by Williams. WinStar shall sign any such reasonable documents as are necessary
to satisfy any lender, private or institutional, to reflect said subordination.

         11. Independent Parties. The presence of a Williams or WinStar employee
or representative (as an inspector or otherwise) while an employee or
representative of the other party is at the Transmission Site or performing work
pursuant to these Collocation Provisions shall not make either party liable for
the actions of the other party and shall not be deemed to waive the
responsibility of either party to perform its obligations in a safe and
workmanlike manner.
                                       23
<PAGE>

                                                                       Exhibit C
                                     Part 2

                            POP Collocation Services
                                Services & Terms

1.       Collocation Service:

         1.1      Collocation Service Description ("Collocation Service").

                  WinStar shall have the right to occupy, access and locate
                  therein certain telecommunications transmission equipment and
                  cabling ("Equipment") for the purpose of interconnecting the
                  Equipment with Williams' telecommunications transmission
                  network within a portion of certain premises ("Premises")
                  which are currently owned or leased by Williams. WinStar shall
                  initiate request for Collocation Service by completion of the
                  form included as Attachment I to this Schedule. Collocation
                  Service is granted only by mutual execution of relevant
                  Collocation Service Order(s), identified as Attachment II to
                  this Schedule. The portion of collocation space ("Space")
                  allocated is accepted "as-is" by WinStar and Williams makes no
                  representation as to the fitness of the space for WinStar's
                  intended purpose. WinStar shall abide by the standard
                  specifications as set forth in the Technical Specifications as
                  attached hereto. No work related to Collocation Service shall
                  commence until the CSA, Collocation Schedule, the Collocation
                  Service Request, and the relevant Collocation Service Order(s)
                  are mutually executed.

                  Only upon the express written consent of Williams may WinStar
                  interconnect the Equipment with transmission service provided
                  to WinStar by third parties. If WinStar should interconnect
                  the Equipment with equipment or services of any entity other
                  than Williams without obtaining the written consent of
                  Williams, WinStar shall, subject to the cure provision in the
                  Agreement, be in breach of Agreement and Williams may pursue
                  any legal or equitable remedy, including but not limited to
                  the immediate termination of the license granted in this
                  Schedule.

                  All cross-connections relevant to interconnecting the
                  Equipment with Williams or any other party for which Williams
                  gives explicit written permission shall be established under
                  the control and direction of Williams.

         1.2      Minimum Service Commitment.

                  Collocation Service shall be granted with a minimum network
                  service commitment as further described herein. A minimum
                  multimedia transmission service level of $25,000 per month per
                  rack is required. Transmission charges applied to this
                  commitment level include monthly recurring fees for Private
                  Line, ATM and Frame Relay services. WinStar's monthly
                  transmission billing will be reviewed against the quantity of
                  Collocation Service and WinStar shall be liable for any
                  deficiency. Charges for deficiency will be assessed one month
                  in arrears.

                                       24
<PAGE>

2.       Effective Date: The Effective Date is defined as the date identified on
         the relevant Collocation Service Order as the date of Collocation
         Service delivery, or the date upon which Williams delivers Collocation
         Service, whichever is later.

3.       Term: The Collocation Service Term shall commence upon the Effective
         Date and shall continue for the duration specified within the relevant
         Collocation Service Order.

4.       Rates & Charges: WinStar shall pay Williams for the Collocation
         Services rendered pursuant to this Schedule the charges set forth in
         each Collocation Service Order. Charges shall be payable in advance
         commencing on the Effective Date of the Term relevant to the license
         for the use of the Space and on the first day of each calendar month
         thereafter during the said Term. Charges for partial months shall be
         prorated.

         4.1      Service Fee.

                  The Service Fee is the amount to be invoiced WinStar on a
                  monthly basis for Collocation Service rendered including, but
                  not limited to, space and power use. Service Fees are
                  identified on the relevant Collocation Service Order.

         4.2      Installation Fee.

                  The Installation Fee is the amount to be invoiced WinStar as a
                  one time fee for Collocation Service consisting of charges
                  associated with the initial installation of the Collocation
                  Service. Installation Fees are identified on the relevant
                  Collocation Service Order.

         4.3      Build-Out Fee.

                  Build-Out Fees are those one-time charges applicable to
                  Collocation Services rendered that are outside the standard
                  Collocation offering. Build-Out fees are individually quoted
                  based on Service Order. Build-out fees are payable in full to
                  Williams upon execution of a Collocation Service Order and no
                  work will be performed by Williams or WinStar to Build-Out
                  space prior to Williams' receipt of said payment. Alterations
                  to the form or amount of this payment must be requested by
                  WinStar in writing and approved by Williams Finance &
                  Administration prior to commencement of work.

        4.4      Ancillary: Ancillary charges related to changes of Collocation
                 Service delivery are fully defined in Section 9 of this
                 Collocation Schedule.

                                       25
<PAGE>

<TABLE>
<CAPTION>
- -------------------------------------------------------------------- -----------------
                                                                     Charge  Per
                                                                     Occurrence
- -------------------------------------------------------------------- -----------------
<S>                                                                      <C>    
Change of Effective Date (pre-install)                                   $100.00
- -------------------------------------------------------------------- -----------------
Change of Collocation Service Order (pre-Effective Date)                 $100.00
- -------------------------------------------------------------------- -----------------
Change of Collocation Service (post-Effective Date)                      $250.00
- -------------------------------------------------------------------- -----------------
Order Cancellation (greater than/=30 days from Effective Date)           $250.00
- -------------------------------------------------------------------- -----------------
Order Cancellation (less than 30 days from Effective Date)               $500.00
- -------------------------------------------------------------------- -----------------
AC power addition (post Effective Date)                                  $750.00
- -------------------------------------------------------------------- -----------------
</TABLE>

     4.5  Dispatch Labor Charges: are assessed for WinStar requested site labor.
          Dispatch requires 10 days advance notice to Williams.

          -------------------------------- ------------------------
                                 Charge Per Hour
          -------------------------------- ------------------------
          M-F Business Hours               $100.00
          -------------------------------- ------------------------
          M-F Off Business Hours           $125.00
          -------------------------------- ------------------------
          Sat & Sun                        $150.00
          -------------------------------- ------------------------
          Holidays                         $150.00
          -------------------------------- ------------------------

5.       Collocation Service Delivery: Upon mutual acceptance of a Collocation
         Service Order, Williams shall confirm Effective Date, or inform WinStar
         of the estimated date for the delivery of such Collocation Service.
         Williams shall use reasonable efforts to install each Collocation
         Service on or before the Effective Date, but the inability of Williams
         to deliver a facility by such date shall not be a default under this
         Schedule.

         In the event Williams fails to tender possession of the Space to
         WinStar by the Effective Date, WinStar shall not be obligated to pay
         the Service Fee or Installation Fee until such time as Williams tenders
         possession of the Space to WinStar.

         If Williams fails to make Collocation Services available within ninety
         (90) days after the Effective Date (due to any reason other than the
         acts or omissions of WinStar), winter's sole remedy shall be to cancel
         the Collocation Service Order which pertains to such Collocation
         Service by written notice to Williams. Williams shall not be liable to
         WinStar in any way as a result of such delay or failure to tender
         possession.

6.       Contract Expiration: Following the expiration of the term or failure of
         the parties to enter into any renewal periods, WinStar's license shall
         continue in effect on a month-to month basis upon the same terms and
         conditions specified within this Schedule and relevant Collocation
         Service Order, unless terminated by either WinStar or Williams upon
         thirty (30) days prior written notice.

                                       26
<PAGE>

         WinStar's option to renew its license to occupy the Space shall be
         contingent on the election by Williams to continue to own or lease the
         premises in which the Space is located for the duration of the renewal
         period(s), such election to be exercised at the sole discretion of
         Williams.

7.       Early Termination: WinStar may terminate Collocation Service upon 30
         days written notice. Collocation Services will be terminated 30 days
         from date of letter and WinStar will be liable for fifty percent (50%)
         of the charges due under remaining term of contract should WinStar
         terminate Collocation Service prior to contract expiration. Termination
         Liability will be invoiced in lump sum in the billing period directly
         following Collocation Service termination and shall be payable within
         30 days of the invoice date.

8.       [Intentionally Blank

9.       Change of Collocation Services:

         9.1      Change of Effective Date (pre-install). WinStar will be
                  assessed a Change of Effective Date Charge by Williams for any
                  changes of Effective Date requested within thirty (30) days
                  prior to original Effective Date. WinStar will also be charged
                  for any charges incurred by Williams from third party
                  providers as a result of a request by WinStar for a Change of
                  Effective Date, regardless of date of WinStar notification.

         9.2      Change of Collocation Service Order (pre-Effective Date). All
                  modifications to the information contained in an executed
                  Collocation Service Order will be reviewed on an individual
                  case basis and the Collocation Service Order shall be amended
                  accordingly upon Williams' acceptance of the Collocation
                  Service modifications. Any modifications will permit Williams
                  to likewise amend Rates and Charges and Effective Date from
                  original Collocation Service Order. WinStar will be assessed a
                  one time fee for changes to a Collocation Service Order.
                  WinStar will also be charged for any charges incurred by
                  Williams from third party providers as a result of a request
                  by WinStar for a Change of Collocation Service Order,
                  regardless of date of WinStar notification.

         9.3      Change of Collocation Service (post-Effective Date). If
                  WinStar requests a change to Collocation Services after such
                  Collocation Services have been installed, the request will be
                  reviewed by Williams on an individual case basis with no
                  guarantees granted by Williams as to the ability to provide
                  such enhanced Collocation Service. All Change of Collocation
                  Service requests shall be authorized by Williams via a change
                  Collocation Service Order. WinStar may incur an additional
                  Collocation Service and/or Installation Fee(s) for the amended
                  Collocation Service. WinStar will be assessed a one time fee
                  for Collocation Service changes. WinStar will also be charged
                  for any charges incurred by Williams from third party
                  providers as a result of a request by WinStar for a Change of
                  Collocation Service, regardless of date of WinStar
                  notification.

                                       27
<PAGE>

          9.4  Order Cancellation (>/=30 days from Effective Date). WinStar may
               cancel a Collocation Service Order by written notice to Williams.
               WinStar will incur a one time cancellation fee for Collocation
               Services cancelled where notice is received at least 30 days
               prior to Effective Date.

          9.5  Order Cancellation (less than 30 days from Effective Date).
               WinStar may cancel a Collocation Service Order by written notice
               to Williams. WinStar will incur a one time cancellation fee for
               Collocation Services cancelled where notice is received less than
               30 days prior to Effective Date.

10.      Improvements to Space: In the event WinStar desires to make
         improvements to the Space which improvements are deemed material and
         substantial as reasonably determined by Williams ("Material
         Improvements"), WinStar shall submit all plans and specifications for
         such work to be performed in the Space to Williams for Williams' prior
         written approval, which approval shall not be unreasonably withheld or
         delayed. No construction for Material Improvements may commence until
         the foregoing consent is obtained. WinStar agrees that its use or
         construction of the Space shall not interfere with Williams' use of its
         Premises or other tenants' use of their premises in the building in
         which the Premises are located.

         WinStar shall not employ any contractor to perform Material
         Improvements unless previously approved in writing by Williams, which
         approval shall not be unreasonably withheld (and approved in writing by
         the Landlord if required by the lease). WinStar and each contractor and
         subcontractor participating in performing material Improvements shall
         warrant that such work shall be free from all mechanic's and/or
         materialman's liens and free from any and all defects in workmanship
         and materials for the period of time which customarily applies in good
         contracting practice, but in no event for less than one (1) year after
         the acceptance of the work by WinStar and Williams. The aforesaid
         warrantees of each such contractor and subcontractor and WinStar shall
         include the obligation to repair or replace in a workmanlike manner all
         defects in workmanship and materials without any additional charge.

         It shall be WinStar's responsibility to cause each of WinStar's
         contractors and subcontracts to maintain continuous protection of the
         premises adjacent to the Space in such manner as to prevent any damage
         to such adjacent property by reason of the performance of WinStar's
         work.

                                       28
<PAGE>

         All of WinStar's work shall be coordinated with all work being
         performed or to be performed by Williams and other tenants of the
         building in which the Premises are located. The contractor or
         subcontractor shall not at any time damage, injure, interfere with or
         delay the completion of any other construction within the building; and
         they and each of them shall comply with all procedures and regulations
         prescribed by Williams and the Landlord of the Premises for integration
         of winter's work with the work to be performed in connection with the
         construction of the building, and all other construction within the
         building which comprises or contains the Premises.

         All fixtures, alterations, additions, repairs, improvements and/or
         appurtenances attached to or built into, on or about the Space prior to
         or during the Term of the license relevant thereto, whether by Williams
         at its expense or at the expense of WinStar, or by WinStar at its
         expense or by previous occupants of the Space, shall be and remain part
         of the Space and shall not be removed by WinStar at the end of the Term
         of the license relevant to the Space. Upon termination or expiration of
         the Term relevant to the Space, Williams shall allow WinStar thirty
         (30) days from the date of such termination or expiration, at WinStar's
         sole cost and expense, to remove all trade fixtures (including, but not
         limited to, rectifiers/chargers, batteries, AC power conditioning
         equipment, telecommunication switching equipment, channel banks, etc.)
         installed by WinStar provided that the Space is restored by WinStar to
         its condition before the installation of such items and that all such
         work (including restoration) is performed in accordance with the other
         provisions of this Schedule. If WinStar shall fail to complete such
         removal and restoration within the aforesaid thirty (30) day time
         period, all such trade fixtures remaining within the Space or at the
         Premises may, at Williams' option, become the sole property of
         Williams, and Williams may dispose of such trade fixtures as it deems
         appropriate. WinStar shall continue to pay the Service Fee specified in
         the relevant Collocation Service Order until the earlier of: (i)
         WinStar's removal of such trade fixtures and completion of such
         restoral or (ii) Williams' taking possession of such trade fixtures as
         set forth above.

         All work affecting the Space shall be in compliance with all laws,
         ordinances, rules, regulations, orders and directives of governmental
         and quasi-governmental bodies and authorities having jurisdiction over
         the Premises and the Space from time to time and WinStar shall obtain
         and keep in effect all licenses, permits and other authorizations
         required with respect to the business conducted by WinStar within the
         Space.

     11.  Sole Use of Space by WinStar: WinStar acknowledges that it has been
          granted only a license to occupy the Space and that it has not been
          granted any real property interests in the Space and that neither this
          Schedule nor any interest created herein shall be assigned, mortgaged,
          subleased, encumbered or otherwise transferred, and that neither the
          Space nor any part thereof shall be encumbered in any manner by reason
          of any act or omission on the part of WinStar, or used or occupied, or
          permitted to be used or occupied, by anyone other than WinStar. Any
          attempt to allow the use or occupation of the Space by anyone other
          than WinStar to assign, mortgage, sublease or encumber any rights
          under this Schedule by WinStar shall, unless otherwise agreed to in
          writing by Williams, be void and in such event, Williams shall have
          the right to terminate this Schedule as to any or all Space occupied
          by WinStar. Such written agreement by Williams shall be subject to the
          sole discretion of Williams.

                                       29
<PAGE>

     12.  Eminent Domain: In the event of a taking by eminent domain (or a
          conveyance by any Landlord of all or any portion of the Premises to an
          entity having the power of eminent domain after receipt of actual
          notice of the threat of such taking) of all or any portion of the
          Premises so as to prevent, in Williams' sole discretion, the
          utilization by WinStar of the Space in the Premises, relevant
          Collocation Service Order(s) shall terminate as of the date of such
          taking or conveyance with respect to the Space which is affected by
          such taking or conveyance and the Service Fee paid or to be paid by
          WinStar shall be reduced accordingly. Except as set forth below,
          WinStar shall have no claim against Williams for the value of the
          unexpired Term of the license affected thereby (or any portion
          thereof) or any claim or right to any portion of the amount that might
          be awarded to the Landlord of the Premises or Williams as a result of
          any such payment for condemnation or damages. Nothing contained in
          this Schedule should prohibit WinStar from seeking any relief or
          remedy against the condemning authority in the event of an Eminent
          Domain proceeding or condemnation which affects the Space.

     13.  Damage to Premises: If the building in which the Premises are located
          is damaged by fire or other casualty, Williams shall give immediate
          notice to WinStar of such damage. If a Landlord or Williams exercises
          an option to terminate a particular Lease due to damage or destruction
          of the Premises subject to such Lease, or if Williams decides not to
          rebuild such building or portion thereof in which the Space is
          located, relevant Collocation Service Order(s) shall terminate as of
          the date of such exercise or decision as to the affected Space and the
          Service Fee paid by WinStar shall be modified accordingly. If neither
          the Landlord of the affected Premises nor Williams exercises the right
          to terminate, Williams shall repair the particular Space to
          substantially the same condition it was in prior to the damage,
          completing the same with reasonable speed. In the event that Williams
          shall fail to complete the repair within a reasonable time period,
          WinStar shall thereupon have the option to terminate relevant
          Collocation Service Order(s) with respect to the affected Space, which
          option shall be the sole remedy available to WinStar against Williams
          under this Schedule relating to such failure. If the Space or any
          portion thereof shall be rendered untenable by reason of such damage,
          the Service Fee for such Space shall proportionately abate, based on
          the amount of square footage which is rendered untenable, for the
          period from the date of such damage to the date when such damage shall
          have been repaired for the portion of the Space rendered untenable.

     14.  Conduct in Space & Premises: WinStar shall abide by Williams' and
          applicable landlord's rules with regard to conduct in the Premises.
          Such rules include, but are not limited to, a prohibition against


                                       30
<PAGE>

          smoking in the Space or the Premises by WinStar's employees, agents,
          representatives, contractors, subcontractors, invitees or licensees.
          Further, WinStar shall maintain the Space in a safe condition,
          including but not limited to the preclusion of storing combustible
          materials in the Space.

                                      31
<PAGE>


                                                                       Exhibit C
                               Part 2 (Continued)
                 TECHNICAL SPECIFICATION FOR COLLOCATION SERVICE

Williams Network Standards, Descriptions & Tasks

1.0      DC Power

         1.1      Backup electrical power, including batteries and shared use of
                  an emergency generator to the extent such generator exists and
                  is maintained to support the Premises.

         1.2      DC power adequate for WinStar's consumption equated to power
                  specified in applicable Collocation Service Order. A
                  low-voltage and high-voltage battery alarm will be monitored
                  by Williams.

         1.3      Nominal 50 +/- 6V DC battery and charger supply with a minimum
                  four (4) hour reserve will be provided by Williams.

         1.4      Redundant chargers of adequate size will be provided by
                  Williams, so that in the event of a charger failure the full
                  load will be supplied to WinStar's equipment. A charger
                  failure alarm will be monitored by Williams.

2.0      AC Power

         2.1      A 20-amp four-plex AC receptacle will be available within
                  reach of WinStar's Equipment. AC power and outlets for use
                  with test equipment only and is not provided to operate the
                  Equipment. This AC power is not provided over an
                  Uninterruptable Power Source (UPS).

         2.2      AC power supply to WinStar equipment is backed by generator
                  where available, but is not UPS. This excludes utility outlets
                  described in the immediately preceding subsection 2.1.

3.0      Environmentals

         3.1 Pre-reaction sprinkler protection, where available. Smoke and fire
             alarms monitored by Williams.

         3.2 Lighting.

         3.3 Ground Buss and cable interconnect.

         3.4 Grounding conductor will be supplied by Williams between the bus
             bar and WinStar's Equipment.

                                       32
<PAGE>

         3.5 Overhead cable ladder

         3.6 Interconnect signal and power cabling between Williams and 
             WinStar.

         3.7 Concrete floors will be covered with vinyl tile.

         3.8 Ambient temperature will be maintained by Williams between
             60-90(degree)F with an objective of 20-65% humidity.

         3.9 General and administrative services directly relating to the
             provision of the above listed Collocation Services.

WinStar Standards, Descriptions & Tasks

1.0      Equipment Specifications

         1.1      The Equipment should be designed to operate satisfactorily
                  between 60-90(degree)F with 20-65% (non-condensing) humidity.
                  Low 60(degree) and high 90(degree) temperature alarms will be
                  monitored by Williams.

         1.2      WinStar will ensure that their equipment and surrounding area
                  do not pose safety hazards to personnel. This includes exposed
                  AC electrical hazards, trip and slip hazards, hazardous
                  material storage deficiencies, improperly secured or
                  overloaded equipment racks or ladders, inadequate ingress and
                  egress space. OSHA and local codes will apply.

         1.3      WinStar will notify Williams of any significant equipment
                  additions or deletions (i.e. shelf or rack). Installation and
                  removals will be coordinated with local Williams management.

2.0      Space Specifications

         2.1      WinStar will not jeopardize Collocation Service or damage
                  property of other collocated customers, Williams, or landlord
                  in any manner.

         2.2      WinStar will take precautions to protect Williams' and
                  landlord's common facility and nearby equipment belonging to
                  other customers. This includes floor, wall, and
                  telecommunication equipment protection while moving equipment
                  and notifying Williams of any major rearrangements of
                  equipment, drilling, power work, and etc.

         2.3      WinStar will follow good housekeeping practices. All trash
                  must be disposed of daily at WinStar's expense. Any trash or
                  empty boxes not disposed of by WinStar is subject to removal
                  by Williams with any associated charges borne by WinStar.

                                       33
<PAGE>

         2.4      Nothing may be stored outside of the assigned rack space.  A 
                  minimum of 2.5'  of aisle space must be maintained at
                  front and rear of equipment.

         2.5      No metal ladders, stools, or chairs may be used.

         2.6      Combustible or hazardous material may not be stored in the 
                  area.

         2.7      All equipment must be installed within the assigned rack 
                  footprint (i.e. UPS units, spare equipment).

         2.8      All cabling will be terminated on DSX panels in the Williams
                  common area. Fiber will be terminated on an appropriate Fiber
                  Distribution Panel ("FDP"). Any panels for WinStar end will be
                  supplied at WinStar's expense.

         2.9      WinStar is responsible for the termination of the A & B DC 
                  power and signal cabling in its Equipment.

         2.10     Maximum DC power provided to WinStar as A & B power shall be
                  rated for the rating of a single feed. WinStar is liable for
                  an outage caused by the DC power exceeding the single feed
                  rating. WinStar will be responsible for payment of consumed
                  power exceeding the single feed rating specified in the
                  Collocation Service Order.

         2.11     WinStar will follow normal telecommunications industry
                  standards with regards to equipment installation and removal
                  in a central office environment. Williams standards are to be
                  followed for connection of cables that interface with
                  Williams. All installations are subject to approval by
                  Williams.

         2.12     Permanent use of extension cords is not allowed.

         2.13     WinStar will not jeopardize Williams' ability to conduct 
                  business in any manner.

         2.14     All local, state, and federal laws will be obeyed. Local
                  requirements for union labor, especially for AC electrical
                  work, will be observed. Building management guidelines will be
                  followed.

         2.15     WinStar will follow Williams sign-in procedures at all times.
                  Subject to the requirements of this Schedule, WinStar shall
                  have access to their equipment 24 hours a day, 365 days a
                  year. WinStar must coordinate their first visit to a
                  particular Williams' site with Williams' operations
                  department, giving at least five (5) days notice of such
                  visit. For all subsequent entries, WinStar will follow the
                  procedure outlined below:

                                       34
<PAGE>

          (a)  At locations where WinStar's equipment is located in caged space
               which is separate from Williams' equipment, before entry WinStar
               will notify Williams' Network Control Center at (800) 582-9069
               and follow Williams' sign-in procedures.

          (b)  At locations where WinStar's equipment is not located in caged
               space which is separate from Williams' equipment, WinStar must be
               escorted by a Williams technician. WinStar may gain such escort
               by notifying Williams' Network Control Center at (800) 582-9069
               at least forty-eight hours prior to WinStar's desired entry. In
               the case of an emergency, WinStar shall give as much notice as is
               reasonably possible by contacting Williams' Network Control
               Center at the number listed above. Williams' Network Control
               Center shall work with WinStar to allow WinStar to gain access as
               soon as reasonably possible.

          2.16 If Williams notifies WinStar in writing of a violation of the
               above rules, or any other unsafe or unacceptable situation or
               practice, WinStar must correct the problem within seven days or
               provide a written plan for correction to Williams' satisfaction
               and proposed completion date. Williams may agree to additional
               time. If the problem is not resolved in seven days or within the
               agreed upon time frame, which ever is longer, Williams may fix
               the option of either (i) correcting the problem at WinStar's
               expense or (ii) terminating the contract and diconnecting power
               and signal connections from WinStar's equipment.

               Extreme safety violations are subject to immediate correction by
               Williams without prior notice to WinStar. Corrections made by
               Williams are at WinStar's expense and will be billed to WinStar
               on a time and material basis.

                                       35
<PAGE>


                            Exhibit C - Attachment I

                                Reference Number  ________________________
                                                    new   |_|        disc   |_|
                                                    sup   |_|        cancel |_|
                                                    change |_|

                      [WILLIAMS COLLOCATION SERVICE REQUEST]






                                       36
<PAGE>


                       [WILLIAMS COLLOCATION SERVICE ORDER]
                                  [CONTINUED]

                                       37
<PAGE>


                                    EXHIBIT D
                Fiber Splicing, Testing and Acceptance Standards

1.       Initial Construction Testing

         A. During initial construction, Williams shall use an optical time
domain reflectometer ("OTDR") to test splices and shall use an OTDR and a 1-km
launch reel to test pigtail connectors. Such initial construction tests shall be
uni-directional and performed at 1550 nm.

         B. If the loss value of two connectors and the associated pigtail
splice exceeds 1 dB, Williams shall break the splice and re-splice until the
loss value is 1.0 dB or less. If Williams is unable to achieve a loss value of
1.0 dB or less after five total splicing attempts, the splice shall be marked as
Out-of-Spec (OOS).

         C. If the loss value for a splice, when measured in one direction with
an OTDR, exceeds 0.15 dB, Williams shall break the splice and re-splice until
the loss value is 0.15 dB or less, provided that, if Williams is not able to
achieve a loss value of 0.15 dB after three total splicing attempts, then the
maximum loss value shall be 0.3 dB. If, after two additional resplicing
attempts, Williams is not able to achieve a loss value of 0.3 dB or less, then
Williams shall mark the splice as Out-of-Spec (OOS).

2.       End-to-End Testing

        A. After Williams has established end-to-end connectivity on the fibers
during initial construction, it shall:

o    perform bi-directional end-to-end tests,

o    test continuity to confirm that no fibers have been "frogged" or crossed in
     any of the splice points,

o    record loss measurements using a light source and a power meter, and

o    take OTDR traces and record splice loss measurements.

       B. Williams shall perform the bi-directional end-to-end tests and
OTDR traces at both 1310 nm and 1550 nm. Williams shall measure and verify
losses for each splice point in both directions and average the loss values.
Williams shall mark any splice points as Out-of-Spec (OOS) that have an average
loss value, based on bi-directional OTDR testing at 1550 nm, in excess of 0.3
dB.


<PAGE>
                                       38

3.       Post-Construction Testing

After performing permanent resplicing (in conjunction with repair of a cable
cut, replacement of a segment of cable, or other work after initial installation
and splicing of the cable), the test procedures set forth in section 2
(End-to-End Testing), shall apply to the relevant fibers and cable segments. The
provisions in sections 4 (OTDR Equipment and Settings) and 5 (Acceptance Test
Deliverables), that are relevant to such testing shall also apply. Williams may,
after completing construction of its System, adopt any alternative methods of
testing that are generally accepted in the industry and that provide sufficient
data to fulfill the objectives of the tests set forth in this exhibit.


4.       Out-of-Spec Splices

         Out-of-Spec splices shall be noted, but shall not preclude acceptance
of a fiber if the Out-of-Spec condition does not affect transmission capability
(based on use of then-prevailing telecommunications industry standards
applicable to equipment generally used with the relevant type of fiber) or
create a significant possibility of an outage.

5.       OTDR Equipment and Settings

         A. Williams shall use OTDR equipment and settings that are, in its
reasonable opinion, suitable for performing accurate measurements of the fiber
installed. Such equipment and settings shall include, without limitation, the
equipment and settings described below.

         B. Williams has approved the following OTDRs and settings for
acceptance testing: the Laser Precision TD3000 and CMA4000 models and compatible
models.

         C. Williams has approved the following settings for various OTDR tests:

i.       Index of refraction settings:

  
                                            1310 nm          1550 nm
         ---------------------------------- ---------------- -----------------
           Lucent Truwave                    1.4738          1.4732
           Corning SMF-28                    1.4675          1.4681
           Corning SMF-LS                    1.471           1.470
           Corning LEAF                      1.470           1.469
           Sumitomo fiber                    1.4670          1.4670

                                       39
<PAGE>

ii.      Tests of a pigtail connector and its associated splice:

                TD3000                               CMA4000
               -------------------------- ----------------------------
                4 km Range                 4 km Range
                50 ns Pulse                50 ns Pulse
                1 m Resolution             1 m Resolution
                Medium Averaging           Medium Averaging

iii.     End to End Segment OTDR Testing:


                TD3000                               CMA4000
                -------------------------- ----------------------------
                64 km Range                100 km Range
                500 ns Pulse               250 ns Pulse
                4 m Resolution             4 m Resolution
                Medium Averaging           Medium Averaging


         Note: If the end points are more than 64 kilometers apart, Williams
         currently uses a TD3000 set at 128 km range setting and performs
         bi-directional testing only at 1550 nm.

6.       Acceptance Test Deliverables

         Williams shall provide data sheets or computer media containing the
following information for the relevant fibers and cable segments:

              A. Verification of end-to-end fiber continuity with power level
     readings for each fiber taken with a light source and power meter.

              B. Verification of loss at each splice point to be below 0.3 dB as
     well as the final bi-directional OTDR test data, with distances.

              C. Cable manufacturer, cable type (buffer/ribbon), fiber type,
     cable reel number, number of fibers, number of fibers per tube, and
     distance of each section of cable between splice points.

                                       40
<PAGE>


  
                                    EXHIBIT E

                              FIBER SPECIFICATIONS

         Exhibit A, Part 2 sets forth the types of fibers for each System
Segment. The corresponding attached manufacturer's specifications shall apply to
each System Segment as indicated therein.

         Williams may, with WinStar's consent, which shall not be unreasonably
withheld, substitute a different type of fiber for a System Segment if such type
is equivalent or superior to the type set forth in Exhibit A, Part 2 for such
System Segment, by written notice provided at least one hundred twenty (120)
days before the planned Acceptance Date for such System Segment. Such written
notice shall include the relevant manufacturer's specifications for such fiber
type and such specifications shall, if WinStar consents to such substitution,
apply to such System Segment.

         Specifications for SMF-28, SMF-LS, and SMF-LEAF fibers are attached.

                                       41
<PAGE>


                                    EXHIBIT F
                        Cable Installation Specifications


1.   Material 

o    Steel or PVC conduit shall be minimum schedule 40 wall thickness.

o    Any exposed steel conduit, brackets or hardware (e.g., bridge attachments)
     shall be hot-dipped galvanized after fabrication. o All split steel shall
     be flanged.

o    Handholes shall have a minimum H-15 loading rating.

o    Manholes shall have a minimum H-20 loading rating.

o    Warning signs shall display universal do not dig symbol, "Warning-Buried
     Fiber-Optic Cable," company name and logo, local and emergency One Call
     toll-free numbers.

2.       Minimum Depths

Minimum cover required in the placement conduit/cable shall be forty-two inches
(42"), except in the following instances: 

o    The minimum cover in ditches adjacent to roads, highways, railroads and
     interstates is forty-eight inches (48") below the clean out line or
     existing grade, whichever is greater.

o    The minimum cover across streams, river washes, and other waterways shall
     be sixty inches (60") below the clean out line or existing grade, whichever
     is greater.

o    At locations where fiber-optic cable crosses other subsurface utilities or
     other structures, the fiber-optic cable/conduit shall be installed to
     provide a minimum of twelve inches (12") of vertical clearance from the
     utility/obstacle. The fiber-optic cable/conduit can be placed above the
     utility/obstacle, provided the minimum clearance and applicable minimum
     depth can be maintained; otherwise the fiber optic cable/conduit shall be
     installed under the existing utility or other structure.

o    In rock, the cable/conduit shall be placed to provide a minimum of eighteen
     inches (18") below the surface of the solid rock, or provide a minimum of
     forty-two inches (42") of total cover, whichever requires the least rock
     excavation.

o   Where existing pipe is used, current depth is sufficient.

                                       42

<PAGE>
3.   Buried Cable Warning Tape

o    All cable/conduit shall be installed with buried cable warning tape. The
     warning tape shall be laid a minimum of twelve inches (12") above the
     cable/conduit. The warning tape shall generally be placed at a depth of
     twenty-four inches (24") below grade and directly above the cable/conduit.

o    Buried cable warning tape shall be a minimum of three inches (3") wide and
     display "Warning-Buried Fiber-Optic Cable," a company name, logo and
     emergency One Call toll-free number repeated every twenty-four inches
     (24").

4.       Conduit Construction

o    Conduits may be placed by means of trenching, plowing, jack and bore,
     multi-directional bore or directional bore. Conduits shall generally be
     placed on a level grade parallel to the surface, with only gradual changes
     in grade elevation.

o    Steel conduit shall be joined with threaded collars, Zap-Lok or welding.
     (Welding is the preferred method.)

o    All crossings of paved city, county, state, federal, and interstate
     highways, or railroad crossings shall be encased in steel conduit.

o    All longitudinal cable runs under paved streets shall be placed in steel or
     concrete encased PVC conduit.

o    All cable placed in metropolitan areas shall be placed in steel or concrete
     covered PVC conduit.

o    Metropolitan areas shall be defined as areas where there is either
     extensive development and improvement or rapid growth (new building
     construction).

o    All crossings of major streams, rivers, bays and navigable waterways shall
     be placed in HDPE, PVC or steel conduit, or shall use specially armored
     submarine cable. 

o    At all foreign utility/underground obstacle crossings, steel conduit shall
     be placed and shall extend at least five feet (5') beyond the outer limits
     of the obstacle in both directions.

o    All jack and bores shall use steel conduit.

o    All directional or mini-directional bores shall use HDPE or steel conduit.

o    Any cable placed in swamp or wetland areas shall be placed in HDPE, PVC or
     steel conduit.

5.       Innerduct Installation

o    Innerduct(s) shall be installed in all steel conduits. No cable shall be
     placed directly in any split/solid steel conduit without innerduct

                                       43

<PAGE>

o    Innerduct(s) shall extend beyond the end of all conduits a minimum of
     eighteen inches (18").

6.       Cable Installation in Conduit

The fiber-optic cable shall be installed using either a sealed pneumatic cable
blowing system or a powered pulling winch and hydraulic powered assist pulling
wheels. The maximum pulling force to be applied to the fiber-optic cable shall
be six hundred pounds (600 lbs.). Sufficient pulling assists shall be available
and used to insure the maximum pulling force is not exceeded at any point along
the pull. 

o    The cable shall be lubricated at the reel and all pulling assist locations.

o    A pulling swivel breakaway rated at six hundred pounds (600 lbs.) shall be
     used at all times.

o    Splices shall only be allowed at planned junctions and reel ends.

o    All splices shall be contained in a handhole or manhole.

o    A minimum of twenty meters (20m) of slack cable shall be left in all
     intermediate handholes and manholes.

o    A minimum of thirty meters (30m) of slack cable shall be left in all splice
     locations.

o    A minimum of fifty meters (50m) of slack cable shall be left in
     Transmission Sites and points of presence.

o    PVC conduit or innerduct may be split, with the fiber-optic cable installed
     inside the split duct and plowed in.

7.       Manholes and Handholes

o    Manholes shall be placed in traveled surface streets and shall have locking
     lids.

o    Handholes shall be placed in all other areas, and be installed with a
     minimum of eighteen inches (18") of soil covering lid.

8.       EMS Markers

EMS Markers shall be placed directly above the lid of all buried handholes. EMS
markers fabricated into the lids of the handholes are acceptable.

9.       Cable Markers (Warning Signs)

Cable markers shall be installed at all changes in cable running line direction,
splices, pull boxes, assist-pulling locations, and at both sides of street,
highway or railroad crossings. Markers shall be spaced at intervals of no more
than five hundred feet (500') apart in metropolitan areas and within line of
sight (not to exceed one thousand feet (1,000')) in non-metropolitan areas.
Markers shall be positioned so that they can be seen from the location of the
cable and generally set facing perpendicular to the cable running line.


                                       44
<PAGE>


Splices and pull boxes shall be marked on the cable marker post.

10.      Fiber Optic Groundwire

The Williams Communications, Inc. (Vyvx) Optical Groundwire Specifications
(Issue 1; October 15, 1996) shall apply to optical groundwire (aerial fibers
installed within power transmission groundwire cable). Sections 2 through 9 of
these Cable Specifications shall be inapplicable to optical groundwire. Upon
written request, Williams shall promptly provide a copy of its Optical
Groundwire Specifications.

11.      Updating of Specifications

Williams may revise these Cable Installation Specifications to include new
procedures, materials, or processes so long as the changes achieve the
objectives of the specifications set forth above and are in accordance with, or
superior to, then-current telecommunications industry standards.



                                       45

<PAGE>


                                      EXHIBIT G
                        Transmission Site Specifications

         All Transmission Sites shall have redundant HVAC (heating, ventilation,
and air conditioning) units each capable of handling the site's full HVAC load.

         All unattended (unmanned) Transmission Sites shall have a minimum of
eight (8) hours' battery reserve.

         All attended Transmission Sites without an on-site generator shall have
a minimum of eight (8) hours' battery reserve. If there is no generator on site,
Williams shall have a portable generator at the Transmission Site within eight
(8) hours of a power failure.

         All attended Transmission Sites with an on-site generator shall have a
minimum of four (4) hours' battery reserve.

         All on-site generators shall be capable of powering the total site for
a minimum of twenty-four (24) hours. All generators shall have auto-start and
auto-load transfer capabilities. All generators shall be inspected, tested, and
refueled (to replace consumed fuel) once per month.

         Williams shall use approximately forty-mile spacing between
Transmission Sites (or between a Transmission Site and a point of presence or
System end point), except where geographic factors dictate shorter spacing.

         All Transmission Site buildings shall be grounded with a target
specification of 5 ohms or less. The Cable sheath will be exposed and grounded,
typically at least fifty (50) cable feet before the entrance to the building
transition of outside plant to inside plant cabling.

                                       46
<PAGE>


                                    EXHIBIT H
                         As-Built Drawing Specifications


1.       As-Built Alignment Sheets

         Survey information (either from existing data or new information) shall
         be put on drawings.

         Drawings shall contain cable information, splice locations, assist
         point locations with permanent structures, survey stations, conduit
         information, Transmission Site locations, and optical distances to the
         nearest Transmission Sites from each splice location.

         Drawings shall be updated with actual field data during and after
         construction.

         Metropolitan area scales shall not exceed 1" = 200'.

         Non-metropolitan area scales shall not exceed 1" = 500'.

         Drawings shall be "blue lines", as such term is understood in the
         industry or in Auto CAD format revision 13 or a later revision.
         Williams may, after completing construction of its System, adopt any
         replacement method of creating or providing drawings that is generally
         accepted in the industry and that provides equivalent information.

2.       Transmission Sites

         Floor plans shall show rack placement and assignment for WinStar's
         floor space.

                                       47
<PAGE>


                                    EXHIBIT I
                            Operations Specifications

1.       Routine Maintenance

Williams shall perform the work and provide the services set forth in the
following paragraphs A through E as Routine Maintenance:

         A. NCC Functions. Williams shall operate a manned Network Control
Center ("NCC") twenty-four (24) hours a day, seven (7) days a week that monitors
the System by means of remote surveillance equipment and dispatches maintenance
and repair personnel to handle and repair problems detected through by the NCC
or reported by WinStar or other parties. Williams shall provide WinStar a
toll-free telephone number to report problems to the NCC.

         B. Cable Maintenance. Williams shall perform appropriate routine
maintenance on the Cable in accordance with Williams' then current preventative
maintenance procedures. Williams' preventative maintenance procedures shall not
substantially deviate from industry practice.

         C. Transmission Site Maintenance. Williams shall perform appropriate
routine maintenance on regenerator, optical amplifier, and junction buildings,
including the DC power plant, HVAC equipment, and basic building safety
equipment including alarms and emergency generators in accordance with Williams'
then current preventative maintenance procedures. Williams' preventative
maintenance procedures shall not substantially deviate from industry practice.

         D. Route Patrol. Williams shall patrol the Route on a reasonable,
routine basis and shall perform all required Cable locates. Williams shall
belong to a state or regional one-call (call-before you dig) center when
available.

         E. Spare Cable. Williams shall maintain an inventory of spare Cable at
strategic locations to facilitate timely restoration.

2.       Planned Network Maintenance Activity

Williams shall avoid performing maintenance between 0600-2200 local time, Monday
through Friday, inclusive, that will have a disruptive impact on the continuity
or performance level of WinStar Property. However, the preceding sentence does
not apply to restoration of continuity to a severed or partially severed fiber
optic cable, restoration of dysfunctional power and ancillary support equipment,
or correction of any potential jeopardy conditions. Williams shall provide
WinStar with telephone, facsimile, or written notice of all non-emergency
planned network maintenance (a) no later than 3 working days prior to performing
maintenance that, in its reasonable opinion, has a substantial likelihood of
affecting WinStar's traffic for up to 50 milliseconds, and (b) no later than ten
(10) working days prior to performing maintenance that, in its reasonable
opinion, has a substantial likelihood of affecting WinStar's traffic for more
than 50 milliseconds. If Williams' planned activity is canceled or delayed,
Williams shall promptly notify WinStar and shall comply with the provisions of
the previous sentence to reschedule any delayed activity.

                                       48
<PAGE>

3.       Fiber and Cable

Williams shall correct or repair Cable discontinuity or damage. Williams shall
use commercially reasonable efforts to repair Cable traffic discontinuity within
the following times:

          Dispatch of personnel to problem area - immediately upon learning of
          discontinuity

          Maintenance employee's on site - within four (4) hours of learning of
          discontinuity

         Restoration of Cable continuity - continuity of at least one fiber
         shall be established within six (6) hours of learning of discontinuity;
         restoration shall continue until all in-service fibers are restored

Within twenty-four (24) hours after completion of an emergency repair, Williams
shall commence its planning for permanent repair, shall notify WinStar of such
plans, and shall implement such permanent repair within an appropriate time
thereafter.

Williams shall comply with the Cable splicing specifications as provided in
Exhibit C (entitled "Fiber Cable Splicing, Testing and Acceptance Standards").
Williams shall provide to WinStar any modifications to these specifications for
WinStar's approval, which shall not be unreasonably withheld, so long as the
modifications do not deviate from industry standards.

The demarcation point between the Cable and the facilities of WinStar or other
parties shall be at the Fiber distribution panel or (but only if Williams agrees
to establish such a connection) meet-me vault.

4.       Addition of Drop/Splice Points

WinStar shall have no right to access any Fibers within the Cable or to enter
any splice or Williams vault.

WinStar may request that Williams connect WinStar's Fibers with other
telecommunications facilities at WinStar's sole expense, at the Cable end points
or at Transmission Sites (each, a "Connecting Point"). Such request shall set
forth the splice location (which shall be at a demarcation point as set forth
above) and the work required to be performed.


                                       49
<PAGE>

WinStar shall notify Williams at least thirty (30) days in advance of the date
that it requests that a connection be completed. Williams shall use commercially
reasonable efforts to accommodate the request, but may restrict such work to the
planned system work periods set forth above.

Williams may decline to make a requested connection if Williams determines, in
its reasonable discretion, that there is a significant likelihood that (a)
WinStar's use of a proposed Connecting Point would cause a material and adverse
effect on the System or the use thereof; (b) use of a particular splice
locations will cause a significant technical impediment; or (c) the making or
existence of the connection presents an unreasonable risk of creating an
interruption of transmission.

WinStar shall have no right to establish any connection to the System other than
at the fiber distribution panels located at the end points or Transmission
Sites.

WinStar shall, prior to the requested connection date, provide a spur cable
adequate to reach the splice location with an additional length (minimum 25
meters) sufficient for Williams to splice into any Fibers at the fiber
distribution panel or meet-me vault. WinStar shall obtain the necessary rights
of way (or other rights, if required) for the spur cable and shall install and
maintain the spur cable beyond the demarcation point.

Williams may require WinStar to pay the costs of maintaining any splice point
that presents unusual problems of access for Williams. If WinStar has a
connection at a splice point and Williams requires access to WinStar Fibers for
inspection, maintenance, or repair purposes and Williams does not have physical
access to the Fibers to verify splicing specifications from Williams' fiber
distribution panel, WinStar shall promptly upon Williams' request provide a
trained and qualified technician at WinStar's fiber distribution panel with an
OTDR to assist Williams in performing such inspection, maintenance, or repair.

5.       Miscellaneous

Williams' maintenance employees shall be available for dispatch twenty-four (24)
hours a day, seven (7) days a week. Williams shall use commercially reasonable
efforts to have its first maintenance employee at the site requiring an
emergency maintenance activity within four (4) hours from the time of alarm
identification by Williams' NCC or notification by WinStar, whichever occurs
first. Emergency maintenance is defined as any service affecting situations
requiring an immediate response.

In performing its services hereunder, Williams shall take workmanlike care to
prevent impairment to the signal continuity and performance of the System. In
addition, Williams shall reasonably cooperate with WinStar in sharing
information and analyzing the disturbances regarding the cable and/or fiber
facilities.


                                       50
<PAGE>

Nothing contained herein shall make Williams responsible for WinStar's
equipment. If, however, Williams agrees to maintain WinStar electronic
equipment, WinStar shall provide equipment spares, vendor training and
documentation for each technician along the route when different vendor
equipment is used between Williams and WinStar.

Williams shall, at WinStar's request, provide WinStar an operations escalation
list for shall use in reporting and seeking redress of exceptions noted in
Williams' performance of Routine Maintenance and Non-Routine Maintenance.

                                       51

<PAGE>
                                                                       EXHIBIT J
                                                           INTENTIONALLY OMITTED

                                      51-A
<PAGE>

                                                                    Exhibit K

                                 Payment Terms 


1. Amount of Payment. WinStar shall pay Williams the Contract Price in
eighty-four (84) consecutive monthly installments of $7,656,577 each, due and
payable on the fifteenth (15th) day of each month, commencing February 15, 1999,
provided, however, that if any such date is not a day on which banks in New York
are open for business ("Business Day"), the payment due thereon shall be paid on
the next Business Day, and further provided, however that any such payment shall
be subject to adjustment as provided in Section 2 below.

2. Adjustment Events. Each monthly payment required by Section 1 above shall be
subject to adjustment pursuant to Sections 5.2(e), 6.4 and 10.4 of the
Agreement.

3.       Further Representation and Warranties.

     (a)  Security Matters. WinStar hereby represents and warrants (with defined
          terms having the meanings set forth in Section 7 below):

          (i)  Winstar has good and valid rights in and to the Collateral and
               has full power and authority and legal right to grant to the
               Secured Party the Security Interest in the Collateral pursuant
               hereto and to execute, deliver and perform its obligations in
               accordance with the terms of this Agreement, without the consent
               or approval of any other Person other than any consent or
               approval which has been obtained;

          (ii) The Security Interest (x) constitutes a legal and valid security
               interest in and to all of WinStar's rights in the Collateral
               securing the payment and performance of the Obligations and (y)
               upon the filing of appropriate UCC or other forms, will
 0             constitute a perfected security interest in and to all
               Collateral. The Security Interest is and shall be prior to any
               other Lien on any of the Collateral, except for Permitted
               Encumbrances; and

          (iii) WinStar has not filed or consented to the filing of any
               financing statement or analogous document under the Uniform
               Commercial Code or any other applicable laws covering any
               Collateral.

     (b)  Other Matters. WinStar hereby represents and warrants to Williams that
          (i) the representations and warranties of WinStar Network Expansion,
          LLC ("Borrower") and WinStar Communications, Inc. ("Parent") set forth
          in Article III of the Credit Agreement dated as of October 21, 1998
          (the "Lucent Credit Agreement"), among Borrower, Parent, the lenders
          party thereto, State Street Bank and Trust Company (as "Collateral
          Agent"), and Lucent Technologies, Inc. (as "Administrative Agent") are
          true and correct on the date of this Agreement with the same force and
          effect as if made on such date (or in the case of any representation
          and warranty that expressly relates to an earlier date, on and as of
          the earlier date) and (ii) that it has delivered to Williams a
          complete and correct copy of the Lucent Credit Agreement.

                                       52
<PAGE>

4. Events of Default. Until the Contract Price has been paid in full (except to
the extent the Payment Deductions have relieved WinStar of the obligation to pay
the Contract Price), notwithstanding the provisions of Article 21 of the
Agreement (except as to clause (h) below), each of the following shall
constitute an "Event of Default":
0
          (a)  WinStar shall fail to pay any portion of the Contract Price or
               the Exercise Price on the due date thereof (except to the extent
               the Payment Deductions have relieved WinStar of the obligation to
               pay the Contract Price or the Exercise Price);

          (b)  WinStar shall fail to pay any other amount in excess of $100,000
               due under the Agreement within 30 days after such amount has
               become due or any lesser amount within fifteen (15) days after
               receiving notice from Williams of such non-payment (except to the
               extent the Payment Deductions have relieved WinStar of the
               obligation to pay such amount);

          (c)  any representation or warranty made by WinStar in this Exhibit K
               or otherwise in this Agreement shall prove to have been incorrect
               when made in any respect which could reasonably be expected to
               have a material adverse effect upon Williams' ability to realize
               the benefits of the Agreement;

          (d)  there shall occur any breach (including without limitation any
               breach of any representation and warranty) by Parent under the
               Guarantee Agreement (as described below);

          (e)  an involuntary proceeding shall be commenced or an involuntary
               petition shall be filed seeking (i) liquidation, reorganization
               or other relief in respect of Parent or any of its Restricted
               Subsidiaries (as such term is defined in the Lucent Credit
               Agreement) or its debts, or of a substantial part of its assets,
               under any Federal, state or foreign bankruptcy, insolvency,
               receivership or similar law now or hereafter in effect or (ii)
               the appointment of a receiver, trustee, custodian, sequestrator,
               conservator or similar official for Parent or any of its
               Restricted Subsidiaries or for a substantial part of its assets,
               and, in any such case, such proceeding or petition shall continue
               undismissed for 60 days or an order or decree approving or
               ordering any of the foregoing shall be entered;

          (f)  Parent or any of its Restricted Subsidiaries shall (i)
               voluntarily commence any proceeding or file any petition seeking
               liquidation, reorganization or other relief under any Federal,
               state or foreign bankruptcy, insolvency, receivership or similar
               law now or hereafter in effect, (ii) consent to the institution
               of, or fail to contest in a timely and appropriate manner, any
               proceeding or petition described in clause (e) of this Section 4,
               (iii) apply for or consent to the appointment of a receiver,
               trustee, custodian, sequestrator, conservator, or similar
               official for Parent or any of its Restricted Subsidiaries or for
               a substantial part of its assets, (iv) file an answer admitting
               the material allegations of a petition filed against it in any
               such proceeding, (v) make a general assignment for the benefit of
               creditors or (vi) take any action for the purpose of effecting
               any of the foregoing;

                                       53
<PAGE>

          (g)  Parent or any of its Restricted Subsidiaries shall become unable,
               admit in writing its inability or fail generally to pay its debts
               as they become due;

          (h)  there shall occur any other event which entitles Williams to
               terminate this Agreement; or

          (i)  this Agreement shall cease, for any other reason, to be in full
               force and effect or WinStar shall so assert or the Lien (as
               defined below) created by this Agreement shall cease to be
               perfected or enforceable and of the same effect as to perfection
               and priority purported to be created hereunder.

5. Remedies. Upon any Event of Default, and at any time thereafter during the
continuance of such event, Williams may take any or all of the following actions
at the same or different times:

          (a)  cease to perform any of its obligations under the Agreement;

          (b)  terminate the Agreement; or

          (c)  seek to enforce its right to collect damages for breach of
               contract.

6.       Conditions Precedent.

          (a)  Prior to the first Acceptance Date, as a condition precedent to
               Williams obligations with respect to such Acceptance Date,
               WinStar shall cause the following actions to be taken:

               (i)  cause the Guarantee Agreement in the form attached hereto as
                    Annex A ("Guarantee") to be executed and delivered by
                    Parent;

               (ii) deliver to Williams an opinion of counsel reasonably
                    acceptable to Williams (which may be WinStar's General
                    Counsel), which opinion shall be satisfactory in form and
                    substance to Williams, to the effect set forth in Annex B
                    hereto; and

               (iii) deliver to Williams a certified copy of an amendment to the
                    Lucent Credit Agreement which permits the transactions
                    contemplated by this Agreement.

                                       54
<PAGE>

          (b)  Prior to each Acceptance Date (including the first), as a
               condition precedent to Williams' obligation on such Acceptance
               Date, WinStar shall take all actions required to perfect the
               security interests granted by this Agreement (whether or not the
               collateral is characterized as fixtures, equipment, contract
               rights, general intangibles or otherwise), using filings (when
               necessary) that are satisfactory in form and substance to
               Williams.

7.       Security Interest

          (a)  Definition of Certain Terms Used Herein. As used herein, the
               following terms shall have the following meanings:

          "Collateral" shall mean all of the following, whether now owned or
          existing or hereafter acquired or arising to the extent acquired by
          WinStar from Williams pursuant to this Agreement and used in
          connection with or arising out of the use of the Equipment: (i) all
          Equipment, (ii) all General Intangibles to the extent that a grant
          of a security interest therein to does not violate any agreement to
          which WinStar is now or may hereafter be subject, and (iii) all
   00     Proceeds.

         "Equipment" shall mean the following, to the extent acquired by WinStar
          from Williams pursuant to this Agreement: (i) all equipment, strands
          of optical fiber, and cable, or interests therein (ii) all tangible
          personal property similar to any of the foregoing, and (iii) all
          improvements, accessions or appurtenances thereto. The term Equipment
          shall include Fixtures.

         "Fixtures" shall mean all items of Equipment, whether now owned or
          hereafter acquired, of WinStar that become so related to particular
          real estate that an interest in them arises under any real estate law
          applicable thereto.

         "General Intangibles" shall mean the following, to the extent acquired
          by WinStar pursuant to this Agreement; (i) all "general intangibles"
          as such term is defined in the Section 9-106 of the UCC and (ii) all
          other intangible personal property of WinStar of every kind and nature
          now owned or heereafter acquired by WinStar, including WinStar's
          rights under this Agreement.

         "Lien" shall mean, with respect to any asset, (a) any mortgage, deed of
          trust, lien, pledge, hypothecation, encumbrance, charge or security
          interest in, on or of such asset, and (b) the interest of a vendor or
          a lessor under any conditional sale agreement, capital lease or title
          retention agreement (or any financing lease having substantially the
          same economic effect as any of the foregoing) relating to such asset.

          "Obligations" means all present and future monetary obligations of
          WinStar to Williams under this Agreement.

                                       55
<PAGE>

          "Permitted Encumbrances" shall have the meaning specified in the
          Lucent Credit Agreement.

         "Person" shall mean any natural person, corporation, limited liability
          company, trust, joint venture, association, company, partnership,
          governmental or regulatory authority or other entity.

         "Proceeds" shall mean any consideration received from the sale,
          exchange, license, lease or other disposition of any asset which
          constitutes Collateral, including any payment received from any
          insurer or other Person as a result of the destruction, loss, theft,
          damage or other involuntary conversion of whatever nature of any asset
          which constitutes Collateral.

          "Security Interest" shall have the meaning assigned to such term in
          paragraph (b) below.

         "Transaction Documents" shall mean this Agreement and the Guarantee .

          "Transactions" shall mean the execution, delivery, and performance by
          WinStar of each Transaction Document.

          "UCC" shall mean the Uniform Commercial Code as in effect in the State
          of New York or any other applicable jurisdiction.

     (b)  Security Interest. In order to effectuate the provisions of Section
          2.6 of the Agreement, as security for the payment or performance, as
          the case may be, in full of the Obligations, WinStar hereby bargains,
  0       sells, conveys, assigns, sets over, mortgages, pledges, hypothecates
          and transfers to Williams, its successors and assigns, and hereby
          grants to Williams, its successors and assigns, a security interest
          in, all of WinStar's right, title and interest in, to and under the
          Collateral (the "Security Interest"). Without limiting the foregoing,
          Williams is hereby authorized to file one or more financing statements
          (including fixture filings), continuation statements or other
          documents for the purpose of perfecting, confirming, continuing,
          enforcing or protecting the Security Interest granted by WinStar
          without the signature of WinStar, and naming WinStar as debtor and
          Williams as secured party.

     (c)  No Assumption of Liability. The Security Interest is granted as
          security only and shall not subject Williams to, or in any way alter
          or modify, any obligation or liability of WinStar with respect to or
          arising out of any of the Collateral.

     (d)  Protection of Security. WinStar shall, at its own cost and expense,
          take any and all actions necessary to defend title to the Collateral
          against all Persons and to defend the Security Interest of Williams in
          the Collateral and the priority thereof against any Lien.

                                       56
<PAGE>

     (e)  Further Assurances. WinStar shall, at its own expense, to execute,
          acknowledge, deliver and cause to be duly filed all such further
          instruments and documents (including Uniform Commercial Code financing
          statements in Collateral in which WinStar acquires an interest after
          the date hereof) and take all such actions as Williams may from time
          to time request to better assure, preserve, protect and perfect the
          Security Interest and the rights and remedies created hereby,
          including the payment of any fees and taxes required in connection
          with the execution and delivery of this Agreement, the granting of the
          Security Interest and the filing of any financing statements
          (including fixture filings) or other documents in connection herewith
          or therewith. WinStar agrees to take such action as may be requested
          by Williams to cause the Security Interest in Equipment to have
          priority pursuant to Sections 9-312(4) and 9-313 of the UCC, as
          applicable.

     (f)  Inspection and Verification. Williams and such Persons as Williams may
          reasonably designate shall have the right, on reasonable advance
          notice at WinStar's own cost and expense, to inspect the Collateral,
          all records related thereto (and to make extracts and copies from such
          records) and the premises upon which any of the Collateral is located,
          to discuss WinStar's affairs with the officers of WinStar and its
          independent accountants and to verify under reasonable procedures the
          validity, amount, quality, quantity, value, condition and status of,
          or any other matter relating to, the Collateral, including, in the
          case of Collateral in the possession of any third Person, by
          contacting the third Person possessing such Collateral for the purpose
          of making such a verification. Williams shall have the absolute right
          to share any information it gains from such inspection or verification
          with its agents and representatives.

     (g)  Taxes; Encumbrances. At its option, Williams may discharge past due
          taxes, assessments, charges, fees, Liens, security interests or other
          encumbrances at any time levied or placed on the Collateral and not
          permitted under the Transaction Documents and may pay for the
          maintenance and preservation of the Collateral to the extent WinStar
          fails to do so, and WinStar agrees to reimburse Williams on demand for
 0        any payment made or any expense incurred by Williams pursuant to the
          foregoing authorization; provided, however, that nothing in this
          Section 7 shall be interpreted as excusing WinStar from the
          performance of, or imposing any obligation on Williams to cure or
          perform, any covenants or other promises of WinStar with respect to
          taxes, assessments, charges, fees, Liens, security interests or other
          encumbrances.

     (h)  Continuing Obligations of WinStar. WinStar shall remain liable to
          observe and perform all the conditions and obligations to be observed
          and performed by it under each contract, agreement or instrument
          relating to the Collateral, all in accordance with the terms and
          conditions thereof, and WinStar agrees to indemnify and hold harmless
          Williams and Williams' Affiliates from and against any and all
          liability for such performance.

     (i)  Use and Disposition of Collateral. Except as otherwise permitted by
          this Agreement, WinStar shall not make or permit to be made an
          assignment, pledge or hypothecation of the Collateral or grant any
          other Lien in respect of the Collateral, and WinStar shall not sell,
          convey, lease, assign, transfer or otherwise dispose of any
          Collateral, except in any such case in the ordinary course of
          business.

                                       57

<PAGE>

     (j)  Power of Attorney. Williams shall have the right, as the true and
          lawful agent and attorney-in-fact of WinStar, with power of
          substitution for WinStar and in WinStar's name or otherwise, for the
          use and benefit of Williams, upon the occurrence and during the
          continuance of an Event of Default (a) to receive, endorse, assign
          and/or deliver any and all notes, acceptances, checks, drafts, money
          orders or other evidences of payment relating to the Collateral or any
          part thereof; (b) to demand, collect, receive payment of, give receipt
          for and give discharges and releases of all or any of the Collateral;
          (c) to commence and prosecute any and all suits, actions or
          proceedings at law or in equity in any court of competent jurisdiction
          to collect or otherwise realize on all or any of the Collateral or to
          enforce any rights in respect of any Collateral; (d) to settle,
          compromise, compound, adjust or defend any actions, suits or
          proceedings relating to all or any of the Collateral; and (e) to use,
          sell, assign, transfer, pledge, make any agreement with respect to or
          otherwise deal with all or any of the Collateral, and to do all other
          acts and things necessary to carry out the purposes of this Agreement,
          as fully and completely as though Williams were the absolute owner of
          the Collateral for all purposes; provided, however, that nothing
          herein contained shall be construed as requiring or obligating
          Williams to make any commitment or to make any inquiry as to the
          nature or sufficiency of any payment received by Williams, or to
          present or file any claim or notice, or to take any action with
          respect to the Collateral or any part thereof or the moneys due or to
          become due in respect thereof or any property covered thereby, and no
          action taken or omitted to be taken by Williams with respect to the
          Collateral or any part thereof shall give rise to any defense,
          counterclaim or offset in favor of WinStar or to any claim or action
          against Williams. It is understood and agreed that the appointment of
          Williams as the agent and attorney-in-fact of WinStar for the purposes
          set forth above is coupled with an interest and is irrevocable. The
          provisions of this Section shall in no event relieve WinStar of any of
          its obligations hereunder with respect to the Collateral or any part
          thereof or impose any obligation on Williams to proceed in any
          particular manner with respect to the Collateral or any part thereof,
          or in any way limit the exercise by Williams of any other or further
          right which it may have on the date of this Agreement or hereafter,
          whether hereunder, under any other Transaction Document, by law or
          otherwise.

     (k)  Remedies upon Default.

         (i) Upon the occurrence and during the continuance of an Event of
          Default, Williams shall have the right with or without legal process
          and with or without previous notice or demand for performance, to take
          possession and/or control of the Collateral or any part thereof (at
          the same or different times) and without liability for trespass to
          enter any premises where the Collateral or any part thereof may be
          located for the purpose of taking possession of or removing the
          Collateral and, generally, to exercise any and all rights afforded to
          a secured party under the UCC or other applicable law. Without
          limiting the generality of the foregoing, WinStar agrees that Williams
          shall have the right, subject to the mandatory requirements of
          applicable law, to sell or otherwise dispose of all or any part of the
          Collateral, at public or private sale for cash, upon credit or for
          future delivery as Williams shall deem appropriate. Upon consummation
          of any such sale Williams shall have the right to assign, transfer and
          deliver to the purchaser or purchasers thereof the Collateral so sold.
          Each such purchaser at any such sale shall hold the property sold
          absolutely, free from any claim or right on the part of WinStar, and
          WinStar hereby waives (to the extent permitted by law) all rights of
          redemption, marshalling, stay and appraisal which WinStar now has or
          may at any time in the future have under any rule of law or statute
          now existing or hereafter enacted.
0

                                       58
<PAGE>

         (ii) Williams shall give WinStar 10 days' written notice (which WinStar
          agrees is reasonable notice within the meaning of Section 9-504(3) of
          the UCC or its equivalent in other jurisdictions) of Williams'
          intention to make any sale of Collateral. Such notice, in the case of
          a public sale, shall state the time and place for such sale. Any such
          public sale shall be held at such time or times within ordinary
          business hours and at such place or places as Williams may fix and
          state in the notice of such public sale. At any such sale, the
          Collateral, or portion thereof, to be sold may be sold in one lot as
          an entirety or in separate parcels, as Williams may (in its sole and
          absolute discretion) determine. Williams shall not be obligated to
          make any sale of any Collateral if it shall determine not to do so,
          regardless of the fact that notice of sale of such Collateral shall
          have been given. Williams may, without notice or publication, adjourn
          any public or private sale or cause the same to be adjourned from time
          to time by announcement at the time and place fixed for sale, and such
          sale may, without further notice, be made at the time and place to
          which the same was so adjourned. In case any sale of all or any part
          of the Collateral is made on credit or for future delivery, the
          Collateral so sold may be retained by Williams until the sale price is
          paid by the purchaser or purchasers thereof, but Williams shall not
          incur any liability in case any such purchaser or purchasers shall
          fail to take up and pay for the Collateral so sold and, in case of any
          such failure, such Collateral may be sold again upon like notice. At
          any public (or, to the extent permitted by law, private) sale made
          pursuant to this Section, Williams may bid for or purchase, free (to
  0       the extent permitted by law) from any right of redemption, stay,
          valuation or appraisal on the part of WinStar (all said rights being
          also hereby waived and released to the extent permitted by law), the
          Collateral or any part thereof offered for sale and may make payment
          on account thereof by using any Obligation then due and payable to
          Williams from WinStar as a credit against the purchase price and
          Williams may, upon compliance with the terms of sale, hold, retain and
          dispose of such property without further accountability to WinStar
          therefor. For purposes hereof, a written agreement to purchase the
          Collateral or any portion thereof shall be treated as a sale thereof,
          Williams shall be free to carry out such sale pursuant to such
          agreement and WinStar shall not be entitled to the return of the
          Collateral or any portion thereof subject thereto, notwithstanding the
          fact that after Williams shall have entered into such an agreement all
          Events of Default shall have been remedied and the Obligations paid in
          full. As an alternative to exercising the power of sale herein
          conferred upon it, Williams may proceed by a suit or suits at law or
          in equity to foreclose this Agreement and to sell the Collateral or
          any portion thereof pursuant to a judgment or decree of a court or
          courts having competent jurisdiction or pursuant to a proceeding by a
          court-appointed receiver.

     (l)  Application of Proceeds. Williams shall apply the proceeds of any
          collection or sale of the Collateral, as well as any Collateral
          consisting of cash, as follows:

                                       59
<PAGE>

       FIRST, to the payment of all costs and expenses incurred by Williams in
          connection with such collection or sale or otherwise in connection
 0        with this Agreement or any of the Obligations, including all court
          costs and the fees and expenses of its agents and legal counsel, the
          repayment of all advances made by Williams hereunder or under any
          other Transaction Document on behalf of WinStar and any other costs or
          expenses incurred in connection with the exercise of any right or
          remedy hereunder or under any other Transaction Document;

         SECOND, to the payment in full of the Obligations; and

       THIRD, to WinStar, its successors or assigns, or as a court of competent
          jurisdiction may otherwise direct.

         Williams shall have absolute discretion as to the time of application
          of any such proceeds, moneys or balances in accordance with this
          Agreement. Upon any sale of the Collateral by Williams (including
          pursuant to a power of sale granted by statute or under a judicial
          proceeding), the receipt of Williams or of the officer making the sale
          shall be a sufficient discharge to the purchaser or purchasers of the
          Collateral so sold and such purchaser or purchasers shall not be
          obligated to see to the application of any part of the purchase money
          paid over to Williams or such officer or be answerable in any way for
          the misapplication thereof.

     (m)  Williams' Fees and Expenses; Indemnification.

          (i)  WinStar agrees to pay upon demand to Williams the amount of any
               and all reasonable expenses (other than those incurred in
               connection with the negotiation and preparation of this
               Agreement), including the reasonable fees and expenses of its
               counsel and of any experts or agents, which Williams may incur in
               connection with (a) the administration of this Section 7, (b) the
0              custody or preservation of, or the sale of, collection from or
               other realization upon any of the Collateral, (c) the exercise,
               enforcement or protection of any of the rights of Williams or
               under Section 7 (d) the failure of WinStar to perform or observe
               any of the provisions of this Section 7.

          (ii) WinStar agrees to indemnify Williams against, and hold it
               harmless from, all stamp, documentary and other taxes, levies or
               charges payable in respect of the grant of the Security Interest.

          (iii) The provisions of this Section shall remain operative and in
               full force and effect regardless of the termination of this
               Agreement or any other Transaction Document.

                                       60
<PAGE>

                                                         Annex A To Exhibit K

                               GUARANTEE AGREEMENT


         GUARANTEE  AGREEMENT  (this  "Agreement")  dated as of  December ___, 
1998, among WINSTAR COMMUNICATIONS, INC., a Delaware corporation ("Guarantor"),
and WILLIAMS COMMUNICATIONS, INC. ("Williams").

         Reference is made to the IRU Agreement dated as of December 17, 1998
(as amended or modified from time to time, the "IRU Agreement"), between WinStar
Wireless, Inc., a Delaware corporation ("Wireless"), and Williams. Capitalized
terms used herein and not defined herein shall have the meanings assigned to
such terms in the IRU Agreement.

         Wireless is a wholly-owned subsidiary of Guarantor. Guarantor
acknowledges that it will derive substantial direct and indirect benefit from
the IRU Agreement. The obligations of Williams under the IRU Agreement are
conditioned on, among other things, the execution and delivery by Guarantor of a
Guarantee Agreement in the form hereof. As consideration therefor and in order
to induce Williams to enter into and perform its obligations under the IRU
Agreement, Guarantor is willing to execute this Agreement.

         Accordingly, the parties hereto agree as follows:

                                    ARTICLE I

                                    Guarantee

         SECTION 1.01 Guarantee. Guarantor unconditionally guarantees, as a
primary obligor and not merely as a surety, (a) the due and punctual payment of
all monetary obligations, including fees, costs, expenses and indemnities,
whether primary, secondary, direct, contingent, fixed or otherwise (including
monetary obligations incurred during the pendency of any bankruptcy, insolvency,
receivership or other similar proceeding, regardless of whether allowed or
allowable in such proceeding), of Wireless under the IRU Agreement and (b) the
due and punctual performance of all covenants, agreements, obligations and
liabilities of Wireless under or pursuant to the IRU Agreement (all the monetary
and other obligations referred to in the preceding clauses (a) and (b) being
collectively called the "Obligations"). Guarantor further agrees that the
Obligations may be extended or renewed, in whole or in part, without notice to
or further assent from it, and that it will remain bound upon its guarantee
notwithstanding any extension or renewal of any Obligation.

                                       61
<PAGE>

         SECTION 1.02 Obligations Not Waived. To the fullest extent permitted by
applicable law, Guarantor waives presentment to, demand of payment from and
protest to Wireless of any of the Obligations, and also waives notice of
acceptance of its guarantee and notice of protest for nonpayment. To the fullest
extent permitted by applicable law, the obligations of Guarantor hereunder shall
not be affected by (a) the failure of Williams to assert any claim or demand or
to enforce or exercise any right or remedy against Wireless or Guarantor under
the provisions of the IRU Agreement or otherwise, (b) any rescission, waiver,
amendment or modification of, or any release from any of the terms or provisions
of this Agreement or any other agreement, or (c) the failure to perfect any
security interest in, or the release of, any of the security held by Williams.

         SECTION 1.03 Security. Guarantor authorizes Williams to (a) take and
hold security given for the payment of the Obligations and exchange, enforce,
waive and release any such security, (b) apply such security and direct the
order or manner of sale thereof as they in their sole discretion may determine
and (c) release or substitute any one or more endorsees, other guarantors or
other obligors.

         SECTION 1.04 Guarantee of Payment. Guarantor further agrees that its
guarantee constitutes a guarantee of payment when due and not of collection, and
waives any right to require that any resort be had by Williams to any of the
security held for payment of the Obligations.

         SECTION 1.05 No Discharge or Diminishment of Guarantee. The obligations
of Guarantor hereunder shall not be subject to any reduction, limitation,
impairment or termination for any reason (other than the indefeasible payment in
full in cash of the Obligations), including any claim of waiver, release,
surrender, alteration or compromise of any of the Obligations, and shall not be
subject to any defense or setoff, counterclaim, recoupment or termination
whatsoever by reason of the invalidity, illegality or unenforceability of the
Obligations or otherwise. Without limiting the generality of the foregoing, the
obligations of Guarantor hereunder shall not be discharged or impaired or
otherwise affected by the failure of Williams to assert any claim or demand or
to enforce any remedy under the IRU Agreement or any other agreement, by any
waiver or modification of any provision of any thereof, by any default, failure
or delay, willful or otherwise, in the performance of the Obligations, or by any
other act or omission that may or might in any manner or to any extent vary the
risk of Guarantor or that would otherwise operate as a discharge of Guarantor as
a matter of law or equity (other than the indefeasible payment in full in cash
of all the Obligations).

         SECTION 1.06 Other Matters. Williams may, at its election, foreclose on
any security held by it by one or more judicial or nonjudicial sales, accept an
assignment of any such security in lieu of foreclosure, compromise or adjust any
part of the Obligations, make any other accommodation with Wireless or any other
guarantor or exercise any other right or remedy available to them against
Wireless or any other guarantor, without affecting or impairing in any way the
liability of Guarantor hereunder except to the extent the Obligations have been
fully, finally and indefeasibly paid in cash. To the fullest extent permitted by
applicable law, Guarantor waives any defense arising out of any such election
even though such election operates, pursuant to applicable law, to impair or to
extinguish any right of reimbursement or subrogation or other right or remedy of
Guarantor against Wireless or any other guarantor, as the case may be, or any
security.

                                       63
<PAGE>

         SECTION 1.07 Limit of Liability. The obligations of Guarantor hereunder
shall be limited to an aggregate amount equal to the largest amount that would
not render its obligations hereunder subject to avoidance under Section 548 of
the United States Bankruptcy Code or any comparable provisions of applicable
state law.


                                   ARTICLE II

                                  Subordination

         SECTION 2.01 Subordination. Parent hereby agrees that all the
Subordinated Obligations of Wireless owed to Parent are hereby expressly
subordinated, to the extent and in the manner set forth in this Article II, to
the prior payment in full in cash of all Senior Obligations of Wireless in
accordance with the terms thereof.

         As used herein:

         "Senior Creditors" means Williams and its successors and assigns.

         "Senior Obligations" of any means, the Obligations.

         "Subordinated Obligations" of Wireless means all monetary obligations
and other liabilities of Wireless at any time owing to Parent (including any
such obligations or other liabilities owing to any other Person for the direct
or indirect benefit of Parent), including all rights of Parent against Wireless
arising by way of right of subrogation, contribution, reimbursement, indemnity
or otherwise.

         SECTION 2.02 Dissolution or Insolvency. Parent agrees that upon any
distribution of the assets of Wireless or upon any dissolution, winding up,
liquidation or reorganization of Wireless, whether in bankruptcy, insolvency,
reorganization, arrangement or receivership proceedings or otherwise, or upon
any assignment for the benefit of creditors or any other marshaling of the
assets and liabilities of Wireless:

     (a)  the Senior Creditors of Wireless shall first be entitled to receive
          payment in full in a cash of the Senior Obligations in accordance with
          the terms of such Senior Obligations before Parent shall be entitled
          to receive any payment on account of the Subordinated Obligations of
          Wireless, whether as principal, interest or otherwise; and

     (b)  any payment by, or distribution of the assets of, Wireless of any kind
          or character, whether in cash, property or securities, received by or
          on behalf of Parent shall be held in trust for the benefit of, and
          shall be paid over to, the Senior Creditors of Wireless to the extent
          necessary to make payment in full in cash of all Senior Obligations
          remaining unpaid, after giving effect to any concurrent payment or
          distribution to the Senior Creditors in respect of the Senior
          Obligations.


                                       63
<PAGE>

         SECTION 2.03 Other Creditors. Nothing contained in this Agreement is
intended to or shall impair, as between and among Wireless, its creditors (other
than its Senior Creditors) and Parent, the Obligations of Wireless to pay to
Parent the Subordinated Obligations as and when the same shall become due and
payable in accordance with the terms thereof, or affect the relative rights of
Parent and the other creditors of Wireless (other than its Senior Creditors).

         SECTION 2.04 Proofs of Claims. In the event of any dissolution, winding
up, liquidation or reorganization of Wireless, whether in bankruptcy,
insolvency, reorganization, arrangement or receivership proceedings or
otherwise, or any assignment for the benefit of creditors or any other
marshaling of the assets and liabilities of Wireless, Parent agrees to file
proofs of claim for the Subordinated Obligations owed to it upon demand by
Williams, in default of which Williams is hereby irrevocably authorized so to
file in order to effectuate the provisions hereof. This Section shall not be
construed to permit Parent to retain any payment received by it in respect of a
Subordinated Obligation that Parent is not entitled to retain under any other
provision of the Agreement.

         SECTION 2.05 No Waiver. No right of any Senior Creditor to enforce this
Agreement shall at any time or in any way be prejudiced or impaired by any act
or failure to act on the part of any Senior Creditor, Parent or Wireless, or by
any noncompliance by Parent or Wireless with the terms, provisions and covenants
contained herein, and the Senior Creditors are hereby expressly authorized to
extend, renew, increase, decrease, modify or amend the terms of the Senior
Obligations or any security therefor, and to release, sell or exchange any such
security and otherwise deal freely with Wireless, all without notice to or
consent of Parent and without affecting the liabilities and obligations of the
parties hereto.

         SECTION 2.06. Transfer of Subordinated Obligations. Parent agrees that
it will not sell, assign, transfer or otherwise dispose of all or any part of
the Subordinated Obligations owed to it unless the Person to whom such sale,
assignment, transfer or disposition is made shall acknowledge in writing
(delivered to Williams) that it shall be bound by the terms of this Agreement,
including the terms of this Section 2.06, as though named herein as a
Subordinated Creditor.

         SECTION 2.07.  Obligations  Hereunder  Not  Affected.  (a) All rights 
and  interests of the Senior  Creditors  hereunder,  and all agreements and
obligations of Parent hereunder, shall remain in full force and effect
irrespective of:

          (i)  any lack of validity or enforceability of the IRU Agreement;

          (ii) any change in the time, manner or place of payment of, or in any
               other term of, all or any of the Senior Obligations, or any other
               amendment or waiver of or consent to departure from the IRU
               Agreement;

          (iii) any exchange, release or nonperfection of any security interest
               in any collateral, or any release or amendment or waiver of or
               consent to departure from any guarantee, in respect of all or any
               of the Senior Obligations; or


                                       64
<PAGE>

          (iv) any other circumstance that might otherwise constitute a defense
               available to, or a discharge of, Wireless in respect of its
               Senior Obligations or of Parent in respect of this Agreement.

     (b)  Parent hereby authorizes the Senior Creditors, without notice or
demand and without affecting or impairing any of the obligations of Parent
hereunder, from time to time to (i) renew, compromise, extend, increase,
accelerate or otherwise change the time for payment of, or otherwise change the
terms of, the Senior Obligations or any part thereof and (ii) exercise or
refrain from exercising any rights against Parent or any other Person.


                                   ARTICLE III

                                  Miscellaneous

         SECTION 3.01 Representations and Warranties. Guarantor represents and
warrants that:

         (a) Organization; Powers. It is a corporation duly organized, validly
existing and in good standing under the laws of the jurisdiction of its
organization, has all requisite corporate power and authority to carry on its
business as now conducted and, except where the failure to do so, individually
or in the aggregate, could not reasonably be expected to have a material adverse
effect on its business, operations or condition (financial or otherwise), is
qualified to do business in, and is in good standing in, every jurisdiction
where such qualification is required.

         (b) Authorization; Enforceability. The transactions contemplated hereby
are within its corporate power and have been duly authorized by all necessary
corporate action. This Agreement has been duly executed and delivered by it and
constitutes a legal, valid and binding obligation of it, enforceable in
accordance with its terms, subject to applicable bankruptcy, insolvency,
reorganization, moratorium or other laws affecting creditors' rights generally
and subject to general principles of equity, regardless of whether considered in
a proceeding in equity or at law.

         (c) Governmental Approvals; No Conflicts. The transactions contemplated
hereby (i) do not require any consent or approval of, registration or filing
with, or any other action by, any governmental or regulatory authority, (ii)
will not violate any applicable law or regulation or its charter, by-laws or
other organizational documents of it or any order of any governmental or
regulatory authority, (iii) will not violate or result in a default under any
indenture, agreement or other instrument binding upon it or its assets, or give
rise to a right thereunder to require any payment to be made by it, and (iv)
will not result in the creation or imposition of any lien on any of its assets.

                                       65
<PAGE>

         SECTION 3.02 Information. Guarantor assumes all responsibility for
being and keeping itself informed of Wireless' financial condition and assets,
and of all other circumstances bearing upon the risk of nonpayment of the
Obligations and the nature, scope and extent of the risks that Guarantor assumes
and incurs hereunder, and agrees that Williams will not have any duty to advise
Guarantor of any information known to it or regarding such circumstances or
risks.

         SECTION 3.03 Termination of this Agreement and the Guarantees. This
Agreement and the Guarantee made hereunder shall terminate when all the
Obligations have been indefeasibly paid in full and Williams has no further
commitments under the IRU Agreement and shall continue to be effective or be
reinstated, as the case may be, if at any time payment, or any part thereof, of
any Obligation is rescinded or must otherwise be restored by Williams upon the
bankruptcy or reorganization of Wireless, Guarantor or otherwise.

         SECTION 3.04 Binding Effect; Several Agreement; Assignments. Whenever
in this Agreement any of the parties hereto is referred to, such reference shall
be deemed to include the successors and assigns of such party; and all
covenants, promises and agreements by or on behalf of each party hereto that are
contained in this Agreement shall bind and inure to the benefit of each party
hereto and their respective successors and assigns. This Agreement shall become
effective as to Williams and Guarantor when a counterpart hereof executed on
behalf of such party shall have been delivered to Williams, and a counterpart
hereof shall have been executed on behalf of Williams, and thereafter shall be
binding upon such party and Williams and their respective successors and
assigns, and shall inure to the benefit of such party and Williams, and their
respective successors and assigns, except that Guarantor shall not have the
right to assign its rights or obligations hereunder or any interest herein (and
any such attempted assignment shall be void).

         SECTION 3.05 Waivers; Amendment. (a) No failure or delay of Williams in
exercising any power or right hereunder shall operate as a waiver thereof, nor
shall any single or partial exercise of any such right or power, or any
abandonment or discontinuance of steps to enforce such a right or power,
preclude any other or further exercise thereof or the exercise of any other
right or power. The rights and remedies of Williams hereunder and under the IRU
Agreement are cumulative and are not exclusive of any rights or remedies that
they would otherwise have. No waiver of any provision of this Agreement or
consent to any departure by Guarantor therefrom shall in any event be effective
unless the same shall be permitted by paragraph (b) below, and then such waiver
or consent shall be effective only in the specific instance and for the purpose
for which given. No notice or demand on Guarantor in any case shall entitle
Guarantor to any other or further notice or demand in similar or other
circumstances.

         (b) Neither this Agreement nor any provision hereof may be waived,
amended or modified except pursuant to a written agreement entered into between
the parties.


         SECTION 3.06  Governing  Law. THIS  AGREEMENT  SHALL BE GOVERNED BY, 
AND CONSTRUED IN ACCORDANCE  WITH,  THE LAWS OF THE STATE OF NEW YORK.


                                       66
<PAGE>

         SECTION 3.07 Notices. All communications and notices hereunder shall be
in writing and given as provided in Article XIII of the IRU Agreement, provided,
however, that all communications and notices hereunder to Guarantor shall be
given to it at:

                       WinStar Communications, Inc.
                       Attn:  General Counsel
                              230 Park Avenue
                              New York, New York   10169
                              Facsimile No: (212) ______________

or at such other address as may be designated in writing to Williams.

         SECTION 3.08 Survival of Agreement; Severability. (a) All covenants,
agreements, representations and warranties made by Guarantor herein and in the
certificates or other instruments prepared or delivered in connection with or
pursuant to this Agreement or the IRU Agreement shall be considered to have been
relied upon by Williams, regardless of any investigation made by Williams, and
shall continue in full force and effect as long as any of the Obligations is
outstanding and unpaid and as long as the IRU Agreement has not been terminated.

         (b) In the event any one or more of the provisions contained in this
Agreement or in the IRU Agreement should be held invalid, illegal or
unenforceable in any respect, the validity, legality and enforceability of the
remaining provisions contained herein and therein shall not in any way be
affected or impaired thereby (it being understood that the invalidity of a
particular provision in a particular jurisdiction shall not in and of itself
affect the validity of such provision in any other jurisdiction). The parties
shall endeavor in good faith negotiations to replace the invalid, illegal or
unenforceable provisions with valid provisions the economic effect of which
comes as close as possible to that of the invalid, illegal or unenforceable
provisions.


         SECTION 3.09 Counterparts. This Agreement may be executed in
counterparts, each of which shall constitute an original, but all of which when
taken together shall constitute a single contract, and shall become effective as
provided in Section 3.04. Delivery of an executed signature page to this
Agreement by facsimile transmission shall be as effective as delivery of a
manually executed counterpart of this Agreement.

         SECTION 3.10 Rules of Interpretation. The rules of interpretation
specified in Article XXIII of the IRU Agreement shall be applicable to this
Agreement.

         SECTION 3.11 Jurisdiction; Consent to Service of Process. (a) Guarantor
hereby irrevocably and unconditionally submits, for itself and its property, to
the nonexclusive jurisdiction of any New York State court or Federal court of
the United States of America sitting in New York City, and any appellate court
from any thereof, in any action or proceeding arising out of or relating to this
Agreement, or for recognition or enforcement of any judgment, and each of the


                                       67
<PAGE>
parties hereto hereby irrevocably and unconditionally agrees that all claims in
respect of any such action or proceeding may be heard and determined in such New
York State or, to the extent permitted by law, in such Federal court. Each of
the parties hereto agrees that a final judgment in any such action or proceeding
shall be conclusive and may be enforced in other jurisdictions by suit on the
judgment or in any other manner provided by law. Nothing in this Agreement shall
affect any right that Williams may otherwise have to bring any action or
proceeding relating to this Agreement or the other Transaction Documents against
Guarantor or its properties in the courts of any jurisdiction.

         (b) Guarantor hereby irrevocably and unconditionally waives, to the
fullest extent it may legally and effectively do so, any objection that it may
now or hereafter have to the laying of venue of any suit, action or proceeding
arising out of or relating to this Agreement in any New York State or Federal
court. Each of the parties hereto hereby irrevocably waives, to the fullest
extent permitted by law, the defense of an inconvenient forum to the maintenance
of such action or proceeding in any such court.


         (c) Each party to this Agreement irrevocably consents to service of
process in the manner provided for notices in Section 3.07. Nothing in this
Agreement will affect the right of any party to this Agreement to serve process
in any other manner permitted by law.


         SECTION 3.12 Waiver of Jury Trial. EACH PARTY HERETO HEREBY WAIVES, TO
THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY RIGHT IT MAY HAVE TO A TRIAL
BY JURY IN RESPECT OF ANY LITIGATION DIRECTLY OR INDIRECTLY ARISING OUT OF,
UNDER OR IN CONNECTION WITH THIS AGREEMENT OR THE OTHER TRANSACTION DOCUMENTS.
EACH PARTY HERETO (A) CERTIFIES THAT NO REPRESENTATIVE, AGENT OR ATTORNEY OF ANY
OTHER PARTY HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PARTY WOULD
NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER AND (B)
ACKNOWLEDGES THAT IT AND THE OTHER PARTIES HERETO HAVE BEEN INDUCED TO ENTER
INTO THIS AGREEMENT AND THE OTHER TRANSACTION DOCUMENTS, AS APPLICABLE, BY,
AMONG OTHER THINGS, THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION 3.12.

IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement as of
the day and year first above written.


WILLIAMS COMMUNICATIONS, INC.

By  ______________________________
Name:
Title:


                                       68
<PAGE>

WINSTAR COMMUNICATIONS, INC.,

By  ___________________________________
Name:
Title:


                                       69
<PAGE>


                                                        Annex B to Exhibit K



         Organization; Powers. WinStar and Parent is each a corporation duly
organized, validly existing and in good standing under the laws of the
jurisdiction of its organization and has all requisite corporate power and
authority to carry on its business as now conducted.

         Authorization; Enforceability. (i) The obligations to be performed by
WinStar under the IRU Agreement are within WinStar's corporate power and have
been duly authorized by all necessary corporate action. This Agreement has been
duly executed and delivered by WinStar and constitutes a legal, valid and
binding obligation of WinStar, enforceable in accordance with its terms, subject
to applicable bankruptcy, insolvency, reorganization, moratorium or other laws
affecting creditors' rights generally and subject to general principles of
equity, regardless of whether considered in a proceeding in equity or at law.

         (ii) The obligations to be performed by Parent under the Guarantee
Agreement are within Parent's corporate power and have been duly authorized by
all necessary corporate action. Such Agreement has been duly executed and
delivered by Parent and constitutes a legal, valid and binding obligation of
Parent, enforceable in accordance with its terms, subject to applicable
bankruptcy, insolvency, reorganization, moratorium or other laws affecting
creditors' rights generally and subject to general principles of equity,
regardless of whether considered in a proceeding in equity or at law.

         Governmental Approvals; No Conflicts. The transactions contemplated by
this Agreement (a) will not violate the charter, by-laws or other organizational
documents of WinStar or Parent, (b) will not violate or result in a default
under any indenture, agreement or other instrument known to us (including all
agreements filed as exhibits to filings by Parent with the Securities and
Exchange Commission) binding upon WinStar or Parent or its assets, or give rise
to a right thereunder to require any payment to be made by WinStar or Parent,
and (c) will not result in the creation or imposition of any lien on any asset
of WinStar or Parent, except liens created under this Agreement.





                                       70


<PAGE>
                                                                       EXHIBIT L
                                                           INTENTIONALLY OMITTED
                                      70-A
<PAGE>
                                                                       EXHIBIT M
    
                                                       INTENTIONALLY OMITTED
                                      70-B
<PAGE>
                                                                       EXHIBIT N
                                                           INTENTIONALLY OMITTED
                                      70-C
<PAGE>
                                    Exhibit O
Williams Network POP List
<TABLE>
<CAPTION>
  ================================================================================================================================
  Williams Network Onnet City List             X indicates InService
                                                                                            Horizontal
                                POP Sq.                                         Vertical    Coordin-    NPA/         Local Access
         City               St  Ft.         Address            LATA  CLLI CODE  Coordinate    ate       NXX          Vendor
  =================================================================================================================================
<S>                       <C>    <C>                            <C>  <C>        <C>         <C>         <C>        <C> 
 1      Albany             NY    5,000 194 Washington Avenue 
                                        Albany, NY 12210        134  ALBYNY1W       4640      1630     518/436       NYNEX MFS BS
         --------------------------------------------------------------------------------------------------------------------------
  2   x  Atlanta            GA   10,000 374 Dekalb Avenue 
                                        Atlanta, GA 30312       438  ATLNGA1W       7259      2084     404/688       MFS BST
         --------------------------------------------------------------------------------------------------------------------------
  3      Baltimore          MD   10,000 200 North Howard Street                                                      BELLATLANTIC
                                        Baltimore, MD 21201     228  BLTMMD1W       5511      1574      410/962      ESPIRE
         --------------------------------------------------------------------------------------------------------------------------
  4   x  Baton Rouge        LA    3,000 445 N Boulevard 
                                        Suite 500 
                                        Baton Rouge, LA 70802   492  BTRGLA1W       5475      2874      504/343      BST ACSI
         --------------------------------------------------------------------------------------------------------------------------
  5   x  Birmingham         AL    3,408 2001 Park Place North 
                                        Suite 102 
                                        Birmingham, AL 35203    476  BRHMAL1W       7518      2446      205/322      BST ACSI
         --------------------------------------------------------------------------------------------------------------------------
  6      Buffalo            NY    5,000 325 Delaware Avenue 
                                        2nd Fl.                                                                      BELLATLANTIC
                                        Buffalo, NY 14202       140  BFLONY1W       5076      2327      716/854      HYPERION
         --------------------------------------------------------------------------------------------------------------------------
  7   x  Charlotte          NC    9,000 112 N Meyers St. 
                                        Charlotte, NC 28202     422  CHRLNC2W       5657      1598       704/347     BST PW
         --------------------------------------------------------------------------------------------------------------------------
  8   x  Chicago            IL    5,000 600 South Federal 
                                        5th Floor 
                                        Chicago, IL 60605       358  CHCGIL1W       5987       2424       312/986   MFS AMERITECH
         --------------------------------------------------------------------------------------------------------------------------
  9      Cleveland          OH    2,362 The Keith Building 
                                        1521 Euclid Ave Ste 522                                                     MFS
                                        Cleveland, OH           320  CLEVOH1W       5576       2544       215/687   AMERITECH CS
         --------------------------------------------------------------------------------------------------------------------------
  10  x  Dallas             TX    5,353 One Main Place 
                                        1201 Main St Ste C-112 
                                        Dallas, TX 75202        552  DLLSTXRID1W    8437       4035       214/742   ACSI MFS SWB
         --------------------------------------------------------------------------------------------------------------------------
  11     Daytona Beach      FL   10,000 111 N. Seagrave 
                                        Daytona Beach, FL 32114 456  DYBHFL1W       7803       1036       904/252   BST
         --------------------------------------------------------------------------------------------------------------------------
  12     Ft. Lauderdale     FL   10,000 SW Corner of 2nd St 
                                        NW & 2nd Ave NW         460  FTKDFK1W       8281.14    558.34               BST
         --------------------------------------------------------------------------------------------------------------------------
  13  x  Greensboro         NC    5,394 South Elm Center 201-E 
                                        Creek Ridge Road 
                                        Greensboro, NC 27406    424  GNBONC1W       6402       1639       336/275   BST TW
         --------------------------------------------------------------------------------------------------------------------------
  14  x  Houston           TX     5,000 1124 Hardy Street 
                                        Houston, TX 77020       560  HSTNTX1W       8936       3536       713/225   TW SWB
         --------------------------------------------------------------------------------------------------------------------------
  15  x  Indianapolis      IN     5,723 720 Kentucky Avenue 
                                        Suite 2 
                                        Indianapolis, IN        336  IPLSHN1W       6272       2992       317/916   TW AMT
         --------------------------------------------------------------------------------------------------------------------------
  16     Jackson           MS     4,704 Capitol Building 111 
                                        E. Capitol Street 
                                        Suite 510 
                                        Jackson, MS 39201       482  JCSNMS1W       8035       2879                  ESPIRE BST
         --------------------------------------------------------------------------------------------------------------------------
  17     Jacksonville      FL     5,000 530 West Adams St. 
                                        Jacksonville, FL 32202  452  JCVLFL1W       7613       1245        904/358   BST
         --------------------------------------------------------------------------------------------------------------------------
  18  x  Kansas City       MO     7,693 The Bryant Building 
                                        1102 Grand Ave #300 
                                        Kansas City, MO         524  KSCYMO1W       7027       4202       816/221   SWB ESPIRE
         --------------------------------------------------------------------------------------------------------------------------
  19     Las Vegas         NV     2,525 4275 E. Sahara Ave 
                                        Units 19 & 20                                                              SPRINT
                                        Las Vegas, NV 89104     721  LSVGNV1W       3668       7422       702/244  NEXTLINK ACS
         --------------------------------------------------------------------------------------------------------------------------
  20  x  Los Angeles       CA     5,000 624 South Grand 
                                        Suite 1706 
                                        Los Angeles CA 90017    730  LSANCA1W       9213       7878       213/623  GST PBT MFS
         --------------------------------------------------------------------------------------------------------------------------
</TABLE>

<PAGE>
<TABLE>
<CAPTION>
  ================================================================================================================================
  Williams Network Onnet City List             X indicates InService
                                                                                            Horizontal
                                POP Sq.                                         Vertical    Coordin-    NPA/         Local Access
         City               St  Ft.         Address            LATA  CLLI CODE  Coordinate    ate       NXX          Vendor
  =================================================================================================================================
<S>                       <C>    <C>                            <C>  <C>        <C>         <C>         <C>        <C>
  21     Melbourne         FL     5,000 NE Corner of Line and 
                                        Lotana St Melbourne Fl  458  MLBRFL1W       7964.23    351.64              BST
         --------------------------------------------------------------------------------------------------------------------------
  22     Miami             FL    10,000 2115 NW 22nd Street 
                                        Miami, Fl 33142         460  MIAMFL1W       8350       534        305/325  BST MFS
         --------------------------------------------------------------------------------------------------------------------------
  23     Minneapolis       MN    10,000 511 11th Ave South 
                                        Minneapolis, MN 55415   528  MPLSMN1W       5780       4526       612/339  USWEST
         --------------------------------------------------------------------------------------------------------------------------
  24  x  New Orleans       LA     5,000 Poydrous Plaza 
                                        539 Loyola Ave Ste 2020 
                                        New Orleans, LA 70113   490  NWORLA1W       8483       2638       504/529  BST
         --------------------------------------------------------------------------------------------------------------------------
  25  x  New York          NY     5,323 60 Hudson Street 
                                        12th Floor                                                                 MFS
                                        New York, NY 10013      132  NYCMNY1W       5004       1406       212/571  BELLATLANTIC TW
         --------------------------------------------------------------------------------------------------------------------------
  26     Newark            NJ    20,000 165 Halsey Street                                                          MFS
                                        Newark, NJ 07102        224  NWRKNJ1W       5015       1430       973/643  BELLATLANTIC
         --------------------------------------------------------------------------------------------------------------------------
  27     Oklahoma City     OK    7,445 201 Robert S. Kerr 
                                        Suite 220 
                                        Oklahoma City, OK 73102 536  OKCYOK1W       7946       4372       405/232  SWB MFS COX
         --------------------------------------------------------------------------------------------------------------------------
  28     Orlando           FL   10,000 SW Corner of Division 
                                        & Columbia              458  ORLDFL1W       7957.64    1031.53             BST MFS
         --------------------------------------------------------------------------------------------------------------------------
  29  x  Philadelphia      PA    3,800 2401 Locust Street 
                                       4th Floor 
                                       Philadelphia, PA 19103   228  PHLAPA1W       5252       1461       215/568 BELL ATLANTIC MFS
         --------------------------------------------------------------------------------------------------------------------------
  30     Phoenix           AZ    2,500 info not yet available   666  PHNXAZ1W       9119       6742       502/204 USWEST MFS
         --------------------------------------------------------------------------------------------------------------------------
  31     Portland          OR    2,500  707 SW Washington St. 
                                        4th Floor 
                                        Portland, OR 97205      572  PTLDOR1W       6799       3915       503/417 ELI MFS SW
         --------------------------------------------------------------------------------------------------------------------------
  32  x  Raleigh           NC    5,000  3440 Tarheel Drive 
                                        Bldg. 3 Ste #105 
                                        Raleigh, NC 27609       425  RLGHNC1W       5330       1435       919/873 BST TW
         --------------------------------------------------------------------------------------------------------------------------
  33  x  Richmond          VA    1,500  3600 W Broad St 
                                        Ste 472 Richmond, VA    248  RCMDVA1W       5907       1479       304/359 BELLATLANTIC MEDIA
         --------------------------------------------------------------------------------------------------------------------------
  34     Rochester         NY    5,000  1 West Main Stuie 610 
                                        Rochester, NY 14608     974  ROCHNY1W       4912.92    2194.33            RCCHTEL MFS TW
         --------------------------------------------------------------------------------------------------------------------------
  35     Sacramento        CA    2,403  770 L Street Ste 120 
                                        Sacramento, CA 95814    725  SCRMCA1W       8303       3581       916/441 PBT MFS
         --------------------------------------------------------------------------------------------------------------------------
  36  x  Spartanburg       SC    4,212  BCT 145 N Church St 
                                        Spartanburg, SC 29306   430  SPBGSC1W       6809       1832       364/948    BST
         --------------------------------------------------------------------------------------------------------------------------
  37  x  St. Louis         MO    2,331  The Valley Building 
                                        900 Walnut St Ste 124 
                                        St. Louis, MO 63102     520 STLSMO01DSC     6807       2483       314/436    MFS SWB
         --------------------------------------------------------------------------------------------------------------------------
  38     Syracuse          NY    4,700  The Atrium Building 
                                        2 Clinton Square 
                                        Syracuse, NY 13202      136 SYRCNY1W        4797.54    1990.96    315/422   BELLATLANTIC
         --------------------------------------------------------------------------------------------------------------------------
  39     Tucson            AZ    5,000  135 & 139 North 5th Ave 
                                        Tuscon, AZ 85701        568 TCSNAZ1W        9346       5487       520/620    MFS USWEST
         --------------------------------------------------------------------------------------------------------------------------
  40  x  Tulsa             OK    5,238  100 W 5th Street 
                                        5th Floor 
                                        Tulsa, OK 74103         538 TULSOK1W        7708       4176       918/584    MFS ACSI SWB
         --------------------------------------------------------------------------------------------------------------------------
</TABLE>


<PAGE>

<TABLE>
<CAPTION>
  =================================================================================================================================
  Williams Network Onnet City List             X indicates InService
                                                                                            Horizontal
                                POP Sq.                                         Vertical    Coordin-    NPA/         Local Access
         City               St  Ft.         Address            LATA  CLLI CODE  Coordinate    ate       NXX          Vendor
  =================================================================================================================================
<S>                       <C>    <C>                            <C>  <C>        <C>         <C>         <C>        <C>
  41  x  Washington        DC    5,279  1220 L Street NW 
                                        Suite 200 
                                        Washington, DC 20910    236 WASHDC1W        5622       1582       202/408  BELLATLANTIC MFS
         --------------------------------------------------------------------------------------------------------------------------
  42     West Palm Beach   FL    5,000  SW Corner of Rosemary & 
                                        Second Street 

                                        West Palm Beach, FL     460 WP8HFL1W        3161.4     509.48     561/      BST
         --------------------------------------------------------------------------------------------------------------------------
</TABLE>



  Service provided between any of the cities listed above is considered On-Net.
Williams will update this listing periodically.





                                                 Confidential - WinStar/Williams






                         WIRELESS FIBERsm IRU AGREEMENT


                                 BY AND BETWEEN


                             WINSTAR WIRELESS, INC.


                                       AND


                          WILLIAMS COMMUNICATIONS, INC.






                        Effective as of December 17, 1998




<PAGE>

                                TABLE OF CONTENTS
<TABLE>
<S>                                                                                                              <C>

1.   DEFINITIONS..................................................................................................1
1.1.   Particular Terms...........................................................................................1
1.2.   Other Terms................................................................................................4

2.   SCOPE AND STRUCTURE..........................................................................................4
2.1.   General....................................................................................................4
2.2.   Term.......................................................................................................5
2.3.   Strategic Relationship.....................................................................................5

3.   GRANTS, RIGHTS AND RESPONSIBILITIES..........................................................................6
3.1.   WinStar Grant, Rights and Responsibilities.................................................................6
3.2.   WinStar Acceptance and Testing.............................................................................7
3.3.   Control of Facilities......................................................................................7
3.4.   Provisioning of Williams T-1s..............................................................................8
3.5.   Service Orders for Williams T-1s...........................................................................9
3.6.   Changes in Service Parameters.............................................................................10
3.7.   Delivery of Minimum Williams T-1 Inventory................................................................10

4.   OTHER PERFORMANCE AND SERVICES..............................................................................11
4.1.   Interconnection...........................................................................................11
4.2.   Collocation...............................................................................................11
4.3.   Maintenance...............................................................................................11
4.4.   Routine Maintenance.......................................................................................11
4.5.   Non-Routine Maintenance...................................................................................12
4.6.   Subcontractors............................................................................................12
4.7.   Williams Equipment........................................................................................12
4.8.   Performance Standards.....................................................................................12
4.9.   Disengagement Assistance..................................................................................12
4.10.  Relocation................................................................................................12
4.11.  Ancillary Services........................................................................................13

5.   CONTRACT ADMINISTRATION.....................................................................................13
5.1.   Reports and Meetings......................................................................................13
5.2.   Confidentiality...........................................................................................14

6.   CHARGES.....................................................................................................16
6.1.   General...................................................................................................16
6.2.   Taxes.....................................................................................................16
6.3.   Pass-Through Expenses.....................................................................................17
6.4.   Most Favored Customer Status..............................................................................17
6.5.   Benchmarking..............................................................................................18

7.   INVOICING AND PAYMENT.......................................................................................18
7.1.   Invoicing.................................................................................................18
7.2.   Payment Due...............................................................................................18
7.3.   Disputed Charges..........................................................................................19
7.4.   Late Interest.............................................................................................19

8.   COVENANTS, REPRESENTATIONS AND WARRANTIES...................................................................19
8.1.   Non-Infringement..........................................................................................19
8.2.   Authorization.............................................................................................19
8.3.   Wireless Fiber Connectivity...............................................................................20
8.4.   Disclaimer................................................................................................20

9.   INDEMNIFICATION.............................................................................................20
9.1.   Indemnities by Williams...................................................................................20
9.2.   Indemnities by WinStar....................................................................................21
9.3.   Indemnification Procedures................................................................................22
</TABLE>

                                      - i -
<PAGE>

<TABLE>
<S>                                                                                                             <C>
10.  LIABILITY, RISK OF LOSS AND INSURANCE.......................................................................22
10.1.  General Intent............................................................................................22
10.2.  Liability Restrictions....................................................................................23
10.3.  Insurance Requirements....................................................................................23
10.4.  Risk of Loss..............................................................................................24
10.5.  Force Majeure.............................................................................................24

11.  REMEDIES AND DISPUTE RESOLUTION.............................................................................25
11.1.  Cumulative Nature.........................................................................................25
11.2.  Informal Dispute Resolution...............................................................................25
11.3.  Arbitration...............................................................................................26
11.4.  Termination...............................................................................................27
11.5.  Suspension of Service.....................................................................................27
11.6.  Litigation................................................................................................27
11.7.  Continued Performance.....................................................................................28

12.  GENERAL.....................................................................................................28
12.1.  Binding Nature and Assignment.............................................................................28
12.2.  Entire Agreement..........................................................................................28
12.3.  Tariff....................................................................................................28
12.4.  Consents..................................................................................................29
12.5.  Restriction of Transmissions..............................................................................29
12.6.  Use and Ownership.........................................................................................29
12.7.  Non-Solicitation..........................................................................................29
12.8.  Notices...................................................................................................29
12.9.  Counterparts..............................................................................................30
12.10. Relationship of Parties...................................................................................30
12.11. Severability..............................................................................................30
12.12. Reasonableness, Consents and Approval.....................................................................30
12.13. Waiver of Default.........................................................................................30
12.14. Survival..................................................................................................31
12.15. Public Disclosures........................................................................................31
12.16. Third Party Beneficiaries.................................................................................31
12.17. Amendment.................................................................................................31
12.18. Order of Precedence.......................................................................................31
12.19. Interpretation............................................................................................32
12.20. Covenant of Good Faith....................................................................................32
</TABLE>



                        LIST OF SCHEDULES AND EXHIBITS
- --------------------------------------------------------------------------------
Schedule A        Scope and Services
                  Exhibit A-1: WinStar Target Markets
                  Exhibit A-2: Implementation Schedule
                  Exhibit A-3: Collocation
                  Exhibit A-4: Standards and Specifications
                  Exhibit A-5: Hub Implementation Forecast
                  Exhibit A-6: Williams Connectivity
Schedule B        Performance Standards
Schedule C        Charges


                                       ii


<PAGE>




                         WIRELESS FIBERsm IRU AGREEMENT

                                 BY AND BETWEEN

                             WINSTAR WIRELESS, INC.

                                       AND

                          WILLIAMS COMMUNICATIONS, INC.




         This WIRELESS FIBER IRU AGREEMENT (including the Exhibits and Schedules
attached  hereto,  the  "Agreement"),  effective  as of  December  17, 1998 (the
"Effective  Date"),  is entered into by and between  WINSTAR  WIRELESS,  INC., a
Delaware corporation with offices located at 230 Park Avenue, New York, New York
10169 ("WinStar"),  and WILLIAMS  COMMUNICATIONS,  INC., a Delaware  corporation
with offices located at One Williams Center, Tulsa, Oklahoma 74172 ("Williams").


         WHEREAS,  WinStar  is  a  fixed  wireless  services  telecommunications
provider  currently  planning to build-out in the  domestic  major  metropolitan
markets set forth in Exhibit A-1;


         WHEREAS,  Williams is a provider of high capacity long haul fiber optic
network transport and desires to utilize WinStar's  Wireless Fiber  Connectivity
(as hereinafter defined) in conjunction with its long haul network services; and


         WHEREAS,  upon the terms and subject to the conditions set forth below,
Williams  desires to acquire  from  WinStar,  and WinStar  desires to provide to
Williams, an exclusive,  indefeasible right to use certain of WinStar's Wireless
Fiber Connectivity on a private, non-common-carrier basis.


         NOW THEREFORE,  in consideration of the mutual promises set forth below
and  other  good and  valid  consideration,  the  receipt  of  which  is  hereby
acknowledged,  WinStar and Williams  (collectively,  the  "Parties"  and each, a
"Party") agree as follows:

1.   DEFINITIONS
     1.1. Particular Terms.

          As used in this Agreement:

          (a)  "Acceptance" has the meaning set forth in Exhibit A-4.

          (b)  "Acceptance  Date" means, for each Hub, the date of Acceptance as
               provided in Exhibit A-4.

          (c)  "Acceptance  Standards"  means the standards set forth in Exhibit
               A-4 with respect to the testing of the Hubs.

          (d)  "Affiliate"  means, with respect to any entity,  any other entity
               that directly,  or indirectly through one or more intermediaries,
               Controls,  or is Controlled  by, or is under common Control with,
               such entity.

                                       1
<PAGE>

          (e)  "Agreement"  has the  meaning  set forth in the  preamble to this
               Agreement.

          (f)  "Confidential  Information"  has the meaning set forth in Section
               5.2.

          (g)  "Control"  and  its  derivatives   means  legal,   beneficial  or
               equitable ownership,  directly or indirectly,  of more than fifty
               percent  (50%) of  outstanding  voting  capital  stock  (or other
               ownership  interest,  if  not  a  corporation)  of an  entity  or
               management or operational control over such entity.

          (h)  "Cost"  means  actual,  direct  costs  incurred  and  computed in
               accordance  with the  established  accounting  procedures used by
               WinStar to bill third  parties  for  reimbursable  projects.  All
               Costs shall be computed in  accordance  with  generally  accepted
               accounting principles. Such actual, direct costs include:

               (i)  Labor costs,  including  wages and  salaries,  and benefits,
                    plus the overhead  allocable  to such labor costs  (overhead
                    allocation  percentage  shall not  exceed the lesser of: (i)
                    the percentage  WinStar allocates to its internal  projects;
                    or (ii) thirty percent (30%)); and

               (ii) Other   direct  costs  and   Out-of-Pocket   Expenses  on  a
                    Pass-Through  Expenses basis (such as equipment,  materials,
                    supplies,  contract  services,  costs of  capital,  Required
                    Rights,  sales, use or similar taxes, etc.) plus ten percent
                    (10%) of such expenses, but

               (iii) Less any cost or expense reimbursed by a third party.

          (i)  "Domestic  Hub  Capacity"  means,  at the time in  question,  the
               aggregate  capacity of WinStar's  deployed Hubs within the United
               States.

          (j)  "Effective  Date" has the  meaning  set forth in the  preamble to
               this Agreement.

          (k)  "Governmental  Authorizations"  means all  licenses,  permits and
               authorizations  from  the  Federal   Communications   Commission,
               Federal   Aviation    Administration,    state   public   utility
               commissions, municipal authorities or any other governmental body
               that are  materially  necessary  or  required  for or used in the
               business  and  operations  of  WinStar  or the  provision  of the
               Wireless Fiber Connectivity.

          (l)  "Hub" has the meaning set forth in Schedule A.

          (m)  "Indefeasible   Right  of  Use"  or  "IRU"  means  an  exclusive,
               indefeasible   right  to  use  the   specified   Wireless   Fiber
               Connectivity as contemplated by this Agreement.

          (n)  "Intellectual   Property   Rights"   means   patent,   copyright,
               trademark,  trade secret or other proprietary rights with respect
               to any work product in which such rights could inure.

                                       2
<PAGE>

          (o)  "Lit Building" means a building that, at the time in question, is
               either  a Hub  provided  by  WinStar  or  equipped  with a  radio
               connection  to a Hub  provided by WinStar  utilizing  spectrum in
               which WinStar holds a license.

          (p)  "Losses"  means all  liabilities,  damages and related  costs and
               expenses (including fines, levies, assessments,  reasonable legal
               fees and disbursements  and costs of  investigation,  litigation,
               settlement,  judgment,  interest and penalties) directly incurred
               by a Party.

          (q)  "Maintenance"  means the network  operations,  administration and
               maintenance required for the continued performance of the WinStar
               Fiberless Connectivity.

          (r)  "Minimum  Williams  T-1  Inventory"  has the meaning set forth in
               Exhibit A-6.

          (s)  "Out-of-Pocket    Expenses"    means    reasonable   and   actual
               out-of-pocket  expenses  incurred by a Party,  but not  including
               that   Party's   overhead   costs   (or   allocations   thereof),
               administrative expenses or other mark-ups.

          (t)  "Party" and "Parties" have the meanings set forth in the preamble
               to this Agreement.

          (u)  "Pass-Through Expenses" means certain WinStar expenses, as agreed
               to between the Parties in writing,  which Williams  agrees to pay
               directly or reimburse on an Out-of-Pocket Expenses basis.

          (v)  "Prime Rate" means, in respect of any period,  the rate published
               as Chase  Manhattan's  prime rate in the Wall Street Journal,  or
               any successor  publication thereto, from time to time during such
               period.

          (w)  "Pro Rata Share" means a proportion  equal, for Williams,  to the
               Williams  Connectivity  and, for WinStar,  the  complement of the
               Williams Connectivity.

          (x)  "Qualified  Building"  means  a  building  that,  at the  time in
               question,  has a verified line of sight (per  WinStar's  standard
               practices)  to a Hub  provided  by  WinStar  and  for  which  the
               necessary  Required Rights have been obtained by, or provided to,
               WinStar.

          (y)  "Required Rights" means leases or licenses for access to, and use
               of, building roof areas and other antenna  staging  locations and
               interior  space  and  conduit  rights  as  necessary  to  provide
               Wireless Fiber Connectivity to a building.

          (z)  "Sector"   means   an   area   of   coverage   emanating   off  a
               point-to-multipoint radio on a Hub.

          (aa) "Sector  Capacity"  of any  given  Hub  means,  as of the date in
               question,  the transport  capacity of the relevant Sector of that
               Hub.

          (bb) "Start Date" means,  with respect to any Williams  T-1, the first
               day on which such service is provided.

          (cc) "T-1" means a circuit  (wire,  fiber or spectrum) with a capacity
               of 1.544 Mbps.

                                       3
<PAGE>

          (dd) "Term" has the meaning set forth in Section 2.2.

          (ee) "Williams"  has the  meaning  set forth in the  preamble  to this
               Agreement.

          (ff) "Williams Connectivity" has the meaning given in Exhibit A-6.

          (gg) "Williams IRU" has the meaning given in Section 3.1(a).

          (hh) "Williams T-1" has the meaning given in Section 3.1(a). Each such
               circuit shall traverse any two end-points on  the WinStar network
               (e.g., at  the  common  space  in a  Lit Building  or  at a local
               WinStar point  of  presence) and  shall be  deemed  provided when
               approved by Williams in accordance with Section 3.5(e).

          (ii) "WinStar"  has the  meaning  set  forth in the  preamble  to this
               Agreement.

          (jj) "WinStar Equipment" means the  telecommunications  equipment used
               by WinStar to implement the Wireless Fiber Connectivity.

          (kk) "WinStar  Target Market" means a city listed in Exhibit A-2 where
               WinStar  has at  least  one Hub to  provide  the  Wireless  Fiber
               Connectivity,  which list may be amended by WinStar  from time to
               time with notice to Williams (in accordance with Exhibit A-2).

          (ll) "Wireless  Fiber   Connectivity"   means  the  Wireless   Fibersm
               connectivity,  which  WinStar is authorized to provide at certain
               licensed radio frequency bandwidths.

     1.2. Other Terms.

          Other terms used in this Agreement are defined in the context in which
          they are used and have the meanings there indicated.

2.       SCOPE AND STRUCTURE

     2.1. General.

          (a)  This Agreement sets forth the general terms and conditions  under
               which WinStar grants Williams specific rights to certain capacity
               within the deployed Wireless Fiber Connectivity.


          (b)  The Parties  acknowledge  that this  Agreement  does not grant to
               WinStar an exclusive  privilege  to sell or otherwise  provide to
               Williams  any or all of the  transport  and  services of the type
               described in this  Agreement.  Williams  may contract  with other
               suppliers  for  the   procurement  of  comparable   transport  or
               services.  Subject to the Williams  IRU granted by WinStar  under
               this  Agreement,  WinStar is not restricted from selling to other
               entities any types of transport or services  including  the types
               of transport or services that are provided to Williams hereunder.

                                       4
<PAGE>

     2.2. Term.

          The term of this Agreement  (the "Term"),  with respect to each of the
          initial two hundred and  seventy  (270) Hubs  implemented  by WinStar,
          shall  begin on the  corresponding  Acceptance  Date and  continue  in
          effect for twenty-five (25) years from that time.

     2.3. Strategic Relationship.

          (a)  Resale of WinStar Product. Pursuant to terms to be agreed upon by
               the Parties after the Effective Date, WinStar will grant Williams
               the right to market and promote  certain  WinStar  voice and data
               products  (e.g.,  wireless  capacity,  professional  services and
               Internet connectivity) through its sales channel.

          (b)  Williams-Provided  Roof Rights and Building Access.  If requested
               by  WinStar,  Williams  shall  grant  to  WinStar,  at  no  cost,
               appropriate  roof,  riser,  conduit rights and interior space (in
               each  case,  in  quantities  to  be  mutually  agreed  upon  on a
               case-by-case  basis) rights to buildings in the United States for
               which  Williams  owns,  leases or occupies,  in whole or in part,
               that Williams can obtain (at reasonable cost) or has such rights.
               In  addition,  Williams  shall assist  WinStar in obtaining  such
               rights  with  respect to other  buildings  in the  United  States
               leased  or  occupied,  in whole or in part,  by  Williams  or its
               Affiliates,  including by actively  conveying to those Affiliates
               the  strategic  and  important  nature of the  relationship  with
               WinStar.  Williams  shall  provide  (and  periodically  update as
               reasonably  requested by WinStar)  WinStar with a written list of
               the addresses of all such real estate.

          (c)  Mutual   Marketing   Support.   WinStar  will  provide   Williams
               reasonable marketing support in connection with Williams' sale of
               the Williams T-1s and other WinStar voice and data products.

          (d)  Provisioning  and Billing OSS. The Parties will work  together in
               order to interface their  then-current  provisioning  and billing
               operational support system information (e.g.,  network events and
               statistics).   The  reasonable   costs   associated   with  these
               activities  shall be mutually  shared  between the  Parties.  If,
               after consultation with Williams,  WinStar is required to provide
               provisioning   and  billing   information   unique  to  Williams'
               wholesale  activities,  the  reasonable  costs of providing  such
               information shall be borne by Williams.

          (e)  Regulatory  Assistance.  If either  Party  affirmatively  takes a
               position in the domestic  regulatory  environment,  it will be in
               favor of a level playing field and in support of competition,  as
               such Party determines in its sole  discretion.  The Parties shall
               periodically (but at least  semi-annually)  meet to discuss their
               plans and objectives with respect to the regulatory environment.

3.  GRANTS, RIGHTS AND RESPONSIBILITIES

     3.1.     WinStar Grant, Rights and Responsibilities.

          (a)  Effective as of the  Acceptance  Date,  WinStar  hereby grants to
               Williams an exclusive  Indefeasible  Right of Use (the  "Williams
               IRU"),  for  the  purposes  described  herein,  in  the  Williams

 

<PAGE>

                                     5

               Connectivity  as  expressed  in  T-1  increments  over  time,  as
               provided in Exhibit  A-6 (the  "Williams  T-1s"),  subject to the
               additional  limitations  set forth in Subsection (c) below.  Such
               grant  does not convey  any legal  title to any real or  personal
               property,   including  the  spectrum,   physical   equipment  and
               connections used to effect the Domestic Hub Capacity.

          (b)  Subject  to the  terms of this  Agreement,  Williams  shall  have
               exclusive use of the Williams T-1s for any lawful  purpose during
               the Term.

          (c)  In addition to the Williams Connectivity  limitation set forth in
               Section  3.1(a),  the  Williams  T-1s  shall  be  subject  to the
               following limitations:

               (i)  Williams T-1s from any Lit Building that is connected to the
                    WinStar Hub through a point-to-point radio link may go up to
                    but shall not exceed fifteen percent (15%) of the bandwidth
                    capacity provided to that building notwithstanding WinStar's
                    usage of any or all of such capacity in that building.

               (ii) Williams   T-1s   that   are   to   be   implemented   using
                    point-to-multipoint  links between Lit Buildings in a Sector
                    and a WinStar Hub may go up to but shall not exceed  fifteen
                    percent  (15%) of the relevant  Sector  Capacity of that Hub
                    notwithstanding WinStar's usage of any or all of such Sector
                    Capacity in the Sector.

               (iii)For Qualified  Buildings lit at Williams'  expense  pursuant
                    to  Section   3.4(b)(ii),   the   limitation  set  forth  in
                    Subsection  (c)(i),  if  applicable,  shall be  increased to
                    fifty percent (50%) for  buildings  lit  point-to-point.  In
                    addition,  only  seventy-five percent (75%) of the Williams
                    T-1s in such  buildings  will  count  towards  the  Williams
                    Connectivity limitation set forth in Subsection (a) above.

               (iv) In  accordance  with  Section 3.6,  each  Williams T-1 shall
                    count  against the  limitations  set forth above for one (1)
                    year,  regardless  of  whether  or not the  duration  of its
                    connectivity  lasts less than one (1) year.  After its first
                    year of connectivity,  each Williams T-1 shall count against
                    such limitations until disconnected.

               (v)  Williams may order Williams  Connectivity  only in multiples
                    of T-1 line speeds.  Orders for line speeds  higher than T-1
                    will count proportionately  toward the limitations set forth
                    in this  Subsection  (c). For example,  a DS-3 will count as
                    twenty-eight  (28) T-1s. Apart from the applicability of the
                    limitations,  the line speeds of the  circuits  constituting
                    the  Williams  Connectivity  shall  have  no  effect  on the
                    respective rights and obligations of the Parties.

     3.2. WinStar Acceptance and Testing.

          (a)  As of the Effective Date,  Williams hereby agrees that Acceptance
               of  the  initial  fifty-seven  (57)  Hubs  (the  "Initial  Hubs")
               deployed  by  WinStar  is  deemed  to  have   occurred.   WinStar
               represents  and  warrants  that  the  Initial  Hubs  have met the
               Acceptance Standards as of the Effective Date.


                                       6
<PAGE>

          (b)  Prior to the use of each Hub  deployed by WinStar  following  the
               Effective Date, WinStar will have performed testing procedures in
               accordance  with  Exhibit  A-4,  which are  sufficient  to verify
               compliance with Acceptance Standards. Acceptance of each such Hub
               shall occur as set forth in Exhibit A-4.

     3.3. Control of Facilities.

          Notwithstanding any other provision of this Agreement, WinStar has and
          shall at all times  continue to retain  control over all FCC licenses,
          equipment and facilities  subject to this Agreement and shall have, at
          all times,  required  access to all of the  equipment  and  facilities
          installed  by it  pursuant  to  this  Agreement.  In  exercising  this
          control,  WinStar will not disturb or interfere with the Williams T-1s
          without  good  cause,  such as a  request  from  the FCC to shut  down
          interfering transmissions, emergency service restoration or correction
          of other technical  problems.  WinStar shall provide  Williams with as
          much  prior  notice  as is  reasonably  practicable  in  the  case  of
          emergency  disruptions  of the Wireless  Fiber  Connectivity.  WinStar
          shall, with the reasonable cooperation and assistance of Williams, (i)
          operate its business in all material  respects in accordance  with the
          terms  of  the  Governmental  Authorizations  and  (ii)  maintain  the
          validity of the Governmental Authorizations. WinStar agrees to provide
          Williams with notice in the event matters come to WinStar's  attention
          that could  materially  prevent it from meeting its obligations  under
          this Agreement.  In this regard, WinStar and Williams further agree as
          follows:

          (a)  Williams  shall not  represent  itself  as the  holder of any FCC
               licenses issued to WinStar.

          (b)  Any  communications  by either Party with the FCC  regarding  the
               subject matter of this Agreement  shall require the other's prior
               written approval.

          (c)  Neither WinStar nor Williams shall represent  itself as the legal
               representative   of  the  other  before  the  FCC  or  any  state
               regulatory body. Except as otherwise required by law, all filings
               made before  regulatory  bodies with respect to WinStar's license
               or the services  provided  hereunder  shall be made by and in the
               name of WinStar.  WinStar and Williams will  cooperate  with each
               other with respect to  regulatory  matters  concerning  WinStar's
               licenses and the services  provided  pursuant to this  Agreement;
               provided,  however,  this will not relieve WinStar from complying
               with the Governmental Authorizations.

          (d)  Nothing in this  Agreement  is  intended  to diminish or restrict
               WinStar's  obligations as an FCC licensee and both Parties desire
               that  this  Agreement  be in full  compliance  with the rules and
               regulations  of the FCC and any state or local  jurisdiction.  If
               the FCC or any state  regulatory  body of competent  jurisdiction
               determines  that any  provision  of this  Agreement  violates any
               applicable  rules,  policies or  regulations,  both Parties shall
               bear  their  respective  Pro Rata  Share of costs to  immediately
               bring this Agreement into compliance,  consistent with the intent
               of this Agreement.

          (e)  It is expressly  understood  by WinStar and Williams that nothing
               in this  Agreement is intended to give to Williams any right that
               would be deemed to constitute a transfer of control (as "control"
               is defined in the Communications Act of 1934, as amended,  or any
               applicable  FCC  rules or case  law) of one or more of  WinStar's
               licenses from WinStar to Williams.


                                       7
<PAGE>

     3.4. Provisioning of Williams T-1s.

          Except as otherwise provided in this Section 3.4, WinStar,  at its own
          expense, shall be solely responsible for obtaining and maintaining all
          rights and privileges  (including  Required  Rights,  space and power)
          that are  necessary  for WinStar to provide the  Williams  T-1s to the
          WinStar common space.

          (a)  Subject to the limitations set forth in Section 3.1, Williams may
               order  T-1s  to be  connected  to any  Qualified  Building  (or a
               building that would be a Qualified Building but for the obtaining
               of Required Rights). If Williams orders Williams T-1s that are to
               be connected to a Lit  Building,  WinStar  will  provision,  on a
               non-discriminatory  basis,  those T-1s to the common  space at no
               additional cost with an objective of completing that provisioning
               within thirty (30) days from the date of Williams' order.

          (b)  If Williams  orders  Williams  T-1s that are to be connected to a
               Qualified  Building  (or a  building  that  would be a  Qualified
               Building but for the obtaining of Required  Rights) that is not a
               Lit Building:

               (i)  WinStar shall  determine  within ninety (90) days of receipt
                    of notice from Williams whether, in its sole discretion,  it
                    will light such  building at its own expense.  If WinStar so
                    elects,  that notice shall set forth a target  delivery date
                    and WinStar  shall light that building and  provision,  on a
                    non-discriminatory  basis, the T-1s to the common space with
                    the  objective of completing  such  activities by the target
                    delivery date.

               (ii) If  WinStar  elects not to light  such  building  at its own
                    expense,  WinStar  will light the  building  upon  Williams'
                    request,   in  accordance   with  a  target   delivery  date
                    established by WinStar. Williams shall pay for such lighting
                    at  WinStar's  Cost of  performance.  Additionally,  in such
                    event,   Williams  shall  be  responsible,   with  WinStar's
                    assistance,  for  obtaining  and  maintaining,  at Williams'
                    expense,  all  necessary  rights and  privileges  (including
                    Required  Rights,  space and power).  Lighting,  pursuant to
                    this Subsection 3.4(b)(ii),  of more than five (5) buildings
                    connected to a single Hub,  whether singly or in combination
                    over any  period  of time,  shall be  subject  to  WinStar's
                    approval which shall not be unreasonably withheld.

          (c)  When WinStar  lights a building for  provisioning a Williams T-1,
               Williams will either:

               (i)  Perform  inside  wiring for its  customers in such  building
                    subject  both to  obtaining  any  necessary  consents and to
                    WinStar's   then-current    installation    guidelines   and
                    specifications; or

               (ii) Have WinStar perform such wiring at WinStar's Cost.

                                       8
<PAGE>

     3.5. Service Orders for Williams T-1s.

          (a)  The  implementation  of a Williams T-1 to a Lit Building shall be
               requested on WinStar's Service Order forms in effect from time to
               time ("Service Orders").  Each Service Order shall reference this
               Agreement.  WinStar  reserves  the  right not to accept a Service
               Order that does not conform with the terms and conditions of this
               Agreement  and such  non-conforming  Service  Order shall have no
               force or effect hereunder.

          (b)  Each  Service  Order will  indicate a  requested  Start Date (the
               "Requested  Start Date") for the  implementation  of the Williams
               T-1s to a Lit  Building,  the desired term of the Williams  T-1s,
               and any other  parameters  required.  WinStar  shall  acknowledge
               receipt of the Service Order, on average, within forty-eight (48)
               hours (an "Acknowledgement").

          (c)  Once a Service  Order is placed,  Williams  may cancel it only by
               notice  of  cancellation  not less  then ten (10)  days  prior to
               delivery of the  corresponding  Williams  T-1, and payment of any
               specified  cancellation  fee.  Williams  agrees  that the  actual
               damages in the event of such  cancellation  would be difficult or
               impossible  to  ascertain,   and  that  the  cancellation  charge
               including  those set forth  herein is  consequently  intended  to
               establish liquidated damages and not a penalty.

          (d)  Any  conflicting,  different or additional  terms and  conditions
               contained  in  Williams'   acknowledgment  or  Service  Order  or
               elsewhere  are  deemed  objected  to by  WinStar  and  shall  not
               constitute  part  of  this   Agreement.   No  action  by  WinStar
               (including  fulfillment of such Service Order) shall be construed
               as binding or estopping WinStar with respect to such conflicting,
               different or  additional  term or  condition,  unless the Service
               Order  containing  said term or  condition  has been signed by an
               authorized representative of WinStar.

          (e)  WinStar  shall make  reasonable  efforts to provide the  Williams
               T-1s  within the  service  implementation  interval  set forth in
               Section  3.5(b) or by Williams'  Requested  Start Date.  Williams
               T-1s shall begin on the date WinStar  issues  notice that service
               is  available   (the  "Start  of  Service   Notice"  or  "SOSN"),
               indicating  the  Williams  T-1 has  been  tested  by  WinStar  in
               accordance with WinStar's  standard  specifications  and that the
               service meets or exceeds those specifications.

          (f)  Williams  may  reasonably  request  one  or  more  delays  in the
               Requested Start Date of a Service Order, a move, or rearrangement
               if WinStar  receives the delay request at least fifteen (15) days
               prior to the Requested  Start Date and the  requested  delay does
               not extend the  Requested  Start Date more than thirty  (30) days
               from the original date thereof.  If Williams delays the Requested
               Start Date (or as gauged by the SOSN,  if issued for a date after
               the  Requested  Start Date) by more than  thirty  (30) days,  the
               Williams  T-1s  will  count  against  the  Minimum  Williams  T-1
               Inventory and the Williams  Connectivity  for a period of one (1)
               year.  This count against the Minimum  Williams T-1 Inventory and
               Williams  Connectivity  will be effective  thirty (30) days after
               the Requested Start Date.


                                       9
<PAGE>

     3.6. Changes in Service Parameters.

          Following the relevant  Start Date for any Williams T-1,  Williams may
          disconnect  or  reconfigure  that  service upon sixty (60) days' prior
          written notice.  If that action relates to a Williams T-1 that has not
          been in place for at least one (1) year from its Start Date,  (i) such
          Williams T-1 will continue to count  against the Minimum  Williams T-1
          Inventory and Williams  Connectivity  for the remainder of the one (1)
          year period;  and (ii) Williams  shall also pay WinStar the additional
          charges   incurred   by  WinStar   that  are   associated   with  that
          disconnection  or  reconfiguration.  Subsection  (ii) shall also apply
          with respect to a cancellation as provided in Section 3.5(c).

     3.7. Delivery of Minimum Williams T-1 Inventory.

          (a)  Availability  Date.  The  "Availability  Date" shall mean (i) the
               Effective Date with respect to the Minimum Williams T-1 Inventory
               identified  in Exhibit  A-6 to be  provided to Williams as of the
               Effective  Date,  and (ii)  December  31st of each  calendar year
               following  1998  through the end of the Term with respect to each
               annual  number of Minimum  Williams T-1  Inventory  identified in
               Exhibit A-6 for such calendar year. The "Deadline  Date" shall be
               sixty (60) days after the later of (i) such planned  Availability
               Date or (ii) the planned  Availability  Date as  extended  due to
               unforeseen events not in the reasonable control of WinStar (other
               than as due to WinStar's negligence),  Force Majeure events or as
               expressly  permitted  by  this  Agreement.   WinStar  shall  make
               available each of its annual Minimum  Williams T-1 Inventories by
               the applicable Deadline Date. WinStar shall give Williams as much
               prior notice as reasonably  possible if, to the best of WinStar's
               knowledge,  there  is a  foreseeable  risk  that  it  may  miss a
               Deadline Date for its Minimum Williams T-1 Inventory.

          (b)  Failure to Meet Deadline Date. If WinStar fails to make available
               the Minimum  Williams T-1  Inventory by its  applicable  Deadline
               Date, and the Parties are unable,  in good faith,  to agree to an
               alternative  Deadline Date, Williams' sole and exclusive monetary
               remedy for such failure shall be to obtain Cover (as  hereinafter
               defined)  beginning on the  Deadline  Date for the number of T-1s
               not made available.  "Cover" shall be satisfied by obtaining,  at
               WinStar's  expense,  the  number  of T-1s  that  would  have been
               available  had  WinStar  made  available  the  entire  applicable
               Minimum  Williams T-1  Inventory.  Once  WinStar  makes such T-1s
               available,  the Parties will work together to migrate the T-1s to
               WinStar at WinStar's sole cost and expense.

4.       OTHER PERFORMANCE AND SERVICES

     4.1.     Interconnection.

          (a)  With respect to each of the WinStar Target  Markets,  the Parties
               shall mutually  determine the most efficient  manner of providing
               the required connectivity ("Interconnection") between the WinStar
               and Williams points of presence,  whether  through  then-existing
               installed capacity, implementation of new capacity or third party
               arrangements. In addition, the Parties shall set and periodically
               review the schedule  (timing and priority) of  implementation  of
               those  Interconnection   facilities  and  shall  adhere  to  that
               schedule in implementing such facilities.


                                       10
<PAGE>

          (b)  The  Parties  shall  allocate  the costs of each  Interconnection
               facility as follows:

               (i)  The  Parties  shall  mutually  agree upon a forecast of each
                    Party's usage of that  Interconnection  facility  during the
                    first  year  after  implementation  (the  "Forecast").   The
                    non-recurring  costs associated with the  implementation  of
                    that  facility and the  recurring  cost thereof in the first
                    month of operation (in aggregate, the "Start-up Costs") will
                    be  allocated  pro rata  between the Parties  based upon the
                    Forecast. One year thereafter the Parties shall re-calculate
                    the allocation of the Start-up Costs by substituting  actual
                    usage during the  preceding  year in place of the  Forecast.
                    Based upon that recalculation, Williams shall pay or receive
                    a refund, in either case equal to the difference between the
                    initial   allocation   of  the   Start-up   Costs   and  the
                    recalculated amount, plus interest at the Prime Rate for the
                    applicable period.

               (ii) On  a  quarterly  basis,  the  Parties  shall  allocate  the
                    periodic  recurring costs of that  Interconnection  facility
                    pro rata between the Parties  based upon actual usage during
                    the preceding quarter.

               (iii)Following  the  Effective  Date,  the Parties will  mutually
                    develop appropriate procedures to implement the foregoing.

     4.2. Collocation.

          Exhibit A-3 sets forth the collocation services, terms and conditions.

     4.3. Maintenance.

          WinStar shall be  responsible  for providing  maintenance,  repair and
          testing on all WinStar Equipment used to provide the Williams T-1s, in
          accordance with its then-current  standard policies and procedures,  a
          portion  of which is  attached  hereto as  Exhibit  A-4.  Williams  is
          prohibited  from  providing  any  maintenance,  repair or testing with
          regard to WinStar Equipment.

     4.4. Routine Maintenance.

          During  the  Term,   WinStar  shall   perform  all  required   Routine
          Maintenance  Services at the charges set forth in Schedule C. "Routine
          Maintenance  Services"  means  the  work  specifically  identified  as
          Routine Maintenance Services in Article 5 of Schedule A, provided that
          Routine  Maintenance  Services  excludes  work for which  Williams  is
          obligated  to  reimburse  WinStar  for all or a  portion  of the Costs
          incurred pursuant to other provisions of this Agreement.

     4.5. Non-Routine Maintenance.

          Williams  shall pay its Pro Rata Share of  WinStar's  direct Costs for
          maintenance in respect of the Williams Connectivity other than Routine
          Maintenance  Services, if the Cost of such work relating to any single
          event or multiple related events is greater than Five Thousand Dollars
          ($5,000.00).

                                       11
<PAGE>

     4.6. Subcontractors.

          WinStar may subcontract provisioning,  testing,  maintenance,  repair,
          restoration, relocation or other operational and technical services it
          is obligated to provide hereunder or may have the underlying  facility
          owner or its contractor perform such obligations.  Such subcontracting
          shall not relieve WinStar of any obligations under this Agreement.
     
     4.7. Williams Equipment.

          WinStar's  maintenance  and repair  obligations  under this  Agreement
          shall not include  maintenance,  repair or  replacement  of  Williams'
          equipment.

     4.8. Performance Standards.

          Except as  otherwise  set forth in Schedule B, for the purpose of this
          Agreement   the   normal   standards   of   performance   within   the
          telecommunications  industry  in  the  relevant  market  shall  be the
          measure of whether a Party's performance is reasonable and timely.

     4.9. Disengagement Assistance.

          Upon  termination  or  expiration  of this  Agreement,  WinStar  shall
          provide   Williams  and  its  designated  third  party  providers  all
          reasonable  assistance as necessary to effect a smooth transition to a
          new supplier.

     4.10. Relocation.

          (a)  If WinStar  determines for bona fide operational  reasons,  or is
               required by a third party  acting  pursuant  to  condemnation  or
               similar authority or by a governmental entity, to relocate all or
               any portion of a Hub or any of the facilities used or required in
               providing  Williams with the Williams IRU,  WinStar shall, to the
               extent  practicable,  provide  Williams  sixty (60)  days'  prior
               notice and shall proceed with such relocation. WinStar shall have
               the  right to  direct  such  relocation,  including  the right to
               determine  the extent  of, the timing of, and  methods to be used
               for such relocation, provided that any such relocation:

               (i)  Shall be  constructed  and  tested  in  accordance  with the
                    specifications  and requirements set forth in this Agreement
                    and applicable Exhibits;

               (ii) Shall  not  result  in a  materially  adverse  change to the
                    operations or performance of the Hub, and

               (iii) Shall not unreasonably interrupt service on the Hub.

               For purposes of this Section 4.10, a WinStar  relocation shall be
               for bona fide  operational  reasons if it is  undertaken  in good
               faith  (i) to settle  or avoid a bona  fide  threatened  or filed
               condemnation  action  or order  by a  governmental  authority  to
               relocate, (ii) to reduce the likelihood of physical damage, (iii)
               as the  result  of a  Force  Majeure  Event,  or (iv)  for  other
               operational  reasons to which  Williams has  consented,  provided
               that  Williams  shall not  unreasonably  withhold  such  consent.
               WinStar shall use  reasonable  efforts to contest any exercise of
               condemnation  authority that would require a relocation  pursuant
               to this Section 4.10.

                                       12
<PAGE>

          (b)  Unless such  relocation is  necessitated by a breach of WinStar's
               obligations  under  this  Agreement,   Williams  shall  reimburse
               WinStar for the Costs incurred in the same manner and to the same
               extent as set forth for  reimbursement  for Costs of  maintenance
               other than for Routine Maintenance Services in Section 4.5.

     4.11. Ancillary Services.

          WinStar  may also  provide  other  services  to  Williams  for reasons
          including: (a) Williams' request to expedite Williams T-1 availability
          to a date earlier than WinStar's published  installation interval or a
          previously  accepted  Start Date;  (b)  Williams T-1 redesign or other
          activity   occasioned  by  receipt  of  inaccurate   information  from
          Williams; (c) Williams' request for use of facilities other than those
          selected by WinStar for provision of the Wireless  Fiber  Connectivity
          ("facilities" for this purpose shall not include buildings that became
          Lit  Buildings   pursuant  to  Section   3.4(b)(i));   and  (d)  other
          circumstances in which  extraordinary costs and expenses are generated
          at  the  written   request  of  Williams   and   incurred  by  WinStar
          (collectively, "Ancillary Services").

5.  CONTRACT ADMINISTRATION

     5.1. Reports and Meetings.

          (a)  Within thirty (30) days of the Effective  Date, the Parties shall
               mutually  agree  upon a set of  monthly  reports  to be issued by
               WinStar to Williams. WinStar will provide Williams with suggested
               formats for such reports for Williams'  review and  approval.  As
               one such  report,  WinStar  will  provide a  monthly  performance
               report  that   describes   WinStar's   deployment  of  the  Hubs,
               availability of the applicable Minimum Williams T-1 Inventory and
               a forecast  of upcoming  WinStar  Target  Market  implementations
               (including Hubs, buildings and addresses).

          (b)  Within thirty (30) days of the Effective  Date, the Parties shall
               mutually agree upon a set of regular management meetings. WinStar
               will prepare and circulate an agenda  sufficiently  in advance of
               each such meeting to give  participants an opportunity to prepare
               for the meeting and will  incorporate  into such agenda any items
               that Williams desires to discuss.  At Williams' request,  WinStar
               will prepare and circulate minutes promptly after a meeting.

     5.2. Confidentiality.

          (a)  Confidential  Information.  Williams and WinStar each acknowledge
               that they may be furnished with, receive or otherwise have access
               to  information  of or concerning the other Party that such Party
               considers  to be  confidential,  proprietary,  a trade  secret or
               otherwise  restricted.  As used in this  Agreement and subject to
               Section (c), "Confidential Information" means all information, in
               any form,  furnished or made available  directly or indirectly by
               one Party (the  "Disclosing  Party") to the other (the "Receiving
               Party")  that (i)  concerns the  operations,  facilities,  plans,
               affairs and  businesses of the  Disclosing  Party,  the financial
               affairs  of  the  Disclosing  Party,  and  the  relations  of the
               Disclosing  Party  with  its  customers,  employees  and  service
               providers,   or  (ii)   is   marked   confidential,   restricted,


                                       13

<PAGE>


               proprietary,  or  with  a  similar  designation.  The  terms  and
               conditions  of  this  Agreement  shall  be  deemed   Confidential
               Information, but may be disclosed pursuant to this Section 5.2 or
               Section 12.15.

          (b)  Obligations.

               (i)  Each  Party's  Confidential  Information  shall  remain  the
                    property  of  that  Party  except  as   expressly   provided
                    otherwise by the other  provisions of this  Agreement.  Each
                    Party shall each use at least the same  degree of care,  but
                    in any event no less than a  reasonable  degree of care,  to
                    prevent unauthorized disclosure of Confidential  Information
                    as it employs to avoid  unauthorized  disclosure  of its own
                    information  of  a  similar  nature.   Except  as  otherwise
                    permitted   hereunder,   the  Parties  may   disclose   such
                    information  (A) to their  respective  directors,  officers,
                    managers,  employees,  agents,  contractors  and consultants
                    (collectively,    "Representatives"),    (B)   to   entities
                    performing  services required  hereunder only where: (1) use
                    of such entity is authorized under this Agreement,  (2) such
                    disclosure  is necessary or  otherwise  naturally  occurs in
                    that entity's scope of responsibility, (3) the entity agrees
                    in  writing  to assume  the  obligations  described  in this
                    Subsection (b). Any disclosure to such entity shall be under
                    substantially the same confidentiality  terms and conditions
                    set forth herein.

               (ii) Each Party  shall take  reasonable  steps to ensure that its
                    (and  its  Affiliates')  Representatives  comply  with  this
                    Subsection  (b). In the event of any  disclosure or loss of,
                    or inability to account for, any Confidential Information of
                    the Disclosing Party, the Receiving Party shall promptly, at
                    its own expense: (A) notify the Disclosing Party in writing;
                    and (B) take such actions as may be necessary  and cooperate
                    in all  reasonable  respects  with the  Disclosing  Party to
                    minimize the violation and any damage resulting therefrom.

               (iii)Either Party may disclose the terms and  conditions  of this
                    Agreement  to any third party that (A) has  expressed a bona
                    fide  interest  in  consummating  a  significant  financing,
                    merger or acquisition or other corporate transaction between
                    such  third  party  and  such  Party,  (B) has a  reasonable
                    ability   (financial  and  otherwise)  to  consummate   such
                    transaction,  and (C) has executed a nondisclosure agreement
                    that includes  within its scope the terms and  conditions of
                    this  Agreement  and also  includes a procedure to limit the
                    extent of copying and distribution thereof. Each Party shall
                    endeavor to delay the disclosure of the terms and conditions
                    of this Agreement until the status of discussions concerning
                    such  transaction  warrants  such  disclosure.  In addition,
                    either party (or either party's Affiliates) may disclose the
                    terms and  conditions of this  Agreement as such party deems
                    appropriate   to  prepare   for  IPOs  or  major   corporate
                    transactions.   Any  disclosure  to  such  entity  shall  be
                    substantially  under  the  same  confidentiality  terms  and
                    conditions as provided herein.

                                       14
<PAGE>

          (c)  Exclusions.   "Confidential   Information"   shall   exclude  any
               particular information that the Receiving Party can demonstrate:

               (i)  At the time of  disclosure,  was in the public  domain or in
                    the rightful possession of the Receiving Party;

               (ii) After disclosure,  is published or otherwise becomes part of
                    the public domain through no fault of the Receiving Party;

               (iii)Was received after  disclosure  from a third party who had a
                    lawful right to disclose such  information  to the Receiving
                    Party without any  obligation to restrict its further use or
                    disclosure;

               (iv) Was  independently  developed by the Receiving Party without
                    reference  to  Confidential  Information  of the  Disclosing
                    Party; or

               (v)  Was required to be disclosed to satisfy a legal  requirement
                    of a competent  government body; provided that,  immediately
                    upon  receiving  such  request and to the extent that it may
                    legally do so, the Receiving  Party  advises the  Disclosing
                    Party promptly and prior to making such  disclosure in order
                    that the Disclosing Party may interpose an objection to such
                    disclosure,  take action to assure confidential  handling of
                    the Confidential  Information,  or take such other action as
                    it   deems   appropriate   to   protect   the   Confidential
                    Information.

          (d)  No Implied  Rights.  Nothing  contained in this Section  shall be
               construed  as  obligating  a Party to disclose  its  Confidential
               Information  to the other Party,  or as granting to or conferring
               on a Party, expressly or impliedly,  any rights or license to the
               Confidential Information of the other Party.

6.   CHARGES

     6.1. General.

          The charging  mechanisms and pricing  methodologies for Wireless Fiber
          Connectivity and maintenance and collocation services are set forth in
          Schedule C. 

     6.2. Taxes.

          The Parties' respective responsibilities for taxes arising under or in
          connection with this Agreement shall be as follows:

          (a)  Each Party shall be  responsible  for personal  property taxes on
               property it owns or leases,  for franchise and privilege taxes on
               its  business,  and for  taxes  based on its net  income or gross
               receipts;  provided,  however, that Williams shall be responsible
               for its proportionate share (based upon the proportion of the Hub
               or building capacity used for Williams T-1) of any property taxes
               (or similar levies) assessed as a result of the implementation of
               any Williams T-1.


                                       15
<PAGE>

          (b)  Williams  shall  timely  report and pay any and all  sales,  use,
               income,  gross receipts,  excise,  transfer,  ad valorem or other
               taxes,  and any and all  franchise  fees or similar fees assessed
               against  it due to the  Williams  IRU or its use of the  Williams
               T-1s.

          (c)  If a sales, use, excise, value-added,  services,  consumption, or
               other tax is  assessed on the  provision  of the  Wireless  Fiber
               Connectivity,  Maintenance  or any other  services,  the  Parties
               shall  work  together  to  segregate  the  payments   under  this
               Agreement into three (3) payment streams:

               (i)  Payments for taxable items;

               (ii) Payments where Williams  functions merely as a payment agent
                    for WinStar; and

               (iii) Payments for other nontaxable items.

          (d)  The Parties agree to cooperate  with each other to enable each to
               determine  more  accurately its own tax liability and to minimize
               such  liability to the extent legally  permissible.  Each invoice
               shall separately  state the amounts of any taxes collected.  Each
               Party shall  provide and make  available  to the other any resale
               certificates  and other  exemption  certificates  or  information
               reasonably  requested by either Party that is  applicable  to the
               subject matter of this Agreement.

          (e)  Each Party shall promptly notify the other of, and coordinate the
               response to and  settlement  of, any claim for taxes  asserted by
               applicable  taxing  authorities  for  which  the  other  Party is
               responsible hereunder. With respect to any claim arising out of a
               form or return  signed by a Party to this  Agreement,  such Party
               shall  have the right to elect to  control  the  response  to and
               settlement  of the  claim,  but the other  Party  shall  have all
               rights to participate in the responses and  settlements  that are
               appropriate to its potential responsibilities or liabilities.

     6.3. Pass-Through Expenses.

          For each  Pass-Through  Expense,  if any,  WinStar  shall  review  the
          invoiced  charges and  determine  whether  such charges are proper and
          valid.  Unless the  Parties  mutually  agree  otherwise,  Pass-Through
          Expenses will be paid directly by Williams.

     6.4. Most Favored Customer Status.

          (a)  Williams T-1s. With regard to the Williams Connectivity, Williams
               shall have most favored customer protection as follows:

          (i)  During the twenty-four (24) months following the Effective Date,
               if WinStar enters into an agreement with another party to provide
               Wireless Fiber Connectivity and the overall pricing ("Financial
               Terms") of such services is not Comparable (as hereinafter
               defined) to that provided to Williams pursuant to this Agreement
               with regard to the Williams Connectivity, WinStar shall promptly
               notify Williams in writing of such more favorable Financial
               Terms. WinStar shall be under no obligation to disclose to
               Williams the identify of any such third party or any other
               provisions of such a contract that are not more favorable than
               those provided to Williams. As used in this Section, "Comparable"


                    

                                       16
<PAGE>


               means not less than one-half the price, after adjustments to take
               into account all differences attributable to volume, terms and
               conditions, advances in technology, passage of time, market
               conditions or strategic relationship value.

          (ii) If WinStar sells Wireless Fiber Connectivity to a third party on
               Financial Terms that are not Comparable to those provided
               hereunder, Williams shall be entitled to an adjustment of the
               amounts paid with regard to the Williams Connectivity. Such
               adjustment shall be equal to twice the aggregate amount necessary
               to make the Financial Terms Comparable and shall be credited in
               such amounts as correspond to the timing of Williams' payment
               obligations hereunder. Upon payment or credit of such adjustment
               to Williams, the Financial Terms of this Agreement shall be
               deemed to be those more favorable Financial Terms for the purpose
               of future applications of this Section. Nothing in this Section
               6.4 shall be deemed to require WinStar to sell more Wireless
               Fiber Connectivity than the Williams Connectivity.

          (b)  Excess  Connectivity.  With regard to Wireless Fiber Connectivity
               in excess of the Williams  Connectivity  or Williams T-1 Ceiling,
               as appropriate ("Excess Connectivity"),  Williams shall have most
               favored customer protection as follows:

          (i)  During the Term, if WinStar enters into an agreement with another
               part to provide Wireless Fiber Connectivity and the Financial
               Terms of such services are not Comparable (as hereinafter
               defined) to that provided to Williams for Excess Connectivity
               pursuant to this Agreement, WinStar shall promptly notify
               Williams in writing of such more favorable Financial Terms.
               WinStar shall be under no obligation to disclose to Williams the
               identity of any such third party or any other provisions of such
               a contract that are not more favorable than those provided to
               Williams. As used in this Section, "Comparable" means an
               equivalent price, after adjustments to take into account all
               differences attributable to volume, terms and conditions,
               advances in technology, passage of time, market conditions or
               strategic relationship value.

          (ii) If WinStar sells Wireless Fiber Connectivity to a third party on
               Financial Terms that are not Comparable to those provided
               hereunder with regard to Excess Connectivity, Williams shall be
               entitled to an adjustment. Such adjustment shall be equal to the
               amount necessary to make the Financial Terms Comparable and shall
               be credited in such amounts as correspond to the timing of
               Williams' payment obligations hereunder. Upon payment or credit
               of such adjustment to Williams, the Financial Terms of this
               Agreement shall be deemed to be those more favorable Financial
               Terms for the purpose of future applications of this Section.

                                       17
<PAGE>

     6.5. Benchmarking.

          (a)  Wireless Fiber  Connectivity  offered by WinStar in excess of the
               Williams  Connectivity,  if any, shall be of equivalent or better
               quality,   availability   and  price  when  compared  to  similar
               offerings in the  marketplace.  However,  nothing in this Section
               6.5 shall be  deemed to  require  WinStar  to sell more  Wireless
               Fiber Connectivity than the Williams Connectivity.

          (b)  Within  180 days  after the  Effective  Date,  the  Parties  will
               jointly  establish  a  benchmarking  measurement  and  comparison
               process  (the  "Benchmarking  Process")  designed to  objectively
               evaluate  whether the Wireless  Fiber  Connectivity  purchased by
               Williams in excess of the Williams  Connectivity is of equivalent
               or better quality,  availability and price as compared to similar
               services  generally  available in the market for similar size and
               scope  requirements  ("Market Level  Charges").  The Benchmarking
               Process  will take into  consideration  relevant  factors such as
               quality and delivery terms.

7.       INVOICING AND PAYMENT

     7.1. Invoicing.

          WinStar  shall  invoice  Williams  for  all  amounts  due  under  this
          Agreement  prior to the payment dates set forth in Schedule C and on a
          monthly  basis in arrears for all other  charges.  Each invoice  shall
          show such details as  reasonably  requested  by  Williams,  separately
          state the amounts of any taxes collected and include the  calculations
          utilized to establish the charges.

     7.2. Payment Due.

          (a)  Subject  to the other  provisions  of this  Article  7,  invoices
               provided for under Section 7.1 and properly submitted to Williams
               pursuant to this  Agreement  shall be due and payable by Williams
               within  thirty (30) days after  receipt  thereof.  Any amount due
               under  this  Agreement  for  which  a  time  for  payment  is not
               otherwise  specified  shall be due and payable within thirty (30)
               days after receipt of a proper invoice for such amount.

          (b)  To the  extent  a credit  may be due  Williams  pursuant  to this
               Agreement,  WinStar  shall provide  Williams with an  appropriate
               credit against amounts then due and owing; if no further payments
               are due to WinStar,  WinStar  shall pay such  amounts to Williams
               within thirty (30) days.

          (c)  Williams shall make payments provided for under this Article 7 or
               Schedule C by wire transfer of immediately available funds to the
               account or accounts designated by WinStar.  All other payments to
               be made pursuant to this  Agreement may be made by check or draft
               of  immediately   available   funds   delivered  to  the  address
               designated in writing by the other Party (e.g., in a statement or
               invoice) or, failing such designation,  to the address for notice
               to such other Party provided pursuant to Section 12.8.

          (d)  The first invoice  provided under this Agreement shall be due and
               payable within sixty (60) days of the Effective Date.

                                       18
<PAGE>

     7.3. Disputed Charges.

          Williams shall pay undisputed charges when such payments are due under
          this Agreement.  Williams may withhold  payment of particular  charges
          that Williams  disputes in good faith and for which it promptly  gives
          written  notice to WinStar,  stating the details of such dispute.  The
          Parties  shall  promptly  refer such matter to dispute  resolution  in
          accordance  with  Section  11.2.  If Williams  withholds  any disputed
          charges and such charges are  ultimately  determined  to be proper and
          payable to WinStar,  Williams  shall pay such  charges to WinStar plus
          interest at the Prime Rate from the date such charges were  originally
          due until the date such  charges  are  paid.  WinStar  agrees  that no
          payment  dispute  shall be grounds for WinStar to withhold or diminish
          the  quality  or  quantity  of any of the  connectivity  and  services
          provided hereunder.

     7.4. Late Interest.

          If either  Williams or WinStar  fails to make any  payment  under this
          Agreement when due, such amounts shall accrue interest,  from the date
          such payment is due until paid,  including  accrued  interest,  at the
          Prime Rate.

8.   COVENANTS, REPRESENTATIONS AND WARRANTIES

     8.1. Non-Infringement.

          Each Party  represents,  warrants  and  covenants to the other that it
          shall perform its  responsibilities  under this  Agreement in a manner
          that  does  not   infringe,   or   constitute   an   infringement   or
          misappropriation  of, any  Intellectual  Property  Rights of any third
          party.

     8.2. Authorization.

          Each Party represents and warrants to the other that:

          (a)  It has the requisite  corporate power and authority to enter into
               this Agreement and to carry out the transactions  contemplated by
               this Agreement;

          (b)  The execution, delivery and performance of this Agreement and the
               consummation of the  transactions  contemplated by this Agreement
               have been duly  authorized by the requisite  corporate  action on
               the part of such Party;

          (c)  This Agreement  constitutes a legal, valid and binding obligation
               enforceable against such party in accordance with its terms;

          (d)  Its execution of and  performance  under this Agreement shall not
               violate any applicable existing regulations,  rules, statutes, or
               court orders of any local,  state, or federal  government agency,
               court, or body;

          (e)  It is not subject to any  contractual  or other  obligation  that
               would prevent it from entering into this relationship; and

          (f)  It has not offered or provided  any  inducements  in violation of
               law or the  other  Party's  policies  of which it has been  given
               notice, in connection with this Agreement.


                                       19
<PAGE>

     8.3. Wireless Fiber Connectivity.

          Excluding  services  provided by third  parties  other than  WinStar's
          subcontractors,  WinStar  covenants  that the  Williams  T-1s shall be
          designed,   engineered,   installed,   constructed   and  operated  in
          accordance  with  the  specifications  set  forth  in  the  applicable
          services  schedule.  WinStar  further  covenants  that it will use its
          commercially  reasonable efforts under the circumstances to remedy any
          delays, interruptions, omissions, mistakes, accidents or errors in the
          Williams T-1s provided  hereunder and to restore such Williams T-1s to
          compliance with the terms hereof.

     8.4. Disclaimer.

          EXCEPT AS SPECIFICALLY  SET FORTH IN THIS AGREEMENT,  THE PARTIES MAKE
          NO  WARRANTY  TO EACH  OTHER OR ANY  OTHER  ENTITY,  WHETHER  EXPRESS,
          IMPLIED OR  STATUTORY,  AS TO THE  MERCHANTABILITY  OR FITNESS FOR ANY
          PARTICULAR PURPOSE OF ANY WIRELESS FIBER CONNECTIVITY,  WILLIAMS T-1s,
          HUBS,  ANCILLARY  SERVICES OR ANY OTHER SERVICES PROVIDED HEREUNDER OR
          DESCRIBED HEREIN,  OR AS TO ANY OTHER MATTER,  ALL OF WHICH WARRANTIES
          ARE HEREBY EXPRESSLY EXCLUDED AND DISCLAIMED.

9.   INDEMNIFICATION

     9.1. Indemnities by Williams.

          Williams agrees to indemnify, defend and hold harmless WinStar and its
          Affiliates  and  their  respective  officers,  directors,   employees,
          agents,   successors,  and  assigns,  from  any  and  all  Losses  and
          threatened  Losses  arising  from,  in  connection  with,  or based on
          allegations of, any of the following:

          (a)  Williams' failure to observe or perform its duties or obligations
               to third parties (e.g., duties or obligations to subcontractors);

          (b)  Williams'  infringement or  misappropriation  of any Intellectual
               Property Rights of any third party;

          (c)  Williams'  unexcused failure to abide by the terms and conditions
               of the business relationship as mutually agreed to by the Parties
               in writing;

          (d)  The death or  bodily  injury of any  agent,  employee,  customer,
               business  invitee or any other person to the extent caused by the
               tortious conduct of Williams;

          (e)  The damage,  loss or destruction of any real or tangible personal
               property  to  the  extent  caused  by  the  tortious  conduct  of
               Williams;

          (f)  Fines,  penalties  or  other  amounts  payable  due to  Williams'
               violation of applicable laws or regulations; and

          (g)  Any claim,  demand,  charge,  action,  cause of action,  or other
               proceeding  asserted against WinStar but resulting from an act or
               omission of Williams in its capacity as an employer of a person.


                                       20
<PAGE>

     9.2. Indemnities by WinStar.

          WinStar agrees to indemnify, defend and hold harmless Williams and its
          Affiliates  and  their  respective  officers,  directors,   employees,
          agents,   successors,  and  assigns,  from  any  and  all  Losses  and
          threatened  Losses  arising  from,  in  connection  with,  or based on
          allegations of, any of the following:

          (a)  WinStar's failure to observe or perform its duties or obligations
               to third parties (e.g., duties or obligations to its customers);

          (b)  WinStar's   infringement  or   misappropriation  of  Intellectual
               Property Rights of any third party;

          (c)  WinStar's  unexcused failure to abide by the terms and conditions
               of the business relationship as mutually agreed to by the Parties
               in writing;

          (d)  The death or  bodily  injury of any  agent,  employee,  customer,
               business  invitee or any other person to the extent caused by the
               tortious conduct of WinStar;

          (e)  The damage,  loss or destruction of any real or tangible personal
               property to the extent caused by the tortious conduct of WinStar;

          (f)  Fines,  penalties  or  other  amounts  payable  due to  WinStar's
               violation of applicable laws or regulation; and

          (g)  Any claim,  demand,  charge,  action,  cause of action,  or other
               proceeding asserted against Williams but resulting from an act or
               omission of WinStar in its capacity as an employer of a person.

     9.3. Indemnification Procedures.

          With respect to third-party  claims,  the following  procedures  shall
          apply:

          (a)  Promptly  after  receipt  of  notice  of  the   commencement   or
               threatened  commencement of any civil, criminal,  administrative,
               or  investigative  action  or  proceeding  involving  a claim  in
               respect  of  which  the  indemnitee  will  seek   indemnification
               pursuant  to this  Article  9, the  indemnitee  will  notify  the
               indemnitor of such claim in writing.  No failure to so notify the
               indemnitor will relieve the indemnitor of its  obligations  under
               this  Agreement  except  to the  extent  that it can  demonstrate
               damages  attributable  to  such  failure.   Within  fifteen  (15)
               calendar  days  following  receipt  of  written  notice  from the
               indemnitee  relating  to any  claim,  but no later  than ten (10)
               calendar  days  before  the  date  on  which  any  response  to a
               complaint  or  summons is due,  the  indemnitor  will  notify the
               indemnitee in writing if the indemnitor  elects to assume control
               of the  defense  and  settlement  of that  claim  (a  "Notice  of
               Election").

          (b)  If the indemnitor  delivers a Notice of Election  relating to any
               claim within the required notice period,  the indemnitor shall be
               entitled to have sole control over the defense and  settlement of
               such claim; provided that (i) the indemnitee shall be entitled to

                                       21
<PAGE>

               participate in the defense of such claim and to employ counsel at
               its own expense to assist in the handling of such claim, and (ii)
               the indemnitor shall obtain the prior written approval, not to be
               unreasonably  withheld  or  delayed,  of  the  indemnitee  before
               entering  into any  settlement of such claim or ceasing to defend
               against such claim.  After the  indemnitor has delivered a Notice
               of  Election  relating  to  any  claim  in  accordance  with  the
               preceding  paragraph,  the indemnitor  shall not be liable to the
               indemnitee for any legal  expenses  incurred by the indemnitee in
               connection  with the  defense of that  claim.  In  addition,  the
               indemnitor  shall not be required to indemnify the indemnitee for
               any amount paid or payable by the indemnitee in the settlement of
               any claim for which the  indemnitor has delivered a timely Notice
               of  Election  if such  amount was agreed to without  the  written
               consent of the indemnitor.

          (c)  If the indemnitor does not deliver a Notice of Election  relating
               to any claim  within the  required  notice  period,  or ceases to
               defend against the claim,  the indemnitee shall have the right to
               defend the claim in such  manner as it may deem  appropriate,  at
               the cost and  expense of the  indemnitor.  The  indemnitor  shall
               promptly   reimburse  the  indemnitee  for  all  such  costs  and
               expenses.

10. LIABILITY, RISK OF LOSS AND INSURANCE

     10.1. General Intent.

          Subject  to the  specific  provisions  of this  Article  10, it is the
          intent of the  Parties  that each  Party  shall be liable to the other
          Party for any actual damages incurred by the non-breaching  Party as a
          result of the breaching  Party's failure to perform its obligations in
          the manner required by this Agreement.

     10.2. Liability Restrictions.

          (a)  IN NO EVENT,  WHETHER IN CONTRACT OR IN TORT (INCLUDING BREACH OF
               WARRANTY, NEGLIGENCE AND STRICT LIABILITY IN TORT), SHALL A PARTY
               BE LIABLE FOR INDIRECT OR CONSEQUENTIAL,  EXEMPLARY,  PUNITIVE OR
               SPECIAL  DAMAGES  EVEN IF SUCH  PARTY  HAS  BEEN  ADVISED  OF THE
               POSSIBILITY OF SUCH DAMAGES IN ADVANCE.

          (b)  Subject to Subsection (c), below, each Party's total liability to
               the other,  whether in contract or in tort  (including  breach of
               warranty,  negligence  and  strict  liability  in tort)  shall be
               limited to two hundred million dollars ($200,000,000).

          (c)  The  limitation set forth in Subsections  (b),  above,  shall not
               apply  with  respect  to:  (i)  third-party   claims  subject  to
               indemnification  pursuant  to the  Agreement;  (ii)  fees due and
               owing under this  Agreement  at the time of the claim;  and (iii)
               amounts subject of Cover as provided in Section 3.7(b).

          (d)  For the purposes of this  Section  10.2,  all amounts  payable or
               paid to third parties in connection with claims that are eligible
               for  indemnification  pursuant to this Agreement  shall be deemed
               direct damages.

                                       22
<PAGE>

     10.3. Insurance Requirements.

          (a)  During the Term,  WinStar  shall have and  maintain  in force the
               following insurance coverages:

               (i)  Worker's  Compensation  and Employer's  Liability.  Worker's
                    Compensation Insurance in amounts required by applicable law
                    and Employers  Liability Insurance with limits not less than
                    $1,000,000  each  accident.  If work is to be  performed  in
                    Nevada,  North  Dakota,  Ohio,  Washington,  Wyoming or West
                    Virginia,  the party shall  participate  in the  appropriate
                    state fund(s) to cover all eligible  employees and provide a
                    stop  gap  endorsement  for  these  monopolistic  states  in
                    WinStar's Worker's Compensation Insurance Program.

               (ii) Commercial General Liability.  WinStar shall carry broadform
                    general  liability  insurance  coverage for property damage,
                    bodily injury,  personal injury,  contractual  liability and
                    accidental  pollution  legal  liability  with coverage of at
                    least $10,000,000 per occurrence and in the aggregate. Total
                    limits   can   be   attained   by   the   inclusion   of  an
                    Umbrella/Excess Liability policy.

               (iii)Automobile   Liability.   WinStar  shall  carry   automobile
                    liability  insurance  written  on  the  occurrence  form  of
                    policy.  The policy  shall  provide  for  bodily  injury and
                    property  damage  liability  covering  the  operation of all
                    automobiles  used in connection  with  performing  under the
                    Agreement and shall provide  coverage of at least $2,000,000
                    per occurrence.

          (b)  WinStar  shall  cause  its  insurers  to  issue  certificates  of
               insurance  evidencing  that the  coverages  required  under  this
               Agreement are maintained in force. The minimum limits of coverage
               specified herein are not intended, and shall not be construed, to
               limit any liability or indemnity of WinStar under this Agreement.

          (c)  Nothing in this Agreement  shall be construed to prevent  WinStar
               from  satisfying  its  insurance  obligations  pursuant  to  this
               Agreement  under a blanket  policy or policies of insurance  that
               meet or exceed the requirements of this Article.

     10.4. Risk of Loss.

          (a)  Each  Party  shall  promptly  notify  the  other  of any  matters
               pertaining  to any  damage  or  impending  damage  to or  loss of
               Wireless Fiber  Connectivity known to it that could reasonably be
               expected to adversely affect the Wireless Fiber Connectivity.

          (b)  Each Party shall take all  reasonable  precautions  against,  and
               shall  assume  liability  for,  subject  to  the  terms  of  this
               Agreement,  any damage  caused by it to the property of the other
               Party.

          (c)  Neither  Party  shall  use,  or allow  others to use,  equipment,
               technologies,  or methods of operation  that interfere in any way
               with  or  adversely  affect  the  Williams  Connectivity  or  the
               permitted use thereof by Williams,  WinStar or  authorized  third
               parties.


                                       23
<PAGE>

          (d)  Williams  shall not cause or permit any part of the Williams T-1s
               to become subject to any  mechanic's  lien,  materialman's  lien,
               vendor's  lien or any  similar  lien or  encumbrance  whether  by
               operation of law or otherwise.

     10.5. Force Majeure.

          (a)  No  Party  shall  be  liable  for any  default  or  delay  in the
               performance of its obligations under this Agreement if and to the
               extent such default or delay is caused,  directly or  indirectly,
               by fire, flood, lightning, earthquake, elements of nature or acts
               of God, riots, civil disorders,  rebellions or revolutions in any
               country or any other cause beyond the reasonable  control of such
               Party;  provided,  however,  that (i) the non-performing Party is
               without  fault in causing  such  default or delay,  and (ii) such
               default  or delay  could not have been  prevented  by  reasonable
               precautions   and  cannot   reasonably  be  circumvented  by  the
               non-performing  Party  through  the  use  of  alternate  sources,
               workaround plans or other means,  including means contemplated by
               applicable disaster recovery processes or procedures).

          (b)  In such event the  non-performing  Party  shall be  excused  from
               further   performance  or  observance  of  the  obligation(s)  so
               affected for as long as such circumstances prevail and such Party
               continues to use  commercially  reasonable  efforts to recommence
               performance  or  observance   whenever  and  to  whatever  extent
               possible  without delay.  Any Party so delayed in its performance
               shall  immediately  notify the other  Party by  telephone  (to be
               confirmed  in  writing  within  two  (2)  business  days  of  the
               inception of such delay) and  describe at a  reasonable  level of
               detail the circumstances  causing such delay. The  non-performing
               party will provide the other party prompt  written  notice of the
               cessation or termination of the force majeure event.

11.  REMEDIES AND DISPUTE RESOLUTION

     Any  dispute  between  the  Parties  arising  out of or  relating  to  this
     Agreement, including with respect to the interpretation of any provision of
     this Agreement and with respect to the  performance by Williams or WinStar,
     shall be resolved as provided in this Article 11.

     11.1. Cumulative Nature.

          Except as otherwise  expressly  provided herein, all remedies provided
          for in this  Agreement  shall be cumulative and in addition to and not
          in lieu of any other  remedies  available  to either  Party at law, in
          equity or otherwise.

     11.2. Informal Dispute Resolution.

          (a)  Prior to the initiation of formal dispute  resolution  procedures
               (i.e.,  arbitration),  the Parties shall first attempt to resolve
               their  dispute  at the  senior  manager  level.  If that level of
               dispute  resolution is not successful,  the Parties shall proceed
               informally, as follows:

                                       24
<PAGE>

               (i)  Upon the written  request of either Party,  each Party shall
                    appoint a designated  representative  who does not otherwise
                    devote  substantially  full time to  performance  under this
                    Agreement,  whose task it will be to meet for the purpose of
                    endeavoring to resolve such dispute.

               (ii) The  designated  representatives  shall meet as often as the
                    Parties  reasonably  deem  necessary  in order to gather and
                    furnish  to the other all  information  with  respect to the
                    matter in issue that the Parties  believe to be  appropriate
                    and  germane  in  connection   with  its   resolution.   The
                    representatives  shall  discuss  the  problem and attempt to
                    resolve the  dispute  without  the  necessity  of any formal
                    proceeding.

               (iii)During the course of  discussion,  all  reasonable  requests
                    made   by  one   Party   to   another   for   non-privileged
                    non-confidential  information  reasonably  related  to  this
                    Agreement  shall be honored so that each of the  Parties may
                    be fully advised of the other's position.

               (iv) The specific format for the discussions shall be left to the
                    discretion of the designated representatives.

          (b)  Prior to instituting formal  proceedings,  the Parties will first
               have their chief executive  officers meet to discuss the dispute.
               This  requirement  shall  not  delay  the  institution  of formal
               proceedings  past any statute of  limitations  expiration  or for
               more than fifteen (15) days.

          (c)  Subject to Subsection (b), formal  proceedings for the resolution
               of a dispute may not be commenced until the earlier of:

               (i)  The designated representatives concluding in good faith that
                    amicable  resolution  through  continued  negotiation of the
                    matter does not appear likely; or

               (ii) Thirty  (30)  days  after the  initial  written  request  to
                    appoint a designated  representative  pursuant to Subsection
                    (a),   above,   (this   period   shall  be   deemed  to  run
                    notwithstanding any claim that the process described in this
                    Section 11.2 was not followed or completed).

          (d)  This  Section 11.2 shall not be construed to prevent a Party from
               instituting,  and a Party  is  authorized  to  institute,  formal
               proceedings  earlier to avoid the  expiration  of any  applicable
               limitations  period,  or to  preserve  a superior  position  with
               respect to other creditors or as provided in Section 11.6(a).

     11.3. Arbitration.

          If the  Parties  are unable to resolve a dispute  as  contemplated  by
          Section  11.2,  and that  dispute  is not  subject  to 11.6(a) of this
          Agreement,  then such dispute  shall be  submitted  to  mandatory  and
          binding  arbitration  at the election of either Party (the  "Disputing
          Party") pursuant to the following conditions:

          (a)  Selection of  Arbitrator.  The  Disputing  Party shall notify the
               American  Arbitration  Association  ("AAA") and the other  Party,
               describing in reasonable  detail the nature of the dispute,  (the

                                       25
<PAGE>

               "Dispute  Notice") and shall  request that the AAA furnish a list
               of five (5) possible arbitrators who have substantial  experience
               in the telecommunications industry. Each Party shall have fifteen
               (15) days to reject two (2) of the proposed arbitrators.  If only
               one individual has not been so rejected,  that person shall serve
               as arbitrator;  if two (2) or more  individuals  have not been so
               rejected,   the  AAA  shall  select  the  arbitrator  from  those
               individuals.

          (b)  Conduct of  Arbitration.  The arbitrator  shall allow  reasonable
               discovery in the forms  permitted  by the Federal  Rules of Civil
               Procedure,  to the  extent  consistent  with the  purpose  of the
               arbitration.  The arbitrator  shall have no power or authority to
               amend or  disregard  any  provision  of this  Section 11.3 or any
               other provision of this Agreement. In particular,  the arbitrator
               shall not have the  authority  to exclude the right of a Party to
               terminate this  Agreement when a Party would  otherwise have such
               right.  The arbitration  hearing shall be commenced  promptly and
               conducted expeditiously.

          (c)  Replacement  of Arbitrator.  Should the  arbitrator  refuse or be
               unable to proceed with  arbitration  proceedings as called for by
               this Section,  such arbitrator  shall be replaced and a rehearing
               shall  take  place  in  accordance  with the  provisions  of this
               Section.  In such case, the replacement for the arbitrator  shall
               be  either  selected  by the  AAA  from  the  original  group  of
               potential  arbitrators  that were not rejected by the Parties or,
               if there are no such arbitrators available, selected by repeating
               the process of selection described in Subsection (a), above.

          (d)  Findings and Conclusions.  The arbitrator rendering judgment upon
               disputes between Parties as provided in this Section shall, after
               reaching  judgment  and  award,  prepare  and  distribute  to the
               Parties a writing describing the findings of fact and conclusions
               of law  relevant  to such  judgment  and award.  The award of the
               arbitrator  shall  be  final  and  binding  on the  Parties,  and
               judgment   thereon  may  be  entered  in  a  court  of  competent
               jurisdiction.

          (e)  Place of Arbitration  Hearings.  Arbitration  hearings  hereunder
               shall  be held in  Chicago,  Illinois.  If the  Parties  mutually
               agree, arbitration hearings may be held in another location.

          (f)  Time of the Essence. The arbitrator is instructed that time is of
               the  essence  in  the  arbitration   proceeding,   and  that  the
               arbitrator  shall have the right and authority to issue  monetary
               sanctions  against  either of the  Parties  if, upon a showing of
               good cause,  that Party is unreasonably  delaying the proceeding.
               Recognizing  the express desire of the Parties for an expeditious
               means of dispute resolution,  the arbitrator shall limit or allow
               the Parties to expand the scope of discovery as may be reasonable
               under the circumstances.

     11.4. Termination.

          A Party shall not be in material  breach of this Agreement  unless and
          until the other Party  provides  it written  notice of default and the
          non-performing  party has failed to cure within thirty (30) days after
          receipt of such notice.  Any event of default may be waived in writing
          at the non-defaulting  Party's option.  Upon the failure of a Party to
          timely cure its material breach  hereunder  within the applicable cure

                                       26
<PAGE>


          period, the non-defaulting Party shall have the right to (i) terminate
          this Agreement or (ii) subject to the terms of this Article 11, pursue
          any legal  remedies it may have under  applicable law or principles of
          equity relating to such breach.

     11.5. Suspension of Service.

          If  Williams  does not make any  undisputed  payment  of at least  One
          Hundred Thousand Dollars  ($100,000) within thirty days of the payment
          due date,  WinStar may suspend  service to all Williams T-1s upon five
          (5) days' prior  written  notice if Williams does not cure within such
          period.  If such non-payment  continues for more than thirty (30) days
          after  receipt  of such  notice,  WinStar  shall  have  the  right  to
          terminate this Agreement.

     11.6. Litigation.

          (a)  Immediate  Injunctive  Relief.  The  only  circumstance  in which
               disputes  between  the  Parties  shall  not  be  subject  to  the
               provisions  of Sections  11.2 and 11.3 is where a Party,  in good
               faith,  determines  that a temporary  restraining  order or other
               injunctive relief is its only appropriate and adequate remedy. If
               a Party seeks immediate injunctive relief and does not prevail in
               substantial  part,  that Party shall pay the other  Party's costs
               and  attorneys'  fees to the extent  incurred in responding to or
               challenging the request for immediate injunctive relief.

          (b)  Jurisdiction.  The  Parties  consent to the  jurisdiction  of the
               courts of the State of New York and to jurisdiction  and venue in
               the United States District Court for the Southern District of New
               York for all  litigation  that may be brought with respect to the
               terms of, and the transactions and relationships contemplated by,
               this Agreement.  The Parties further consent to the  jurisdiction
               of any state court  located  within a district  that  encompasses
               assets of a Party  against which a judgment has been rendered for
               the  enforcement  of such judgment or award against the assets of
               such Party.

          (c)  Governing Law. This Agreement and  performance  under it shall be
               governed  by and  construed  in  accordance  with the laws of the
               State of New York without regard to its choice of law principles.

     11.7. Continued Performance.

          Each Party agrees to continue  performing its  obligations  under this
          Agreement while any dispute is being resolved except to the extent the
          issue in dispute precludes performance (dispute over payment shall not
          be deemed to preclude performance except as provided in Section 11.5).

12.  GENERAL

     12.1. Binding Nature and Assignment.

          (a)  This Agreement shall accrue to the benefit of and be binding upon
               the Parties hereto and any purchaser or any successor entity into
               which  either Party has been merged or  consolidated  or to which
               either Party has sold or transferred all or substantially  all of
               its assets.


                                       27
<PAGE>

          (b)  Neither  Party  may,  or shall  have the  power to,  assign  this
               Agreement or delegate such Party's obligations  hereunder without
               the prior written consent of the other, except to:

               (i)  An entity  that  acquires  all or  substantially  all of the
                    assets of such Party,

               (ii) Any Affiliate,

               (iii) A successor in a merger or acquisition of either Party, or

               (iv) In connection with any financing.

     12.2. Entire Agreement.

          This  Agreement,  including any attached  Schedules,  constitutes  the
          entire  agreement  between  the  Parties  with  respect to the subject
          matter in this Agreement, and supersedes all prior agreements, whether
          written or oral, with respect to the subject matter  contained in this
          Agreement.

     12.3. Tariff.

          WinStar  acknowledges  that  this  is  a  private  non-common  carrier
          agreement and that any  incorporation of WinStar tariff  provisions is
          done for the convenience of the Parties.

     12.4. Consents.

          As  between  the  parties,  Williams  shall  be  responsible  for  all
          arrangements with copyright  holders,  music licensing  organizations,
          performers'   representatives   or   other   parties   for   necessary
          authorizations,  clearances or consents  with respect to  transmission
          contents.

     12.5. Restriction of Transmissions.

          Williams  will not transmit  content that violates  applicable  law or
          carries  an  unreasonable  risk  of  leading  to  criminal,  civil  or
          administrative  proceedings  or  investigations  against  Williams  or
          WinStar.

     12.6. Use and Ownership.

          Neither Party shall have any right, title or interest to the equipment
          installed by the other Party.

     12.7. Non-Solicitation.

          Neither  Party  shall  directly  or  indirectly  solicit  the  other's
          employees or contractors  without the other Party's  written  consent,
          which shall not be unreasonably withheld.


                                       28
<PAGE>

     12.8. Notices.

          All  notices,   requests,   demands,  and  determinations  under  this
          Agreement (other than routine operational communications), shall be in
          writing  and shall be deemed  duly given (i) when  delivered  by hand,
          (ii) one (1) business  day after being given to an express,  overnight
          courier  with a system  for  tracking  delivery,  (iii)  when  sent by
          confirmed facsimile with a copy delivered  thereafter by another means
          specified in this  Section,  or (iv) four (4) business  days after the
          day of mailing,  when mailed by United States  registered or certified
          mail,  return receipt  requested,  postage  prepaid,  and addressed as
          follows:

          If to WinStar:                    If to Williams:
            WinStar Wireless, Inc.            Williams Communications, Inc.
            230 Park Avenue                   One Williams Center, Suite 26-5
            New York, NY  10169               Tulsa, Oklahoma  74172
            Attn:  EVP, General Counsel       Attn:  Contract Administration
            Facsimile:  212/922-1637          Facsimile:  918/573-6578

          With a copy to:                   With a copy to:
            WinStar Wireless, Inc.            Williams Communications, Inc.
            7799 Leesburg Pike                One Williams Center, Suite 4100
            Falls Church, Virginia 22043      Tulsa, Oklahoma  74172
            Attn:  VP, Commercial and         Attn:  General Counsel
              Legal Operations
            Facsimile:  703/288-6647          Facsimile:  918/573-3005


          A Party may from time to time  change  its  address  or  designee  for
          notification  purposes by giving the other prior written notice of the
          new  address  or  designee  and the date  upon  which  it will  become
          effective.

     12.9. Counterparts.

          This Agreement may be executed in several  counterparts,  all of which
          taken  together  shall  constitute  one single  agreement  between the
          Parties hereto.

     12.10. Relationship of Parties.

          Each  Party,  in  performing  hereunder,  is acting as an  independent
          contractor,  and such Party's personnel (including its subcontractors)
          shall not be considered or  represented  as employees or agents of the
          other  Party.  Neither  Party  is an  agent  of the  other  and has no
          authority  to  represent  that  Party  as to any  matters,  except  as
          expressly authorized in this Agreement.

     12.11. Severability.

          If any provision of this Agreement  conflicts with the law under which
          this  Agreement is to be  construed  or if any such  provision is held
          invalid  by an  arbitrator  or a  court  with  jurisdiction  over  the
          Parties,  such provision  shall be deemed to be restated to reflect as
          nearly  as  possible  the  original   intentions  of  the  Parties  in
          accordance  with applicable law. The remainder of this Agreement shall
          remain in full force and effect.


                                       29
<PAGE>

     12.12. Reasonableness, Consents and Approval.

               (a)  Where  this   Agreement   requires  a  Party  to  assist  or
                    cooperate,  such  requirement  shall not be  interpreted  to
                    require materially more than a commercially reasonable level
                    of effort (i.e.  the standard  applicable  will not be "best
                    efforts" or "exhausting all available means").

               (b)  Except  where  expressly  provided  as  being  in  the  sole
                    discretion   of  a   Party,   where   agreement,   approval,
                    acceptance,  consent,  or similar  action by either Party is
                    required  under this  Agreement,  such  action  shall not be
                    unreasonably  delayed or  withheld.  An  approval or consent
                    given by a Party under this Agreement  shall not relieve the
                    other  Party  from  responsibility  for  complying  with the
                    requirements of this Agreement, nor shall it be construed as
                    a waiver of any rights under this  Agreement,  except as and
                    to the extent otherwise  expressly provided in such approval
                    or consent.

     12.13. Waiver of Default.

          No waiver or  discharge  hereof  shall be valid  unless in writing and
          signed by an authorized representative of the Party against which such
          amendment,  waiver, or discharge is sought to be enforced.  A delay or
          omission by either  Party  hereto to exercise any right or power under
          this Agreement shall not be construed to be a waiver thereof. A waiver
          by  either  of the  Parties  hereto  of any  of  the  covenants  to be
          performed by the other or any breach thereof shall not be construed to
          be a waiver of any succeeding  breach thereof or of any other covenant
          herein contained.

     12.14. Survival.

          No  termination   of  this  Agreement   shall  affect  the  rights  or
          obligations of any Party with respect to any other  provisions of this
          Agreement that contemplate performance or observance subsequent to any
          termination or expiration of this Agreement.

     12.15. Public Disclosures.

          All media  releases,  public  announcements,  and  public  disclosures
          relating to this  Agreement or the subject  matter of this  Agreement,
          including  promotional  or  marketing  material,   but  not  including
          announcements intended solely for internal distribution or disclosures
          to the extent required to meet legal or regulatory requirements, shall
          be  coordinated  with and shall be subject to approval by both Parties
          prior to release.

     12.16. Third Party Beneficiaries.

          Except as otherwise  provided in this Agreement,  this Agreement shall
          not be  deemed  to  create  any  rights  in third  parties,  including
          suppliers and customers of a Party,  or to create any obligations of a
          Party to any such third parties.

     12.17. Amendment.

          (a)  This  Agreement  shall  not be  modified,  amended  or in any way
               altered  except  by an  instrument  in  writing  signed  by  both
               Parties.


                                       30
<PAGE>

          (b)  Unless otherwise expressly  permitted in this Agreement,  WinStar
               shall not make any changes to the Exhibits or Schedules  attached
               hereto that may have a material adverse impact on the performance
               or usability of Williams  Connectivity  without  Williams'  prior
               written consent.

     12.18. Order of Precedence.

          In the event of a conflict,  this Agreement shall take precedence over
          the Schedules attached hereto, and the Schedules shall take precedence
          over their attached Exhibits.

          This  order of  precedence  may be  modified  in a  subsequently-added
          Schedule or Exhibit if this  modification  is explicitly  noted in the
          corresponding amendment instrument.

     12.19. Interpretation.

          (a)  Terms other than those defined in this  Agreement  shall be given
               their  plain  English  meaning,  and those  terms,  acronyms  and
               phrases   known  in  the   telecommunications   and   information
               technology services industries shall be interpreted in accordance
               with their generally known meanings. Unless the context otherwise
               requires,  words  importing  the singular  include the plural and
               vice-versa.

          (b)  References to "Article,"  "Section,"  "Subsection" and "Schedule"
               mean references to an article, section, subsection or schedule of
               this Agreement,  as appropriate,  unless  otherwise  specifically
               stated.

          (c)  The article and section  headings in this  Agreement are intended
               to be  for  reference  purposes  only  and  shall  in no  way  be
               construed to modify or restrict any of the terms or provisions of
               this Agreement.

          (d)  The words "include," "includes" and "including," when following a
               general  statement  or term,  are not to be construed as limiting
               the general  statement or term to any specific item or matter set
               forth or to similar  items or matters,  but rather as  permitting
               the general statement or term to refer also to all other items or
               matters that could reasonably fall within its broadest scope.

     12.20. Covenant of Good Faith.

          Each Party  agrees that,  in its  respective  dealings  with the other
          Party under or in connection with this Agreement,  it will act in good
          faith.


IN WITNESS  WHEREOF,  this  Agreement  has been  executed  and  delivered by the
undersigned  officers,  thereunto duly authorized,  as of the date first written
above.

<TABLE>
<S>                                                            <C>  
WINSTAR WIRELESS, INC.                                          WILLIAMS COMMUNICATIONS, INC.




               /s/ Timothy R. Graham                                            /s/ Frank Semple
By:           --------------------------------------------      By:            ----------------------------------------
               Timothy R. Graham                                                Frank Semple
Name:         --------------------------------------------      Name:          ----------------------------------------
               Vice President                                                   President, Williams Network
Title         --------------------------------------------      Title:         ----------------------------------------
               December 17, 1998                                                December 17, 1998
Date:         --------------------------------------------      Date:          ----------------------------------------

</TABLE>

<PAGE>
                         Schedule A - Scope and Services

                           WinStar Network Description
1.      Current WinStar Wireless Topology, Network Building Blocks and Elements.

         Set forth below is a general description of WinStar's network:

1.1.     Network Building Blocks.


          The current WinStar network consists of independent voice and data
          networks. The voice network is entirely time-division multiplexed
          ("TDM") based while the data network is a combination of TDM and
          packet technologies. The network elements of the voice and data
          networks are being physically collocated to afford all of WinStar's
          customers the opportunity to access all products and services in a
          seamless manner. The WinStar network comprises the following major
          building blocks:

          (a)  Central Offices. The Central Office is the service node for all
               voice and data services. It houses a voice switch, an ATM switch,
               frame relay switch, milliwave radios, transmission gear, host
               loop carrier equipment, distribution frames and all necessary
               power, network management devices, data service gateways, HVAC
               and environmental controls. Many Central Offices also serve as
               Hubs, as defined below.

          (b)  Hubs. A "Hub" is a Lit Building that serves as an access node in
               a particular WinStar Target Market that contains milliwave
               radios, host loop carrier equipment, transmission gear,
               distribution frames, network management devices and related
               necessary power, HVAC and environmental controls. In implementing
               a Hub, WinStar seeks to have an average of ten (10) buildings
               with line of sight and in range of the Hub.

          (c)  Lit Buildings. A Lit Building that houses milliwave radios,
               remote loop carrier equipment, intra-building connectivity
               facilities and/or gear to reach WinStar's customer demarcation
               point and all necessary power. A Lit Building can also serve as a
               Hub in a reduced configuration.

          (d)  Collocation Sites. WinStar physically or virtually collocates
               subscriber loops and transmission/mux gear with LECs, IXCs and
               CAPs. WinStar uses LECs and CAPs to access unbundled loops and
               T1/T3 facilities for the provisioning of service to WinStar
               customers.

          (e)  Data-Only Points. In some markets, there may be WinStar services
               deployed that are not built around a 5ESS anchor. These markets
               may also require a Central Office environment with engineered
               access, power, transmission and switching.

<PAGE>

1.2.     Topology.


          The network topology currently consists of a centralized switching
          platform that provides all of the features, services and switching
          functionality for all customers in a particular network serving area.
          Each switch delivers services to and from WinStar customers through
          interconnect facilities to and from the LEC, IXCs and Internet Peering
          Points to which WinStar has connections. Today, Switches may connect
          to Hubs in both a hub-and-spoke and ring topology. Hubs connect to Lit
          Buildings in a hub-and-spoke topology.

1.3.     Switching.


          The voice network today consists of Lucent 5ESS switches, typically
          deployed one per city and operated as the centralized switching
          platform for the entire market. All switches provide local service
          through interconnect arrangements with the incumbent LEC. All WinStar
          switches provide long distance service to WinStar local customers and
          most switches provide long distance services to WinStar switched
          access long distance customers. The data network consists of Newbridge
          36170 ATM switches and Cascade 9000 frame relay switches in the
          Central Office.

1.4.     Interconnect.


          The Interconnect facilities are the physical connections from
          WinStar's switches to other carrier networks for the provisioning of
          services to WinStar customers. These facilities connect to the LECs,
          IXCs, Internet Peering Points, carrier hotels (locations with a large
          concentration of carrier POPs) and CAPs. The capacity of the
          interconnect facilities varies from T-1 to multiple OC-12 and OC-48.
          The interconnect network can consist of any component of the
          transmission facilities, as described below.

1.5.     Transmission.


          The transmission network provides connections from the Switch to the
          Hubs, Collocation sites and Switches in other WinStar network serving
          areas. The capacity of the transmission facilities varies from T-1 to
          multiple OC-12 and OC-48. The transmission network can consist of:

          (a)  Leased telco facilities on copper or fiber;

          (b)  Point-to-point milliwave radio facilities operating on
               WinStar-licensed radio frequency bands; or

          (c)  Fiber that has been procured through long-term IRUs and uses
               optronics owned and operated by WinStar.

1.6.     Access.


          The access network provides connections from Lit Buildings to Hubs and
          switches. Although fiber or other telco facilities may be used, the
          preferred and most widely used access medium is Wireless Fiber
          Connectivity. In these cases, the access used is dedicated, TDM-based,
          point-to-point milliwave radio facilities operated on primarily the 28
          and 38 GHz bands licensed by WinStar. WinStar does use other radio
          bands if and when they are available and appropriate. The geographical
          coverage areas, as defined and authorized by the FCC where WinStar has
          38 GHz licenses, are called Licensed Serving Areas ("LSAs"). The
          geographical coverage areas authorized by the FCC and where WinStar
          has 28 GHz licenses are called Basic Trading Areas ("BTAs").


<PAGE>

1.7.     CTE/CPE.


          The CTE/CPE employed today consists of channel banks, digital loop
          carrier equipment, DSUs, routers, bridges and hubs. Most Lit Buildings
          have loop carrier equipment deployed as a matter of course to
          provision voice services. Other devices are selected and deployed at
          the time of customer order based on the services to be offered to the
          customer.

2.       WinStar Network Services

         WinStar has entered into this Agreement solely for the provisioning of
         wireless local loop access to Williams. However, the Winstar network
         does offer a wide range of additional communications services which may
         be of interest to Williams in the future including: local voice, long
         distance voice, network transport, Internet services, LAN/WAN
         integration, and other professional services. This functionality is
         outlined below for informational purposes only.

2.1.     Domestic Voice Functionality.


          Voice service products may or may not be tariffed. Tariffed services
          must interoperate and interwork with other like tariffed services, if
          offered, from incumbent carriers in a service area. On a
          service-by-service basis, non-tariffed enhanced services may or may
          not interwork or interoperate with other non-tariffed like offerings
          in a service area. Such products include: Basic and Enhanced Voice,
          CLASS, Operator services, Directory services, 911 services, Local
          switching (Class 5), AIN, LD switching (Class 4) and IN, Least Cost
          Routing, DXC Access integration, 800/888 services, Information/900
          services, Centrex, ISDN, Call center outsourcing services,
          Network-based voicemail, Voice conference services, Voice network
          design, outsourcing services, CPE and PBX CTI.

2.2.     Domestic Data Functionality.


          Data service products may or may not be tariffed. Tariffed services
          must interoperate and interwork with other like tariffed services, if
          offered, from incumbent carriers in a service area. On a service by
          service basis, non-tariffed enhanced services may or may not interwork
          or interoperate with other non-tariffed like offerings in a service
          area. Such products include: Point to Point Connectivity, Internet
          Access, UseNet groups, Web hosting, e-commerce, VPN connectivity,
          Email, Network Notes services, IP telephony/fax, Multimedia and video,
          IP multimedia conferencing services, CPE, WAN professional services,
          LAN professional services, security services, E Commerce, Web/Intranet
          systems integration, Private Peering, Customer Network Management,
          TCP/IP, Frame Relay and X.25 / SNA integration.


<PAGE>

3.       Planned WinStar Network Evolution.

         WinStar anticipates certain changes in the topology of the network as
         new technologies and network elements may evolve. While this section
         sets forth the anticipated network evolution, the final architecture
         will depend on future requirements, cost and availability of access and
         transmission bandwidth, technologies and services.

         It is WinStar's intention to merge voice and data services into common
         local infrastructure where these service share common "Next Generation"
         network elements. In addition, a common inter-city transport network is
         required to support combined voice and data functionality. This
         integrated metropolitan and national network will employ technology as
         determined by WinStar.

3.1.     Switching.


          The network today consists of a centralized switching topology
          connected to access nodes via transmission facilities. This topology
          is expected to gradually evolve to a more distributed switching
          architecture whereby many former access nodes become service nodes.

          (a)  The building blocks formerly referred to as switches, and perhaps
               several of the Hubs, will become Integrated Core Service Nodes
               ("ICSNs"). The ICSN may contain many of the same network elements
               as it did before, however it will now be configured and
               integrated in a manner such that the provisioning of service and
               utilization of transmission and access facilities will become
               more efficient and seamless relative to the voice, data and video
               services provided. Also, it is anticipated that there will be
               more than a single ICSN in a particular market, which will offer
               additional efficiencies via more localized, multiple interconnect
               facilities to other carrier networks.

          (b)  Hubs that do not qualify as ICSNs because of traffic density or
               operating costs will become Integrated Edge Service Nodes
               ("IESNs"). The IESN will be much like the ICSN, but it will not
               have direct interconnect facilities to other carrier networks and
               the switching functionality will be less sophisticated.

3.2.     Interconnect.


          The interconnect facilities defined in the previous section are
          expected to evolve in three major ways:

          (a)  Facilities will migrate from hard partitioning for voice and data
               services to clear pipes over which voice and data traffic will be
               transported via packet technologies;

          (b)  With the addition of new, distributed service nodes, there will
               be multiple interconnection points to other carrier networks from
               the numerous ICSNs as opposed to a single interconnect point with
               the centralized switching architecture; and


<PAGE>

          (c)  The Interconnect facilities will continue to use the mediums as
               previously described but the use of WinStar fiber procured
               through long-term IRUs and using optronics owned and operated by
               WinStar is expected to increase. Also, it is anticipated that
               long-term trends in bandwidth requirements and increased WinStar
               market share will drive the capacity of these facilities much
               higher than today.

3.3.     Transmission.


          Fundamental to advanced services is the deployment of optical
          networking solutions in the network (locally and nationally),
          switching and restoration capabilities for multiple optical rings, and
          the appropriate terminating equipment required to deliver services to
          WinStar customers. Network bandwidth requirements are expected to
          increase to multiple OC-192s in the coming years in order to support
          rapidly expanding Internet Protocol (IP) traffic. IP traffic is
          expected to be pervasive in the local loop, over radio facilities and
          in the long haul network. The Transmission network is expected to
          evolve in the following ways:

          (a)  The topology will migrate from a hub-and-spoke topology to a ring
               and/or mesh topology where it is determined to be the most
               cost-effective and efficient solution;

          (b)  The physical provisioning that is required today will be greatly
               reduced and gradually replaced by logical and virtual
               connections; and

          (c)  The transmission facilities will continue to use the mediums as
               previously described but the use of WinStar fiber procured
               through long-term IRUs and using optronics owned and operated by
               WinStar is expected to increase dramatically. Also, it is
               anticipated that long-term trends in bandwidth requirements and
               increased WinStar market share will drive the capacity of these
               facilities much higher than today. 

3.4. Access.

          The Access network is expected to evolve in the following ways:

          (a)  The access network medium will become increasingly more dependent
               on wireless vs. leased telco facilities as the number of Lit
               Building and Hub leases increases which in turn will greatly
               increase the number of constructed wireless access points;

          (b)  The wireless access medium will allow dynamic allocation of
               bandwidth over the air interfaces via packet technologies;

          (c)  Increased bandwidth requirements and new technologies for
               advanced services will cause the average wireless bandwidth per
               building to increase from 8xT1 and DS-3 bandwidth to OC-3 speeds
               and higher;


<PAGE>

          (d)  New point-to-multipoint radio technologies will become
               commercially available and offer "sharing" or "trunking" of
               WinStar's wireless spectrum to multiple Lit Buildings
               simultaneously with an air interface that has evolved from TDM to
               packet technologies. The Access network will become a hybrid
               wireless network consisting of a combination of dedicated
               high-capacity point-to-point radio and point-to-multipoint radio
               technologies; and

          (e)  As WinStar's business needs arise, WinStar may attempt to acquire
               bandwidth in different portions of the wireless spectrum, which
               will create opportunities for new Access topologies and schemas.

3.5.     CTE/CPE.


          The CTE/CPE employed today is expected to change dramatically to
          integrated edge devices and customer premises equipment, which will
          provide flow-through logical and virtual provisioning as a much more
          graceful solution to the current challenges of physical provisioning
          of broadband integrated voice, data and video services. These edge
          devices, unlike today's solutions, will be deployed as a matter of
          course based on the expectation that cost-effective solutions will be
          developed to justify doing so.

4.       WIRELESS FIBER CONNECTIVITY

4.1.     General Description.


          This section outlines the scope of work for WinStar to provide
          Williams T-1s over Wireless Fiber. 

          (a)  Design.


               The Williams T-1s will be implemented using a milliwave radio
               system that consists of two (2) separate terminals operating in
               the same frequency band on complementing transmit and receive
               frequencies. Each WinStar milliwave radio system consists of an
               antenna and mount, outdoor unit ("ODU"), indoor unit ("IDU") and
               IDU-to-ODU interconnect cable. Each radio system connects a Hub
               and a Lit Building via 38 Ghz circuits in a point-to-point or
               -multipoint configuration. Wireless Fiber links are engineered to
               perform at 99.999% availability using RF engineering tools and
               applicable standards for atmospheric conditions. The Hub, in
               turn, connects to a WinStar metropolitan area network ("MAN"),
               which, in turn, connects to the local WinStar point of presence
               in a given metropolitan area.


               The ODU is designed to be mounted either directly to the antenna
               on an antenna mount assembly or, depending on the model, remotely
               from the antenna. The IDU is designed to be mounted in a standard
               nineteen inch (19") EIA relay rack or in an enclosed lockable
               cabinet in a designed secure location. Prior to the installation
               of a WinStar milliwave radio system, the proposed installation
               site shall be site surveyed, engineered and documented.


<PAGE>

          (b)  Network Architecture.

               (i)  Hubs and Lit Buildings communicate via multiple DS3/DS1
                    radio links in the 38-40 Ghz portion of the spectrum. The
                    Hubs function as concentrators for these milliwave links,
                    providing DS3 or DS1 service for Lit Buildings within the
                    Hub service area. The traffic from the Lit Buildings will be
                    bundled into multiple DS3 links over a fiber SONET ring
                    backbone, or connected by lower frequency radio shots (i.e.,
                    18 and 23 Ghz currently and 6 and 11 Ghz in the future).

               (ii) The network architecture features Lit Buildings as customer
                    access points for traffic, with Hubs transmitting and
                    receiving traffic from Lit Buildings via milliwave links.
                    Hubs concentrate, transmit and receive that traffic over
                    fiber links to central office switch sites, other Hubs and
                    points of collocation (each a point of presence).

4.2.     Equipping and Commissioning of Qualified Buildings.


          The following outlines the scope of work required to "light" a
          Qualified Building.

          (a)  Before installing a radio terminal, WinStar must perform the
               following activities:

               (i)  Perform a site survey to assess installation requirements,

               (ii) Prepare radio path calculations for terminal parameter
                    settings,

               (iii) Prepare radio common space for installation as required,

               (iv) Install electrical power per specifications,

               (v)  Install cabinet(s) and radio(s) with all necessary
                    x-connects, mux equipment if applicable and power
                    distribution,

               (vi) Install waterproof sleeves at the building's roof-to
                    interior penetration point,

               (vii) Assemble and install the antenna mount in the position
                    identified during the construction survey to ensure line of
                    sight to the Hub facility,

               (viii) Ground mount per local practice,

               (ix) Install coaxial cable (plenum rated, if required) between
                    common equipment location and the antenna mount,

               (x)  Identify inside wiring distribution pathways, and

               (xi) Core drill verticals if required and sleeve.


<PAGE>

          (b)  Typically, WinStar installs five (5) coaxial cables from the roof
               mount to the interior equipment location, four (4) dedicated to
               radio, and one (1) spare. The maximum allowable IDU-to-ODU cable
               length is one thousand feet (1,000').

          (c)  WinStar shall install lightning arrestor/surge protectors near
               the point of building penetration. WinStar will obey local codes
               or building management rules that require conduit or other
               deviation from standard practices. WinStar shall verify an
               internal distribution path for inside wiring through telco risers
               and establish cable paths sufficient for vertical distribution as
               identified by the Site Survey.

          (d)  Lit Building Power Requirements


               WinStar will use the Reltec/Lorain MZ-60 rectifier
               battery-backed-up system as the standard power supply for Lit
               Buildings. Such a -48VDC power system shall supply between 10 and
               60 amps DC. The system shall accept various AC feeds depending on
               site requirements.

               (i)  WinStar shall determine the building rectifier and AC power
                    requirements during the preliminary site evaluation phase.
                    WinStar shall install one (1) 120 or 240 VAC, 20-50 amp
                    single phase circuit per MZ-60 power plant. The circuit
                    shall terminate into a NEMA L5-20-50 Twistlock female
                    connector and shall be mounted in an electrical outlet box.
                    The male connector shall be supplied on a pre-manufactured
                    power cord for the rectifier assembly.

               (ii) WinStar shall install one (1) 120 VAC, 20 amp single-phase
                    circuit. The circuit shall terminate into a NEMA L5-20
                    Twistlock female connector, mounted in an electrical outlet
                    box. This Circuit shall be used for the internal AC outlet
                    strip, which shall host the cabinet fan assembly power plant
                    requirement. It may also supply power to future equipment,
                    test equipment and PCs that maintain the network. The male
                    connector for the cord of the AC outlet strip shall be
                    changed to a NEMA L5-20 Twistlock Male Connector. Such
                    connector shall be assembled during the equipment
                    reconfiguration. WinStar shall provision one (1) 20 amp
                    circuit for every three (3) cabinets on a site. The AC
                    outlet strips may be connected in series, in-between
                    cabinets.

               (iii) WinStar shall install the outlet boxes no lower than
                    eighty-four inches (84") from the base of the floor and not
                    more than eight feet (8') from the cabinet location.


<PAGE>

4.3.     Test, Turn-up and Certification.


          Upon completion of the installation, WinStar will perform testing,
          turnup and certification of the radio link per the standards in
          Exhibit A-4 to ensure that the link meets WinStar specifications, the
          link has been documented appropriately and can be monitored from the
          WinStar Network Management Center. At this point the building is ready
          for provisioning. 

4.4. Provisioning of Access to Lit Buildings.

          Upon receipt of an order for Williams facility, WinStar will:

          (a)  Complete order entry into the provisioning system,

          (b)  A provisioner will complete circuit design and create a Circuit
               Layout Record (CLR) which represents the cross-connects and
               assignments for the circuit for record keeping, installation and
               maintenance purposes,

          (c)  An installation technician will be dispatched to the WinStar
               switch, Hub(s) and Lit Building to complete the cross-connects,
               assignments and configure the circuits

          (d)  Lit Buildings shall be connected to Hubs via 38 Ghz radio links.
               Hubs shall be connected to the switch and other hubs using leased
               facilities, radio links or WinStar fiber

          (e)  The circuit will be tested and delivered as a T1facility,
               typically ESF/B8ZS or as otherwise directed by Williams, and
               terminated in the WinStar common space unless otherwise
               contracted in advance by Williams,

          (f)  Williams shall test and approve the circuit according to Exhibit
               A-4

5.       Operations and Routine Maintenance Services.

         Upon approval of the circuit by Williams, WinStar will provide
         monitoring and Routine Maintenance Services (as described below) of the
         circuit in accordance with the Agreement and Schedule B. "Routine
         Maintenance Services" will consist of the following:

5.1.     Support Services.

          (a)  NCC Functions. WinStar shall operate a manned Network Control
               Center ("NCC") twenty-four (24) hours a day, seven (7) days a
               week that monitors the Wireless Fiber Connectivity by means of
               remote surveillance equipment and dispatches maintenance and
               repair personnel to handle and repair problems detected through
               by the NCC or reported to WinStar. WinStar shall provide Williams
               a toll-free telephone number to report problems to the NCC.

          (b)  Site Maintenance. WinStar shall perform appropriate routine
               maintenance on WinStar Equipment, including the DC power plant,
               HVAC equipment, radios and basic building safety equipment
               including alarms and emergency generators in accordance with
               WinStar's then current preventative maintenance procedures.
               WinStar's preventative maintenance procedures shall not
               substantially deviate from industry practice.


<PAGE>

          (c)  Equipment Spares. WinStar shall maintain an inventory of spare
               WinStar Equipment at strategic locations to facilitate timely
               restoration.

5.2.     Planned Network Maintenance Activity

          (a)  WinStar shall avoid performing maintenance between 0600-2200
               local time, Monday through Friday, inclusive, that will have a
               disruptive impact on the continuity or performance level of the
               Williams T-1s. However, the preceding sentence does not apply to
               restoration during emergency situations, restoration of service
               or correction of potential jeopardy conditions.

          (b)  WinStar shall provide Williams with telephone, facsimile, or
               written notice of all non-emergency planned network maintenance
               (a) no later than three working days prior to performing
               maintenance that, in its reasonable opinion, has a substantial
               likelihood of affecting Williams's traffic for up to thirty
               seconds, and (b) no later than ten working days prior to
               performing maintenance that, in its reasonable opinion, has a
               substantial likelihood of affecting Williams's traffic for more
               than thirty seconds. If WinStar's planned activity is canceled or
               delayed, WinStar shall promptly notify Williams and shall comply
               with the provisions of the previous sentence to reschedule any
               delayed activity.

5.3.     Miscellaneous

          (a)  WinStar's maintenance employees shall be available for dispatch
               twenty-four (24) hours a day, seven (7) days a week. WinStar
               shall use commercially reasonable efforts to have its first
               maintenance employee at the site requiring an emergency
               maintenance activity within four (4) hours from the time of alarm
               identification by WinStar's NCC or notification by Williams,
               whichever occurs first. Emergency maintenance is defined as any
               service affecting situations requiring an immediate response.

          (b)  In performing its services hereunder, WinStar shall take
               workmanlike care to prevent impairment to the signal continuity
               and performance of the Williams T-1s. In addition, WinStar shall
               reasonably cooperate with Williams in sharing information and
               analyzing the disturbances regarding the Williams T-1s.

          (c)  WinStar shall, at Williams's request, provide Williams an
               operations escalation list for shall use in reporting and seeking
               redress of exceptions noted in WinStar's performance of Routine
               Maintenance and Non-Routine Maintenance.

<PAGE>
                                                                     Exhibit A-1
                                                          Winstar Target Markets
                            WinStar Networked Cities

         Targeted WinStar Markets.
              As of the Effective Date, WinStar anticipates that the Targeted
              WinStar Markets will be the following (as listed in alphabetical
              order):

1.       Atlanta, GA*                   26.      Minneapolis/St. Paul, MN*
2.       Austin, TX                     27.      Nashville, TN
3.       Baltimore, MD*                 28.      New Orleans, LA
4.       Boston, MA*                    29.      New York City, NY*
5.       Buffalo, NY                    30.      Newark, NJ
6.       Charlotte, NC                  31.      Norfolk, VA
7.       Chicago, IL*                   32.      Oak Brook, IL*
8.       Cincinnati, OH                 33.      Oakland, CA
9.       Cleveland, OH                  34.      Orange County, CA
10.      Columbus, OH*                  35.      Orlando, FL
11.      Dallas, TX*                    36.      Philadelphia, PA*
12.      Denver, CO*                    37.      Phoenix, AZ*
13.      Detroit, MI                    38.      Pittsburgh, PA
14.      Ft. Worth, TX*                 39.      Portland, OR
15.      Greensboro, NC                 40.      Riverside/San Bernardino, CA
16.      Houston, TX*                   41.      Salt Lake City, UT
17.      Indianapolis, IN               42.      San Antonio, TX
18.      Jacksonville, FL               43.      San Diego, CA*
19.      Kansas City, KS*               44.      San Francisco, CA*
20.      Long Island, NY                45.      San Jose, CA
21.      Los Angeles, CA*               46.      Seattle, WA
22.      Louisville, KY                 47.      St. Louis, MO
23.      Memphis, TN                    48.      Stamford, CT
24.      Miami, FL                      49.      Tampa, FL*
25.      Milwaukee, WI                  50.      Washington, DC*




         *  Signifies a city with an operational Hub.

<PAGE>
                                   Exhibit A-2

                             Implementation Schedule

          The following table sets forth the schedule for WinStar's rollout of
          the WinStar Targeted Markets. By each date set forth below, WinStar
          commits to implement one or more Hubs in the indicated number of
          WinStar Target Markets. 

          The cities indicated in the column labeled "WinStar Target Markets"
          are those that WinStar currently plans to implement in the
          corresponding timeframe. They are listed in alphabetical order, not in
          order of implementation. WinStar reserves the right to substitute
          other cities for those indicated (provided that such substitute cities
          shall be of comparable size and within the top one hundred (100)
          metropolitan serving areas (MSAs)), or to change the implementation
          date of any particular city, so long as the Total Implemented cities
          target is reached during the relevant time frame. 

          WinStar will provide Williams with notice of its target date to
          install a Hub in a WinStar Target Market as soon as reasonably
          practicable, but in any event, within five (5) business days following
          the date WinStar obtains the Required Rights for a Hub building in the
          WinStar Target Market. 

          Except as provided in this Exhibit A-2, no other changes may be made
          to this Exhibit A-2 without the mutual written agreement of the
          Parties.


          Date               Total Implemented          WinStar Target Markets
                           WinStar Target Markets
- ------------------------- -------------------------     ----------------------
   At Effective Date                 20                     See Exhibit A-1
- ------------------------- -------------------------    -----------------------
    1999
- ------------------------------------------------------------------------------
        3/31/99                      20
- --------------------------------------------------
        6/30/99                      20                    Cleveland, OH
                                                           Detroit, MI
- --------------------------------------------------         Indianapolis, IN
                                                           Miami, FL
        9/30/99                      23                    Milwaukee, WI
                                                           St. Louis, MO
- --------------------------------------------------         Seattle, WA

        12/31/99                     26
- --------------------------------------------------

<PAGE>



- ---------------------- -------------------------- --------------------------
        Date               Total Implemented          WinStar Target Markets
                        WinStar Target Markets
- ---------------------- -------------------------- --------------------------

    2000
- ----------------------------------------------------------------------------

                                                       New Orleans, LA
       3/31/00                       29                Newark, NJ
- -----------------------------------------------        Oak Brook, IL
                                                       Orange County, CA
       6/30/00                       32                Orlando, FL
- -----------------------------------------------        Oakland, CA
                                                       Pittsburgh, PA
       9/30/00                       35                Portland, OR
- -----------------------------------------------        San Antonio, TX
                                                       San Jose, CA
      12/31/00                       38                Stamford, CT
- ---------------------- -------------------------- ---------------------------

    2001

- -----------------------------------------------------------------------------
                                                       Austin, TX
       3/31/01                       41                Buffalo, NY
                                                       Charlotte, NC
- -----------------------------------------------        Cincinnati, OH
                                                       Greensboro, NC
       6/30/01                       44                Jacksonville, FL
- -----------------------------------------------        Long Island, NY
                                                       Louisville, KY
       9/30/01                       47                Memphis, TN
                                                       Nashville, TN
- -----------------------------------------------        Norfolk, VA
       12/31/01                      50          Riverside/San Bernardino, CA
                                                       Salt Lake City, UT
- ---------------------- ------------------------ ------------------------------



<PAGE>



                        WinStar Hubs Delivered at Closing


- ---------------------------------- ---------------------------
      Target WinStar Market           Number of Hubs Built
- ---------------------------------- ---------------------------
           Atlanta, GA                         3
- ---------------------------------- ---------------------------
          Baltimore, MD                        1
- ---------------------------------- ---------------------------
           Boston, MA                          5
- ---------------------------------- ---------------------------
           Chicago, IL                         4
- ---------------------------------- ---------------------------
          Columbus, OH                         1
- ---------------------------------- ---------------------------
           Dallas, TX                          7
- ---------------------------------- ---------------------------
           Denver, CO                          6
- ---------------------------------- ---------------------------
         Fort Worth, TX                        1
- ---------------------------------- ---------------------------
           Houston, TX                         3
- ---------------------------------- ---------------------------
         Kansas City, MO                       1
- ---------------------------------- ---------------------------
         Los Angeles, CA                       6
- ---------------------------------- ---------------------------
         Minneapolis, MN                       1
- ---------------------------------- ---------------------------
          New York, NY                         5
- ---------------------------------- ---------------------------
          Oak Brook, IL                        1
- ---------------------------------- ---------------------------
        Philadelphia, PA                       3
- ---------------------------------- ---------------------------
           Phoenix, AZ                         1
- ---------------------------------- ---------------------------
          San Diego, CA                        2
- ---------------------------------- ---------------------------
        San Francisco, CA                      3
- ---------------------------------- ---------------------------
       Tampa/St. Pete, FL                      1
- ---------------------------------- ---------------------------
         Washington, DC                        2
- ---------------------------------- ---------------------------


<PAGE>

                                   Exhibit A-3

                             Collocation Provisions

1.1.     License.

          Williams shall have the right to locate, install, maintain and operate
          interconnection equipment at one central office in each WinStar Target
          Market (the "Collocation Site") as designated by mutual agreement of
          the Parties, during the Term. This right shall be used only for
          Williams' interconnection to the Wireless Fiber Services.

1.2.     Real Estate Rights.

          (a)  No use of Collocation Sites required or permitted under this
               Agreement shall create or vest in Williams any easements or other
               ownership or property rights of any nature in WinStar's real or
               personal property. WinStar shall construct and operate such
               space, and Williams shall cause its equipment to be installed and
               operated in accordance with WinStar's policies and
               telecommunications industry standards for similar collocation
               arrangements.

          (b)  Williams shall not make any construction changes or material
               alterations to the interior or exterior portions of the
               Collocation Site, including cabling or power supplies for the
               equipment, without obtaining WinStar's prior written approval.
               WinStar shall have the right to perform and manage any
               construction or material alterations within the Collocation Site
               and related areas at rates to be negotiated between the Parties
               hereto.

1.3.     Equipment and Basic Services.

               (a)  At each Collocation Site, WinStar shall provide separate
                    access (to space not located in its switch or transmission
                    room), space, HVAC, and DC power at Williams' expense (up to
                    fifty (50) amps) for one rack space adequate to contain a
                    rack (measuring 26 inches (width) x 24 inches (depth) x 78
                    or 84 inches (height)). Williams may request additional rack
                    space, which WinStar may provide in its discretion. Williams
                    shall supply its own cabinets.

               (b)  Williams' use of the Collocation Site, installation of the
                    equipment, and type of equipment installed shall at all
                    times be suitable for the central office environment and
                    subject to Williams's adherence to generally accepted
                    industry standards, security rules and reasonable rules of
                    conduct established by WinStar for the Collocation Site.
                    Without limiting the foregoing, Williams acknowledges and
                    agrees that it shall not be permitted to install or
                    otherwise utilize equipment that (i) generates heat greater
                    than 1200 watts per cabinet; or (ii) has a weight load of
                    greater than 100 pounds per square foot. Williams shall not
                    erect any signs or devices to the exterior portion of the
                    Collocation Site without submitting the request to WinStar
                    and obtaining WinStar's written approval, which may be
                    withheld in its sole discretion.


<PAGE>

               (c)  WinStar shall not arbitrarily or discriminatorily require
                    Williams to relocate the equipment; however, upon sixty (60)
                    days' prior written notice or, in the event of an emergency,
                    such time as may be reasonable, WinStar reserves the right
                    to change the location of the Collocation Site. WinStar will
                    work in good faith to minimize any disruption to Williams'
                    services as a result of such relocation. WinStar shall be
                    responsible for the cost of improving the Collocation Site
                    to which the equipment may be relocated, and for relocation
                    of equipment interconnected to WinStar services.

               (d)  Notwithstanding anything to the contrary, WinStar shall in
                    no event be responsible for providing any operations,
                    maintenance, consulting or other related services with
                    respect to any equipment owned, operated, or under the
                    direct or indirect control or supervision of Williams.

1.4.     Facilities.

          WinStar shall support the overall operation of the Collocation Site
          (e.g., HVAC, janitorial services, environmental systems maintenance
          and power plant maintenance) at no additional charge to Williams.
          However, Williams shall be required to maintain the Collocation Site
          in an orderly manner and shall be responsible for the removal of
          trash, packing, cartons, and related items from the Collocation Site.
          Further, Williams shall maintain the Collocation Site in a safe
          condition including not storing combustible materials therein.

1.5.     Access.

          (a)  Williams will have access to the Collocation Site on a seven (7)
               day by twenty-four (24) hour basis, except where Williams'
               equipment is located in WinStar space. Where Williams' equipment
               is in WinStar space, each visit by Williams to the Collocation
               Site will be required to use escort services furnished by WinStar
               from the time Williams's employees sign in upon entering the
               Collocation Site to the time Williams's employees sign out upon
               leaving the Collocation Site. Where Williams' equipment is in
               WinStar space, Williams shall not enter a Collocation Site
               without WinStar escort. Williams will provide reasonable prior
               notice for any such visit. Charges for escort services, if any,
               shall be in accordance with WinStar's then-current standard
               rates, subject to Sections 6.4 and 6.5 of the Agreement.

          (b)  At least fourteen days before beginning any delivery,
               installation, replacement or removal work, Williams must:


<PAGE>

               (i)  Submit a methods, operations and procedures document ("MOP")
                    and a statement of work ("SOW") to WinStar. WinStar will
                    respond to such submission within seven (7) days of receipt.

               (ii) Obtain WinStar's written approval with respect to the SOW,
                    MOP and choice of suppliers and contractors, which approval
                    shall not be unreasonably withheld. 

               WinStar may request additional information before granting
               approval and may require scheduling changes and substitution of
               suppliers and contractors as conditions of its approval. Approval
               by WinStar shall not constitute an endorsement of Williams'
               supplier or contractor. Williams will remain solely responsible
               for the selection of the supplier or contractor and all payments
               for construction work or any other work relating thereto.

          (c)  Williams may not provide, or make available to any third party,
               space within the Collocation Site without WinStar's prior written
               consent, which may be withheld in its sole discretion. If
               Williams breaches this obligation, Williams shall be in breach of
               its license to the Collocation Site and WinStar may immediately
               terminate that license.

1.6.     Renewal.

          Any option granted to Williams to renew its license to occupy the
          Collocation Site shall be contingent on the election by WinStar to
          continue to own or lease the Collocation Site in which the Collocation
          Site is located for the duration of the Renewal Period(s), with such
          election to be exercised at the sole discretion of WinStar.



<PAGE>
                                   Exhibit A-4

                          Standards and Specifications

1.       General

         The documents attached to this Exhibit A-4 represent the standards and
         specifications applicable to the Wireless Fiber Connectivity, as of the
         Effective Date. (Please note that "B Site" is WinStar's internal term
         for a Qualified or Lit Building.) The attached documents, which shall
         be maintained and updated by WinStar from time to time in the ordinary
         course of its business, except as limited by Section 12.17(b) of the
         Agreement, are:

          (a)  Switch Site Environmental Requirements;

          (b)  B Site Build Out Process;

          (c)  Hub Construction Technical Bulletin;

          (d)  Hub Facility Design Criteria;

          (e)  NSO Site and Equipment Test and Acceptance; and

          (f)  DS-1/DS-3 Certification and Acceptance Performance Objectives.

2.       Acceptance and Testing

          2.1. Hub Acceptance Process.

          (a)  WinStar shall perform acceptance testing of the Hubs in a timely
               manner to verify compliance with Acceptance Standards set forth
               in Section 2.2 of this Exhibit A-4. Williams shall have the
               right, but not the obligation, to have personnel present to
               observe the acceptance testing and WinStar shall provide Williams
               prior notice of WinStar's testing schedule. Within thirty (30)
               days after the conclusion of any acceptance testing conducted by
               WinStar on any given Hub, WinStar shall provide a copy of the
               test results to Williams.

          (b)  Williams shall have the right, but not the obligation, at its
               sole expense, to conduct its own acceptance testing to verify
               compliance with Acceptance Standards. If Williams elects to
               conduct its own acceptance testing, it shall notify WinStar of
               its intent to do so (including dates and locations) and shall
               complete such testing within the thirty (30) day review period
               set forth in Section (c) below. WinStar shall have the right, but
               not the obligation, to have personnel present to observe
               Williams' acceptance testing. Within twenty (20) days after the
               conclusion of such testing, Williams shall provide a copy of the
               test results to WinStar. Williams' exercise or non-exercise of
               its right to conduct acceptance testing shall not affect the
               length of the thirty (30) day time periods.


<PAGE>

          (c)  If, within thirty (30) days after receipt by Williams from
               WinStar of the test results referred to in Section (a), above, or
               of the results of re-testing as set forth below, Williams
               reasonably determines that the Hubs do not meet the Acceptance
               Standards, Williams shall, within such thirty (30) day period,
               notify WinStar of such determination and shall identify in
               writing the specific data that indicate such failure to meet the
               Acceptance Standards.

          (d)  Upon receiving notice pursuant to Section (c), above, that some
               portion of the Hubs do not meet the Acceptance Standards, WinStar
               shall either:

               (i)  Expeditiously take such action as reasonably necessary to
                    cause such portion of the Hubs to meet the Acceptance
                    Standards and re-test the Hubs in accordance with the
                    provisions of this Section; or

               (ii) Notify Williams that WinStar disputes Williams'
                    determination that the Hubs do not meet the Acceptance
                    Standards. In such event, the Parties shall agree upon on a
                    mutually acceptable company that shall re-test the Hubs. If
                    that test determines that the Hubs meet the Acceptance
                    Standards, Williams shall pay the testing company's charges
                    and shall be deemed to have accepted the relevant Hub(s).
                    Otherwise, WinStar shall pay the testing company's charges
                    and perform the corrective action and re-testing set forth
                    in Subsection (i).

          (e)  After taking corrective actions and re-testing the Hubs, WinStar
               shall provide Williams with a copy of the new test results and
               Williams shall again have all rights provided in this Article
               with respect to such new test results. The cycle described above
               of testing, taking corrective action and retesting shall take
               place until the Hubs meet the Acceptance Standards.

          (f)  If the acceptance tests show that the Hubs meet the Acceptance
               Standards, and Williams does not object to such tests within the
               time periods specified in Section (c), Williams shall be deemed
               to have accepted the Hubs. Either case shall constitute
               "Acceptance" of the Hubs.

2.2.     Hub Acceptance Standards.

          The Acceptance Standards applicable to Hubs require that:

          (a)  The Hub complies with WinStar's then-current construction
               standards and specifications;

          (b)  All related interior space is completed;

          (c)  Primary and backup power systems are installed and operational;

          (d)  Primary and redundant HVAC systems are installed and operational;

          (e)  Connectivity to the WinStar switch location is installed and
               operational;

          (f)  Antennas are mounted in the designated building space in
               conformance with Required Rights; and

          (g)  Radio alarm and monitoring systems are installed and operational.


<PAGE>
                                     WinStar
                     Switch Site Environmental Requirements


1.       Space

         Switch & Transmission   3600
         Collocation             1000   * = May be placed in 5ESS Growth Areas
         WWI Hub                  800
          * Office Space          550
          * MAP Room              350
                                -------
         Total                   6300 Sq. Ft.

         These are approximate figures and will vary based on each site's
layout.

2.       AC Power

         480V  600 amp approximately
         208V  750 amp approximately

         The switch is powered by -48V DC power derived from 480V or 208V AC
         (depending on building supply) rectified and backed up by gel cell
         batteries. Architect to specify High In-rush Breakers for the
         Rectifiers.

3.       Ceiling Height

         10 Ft. AFF Minimum clear above equipment line-ups.

4.       Floor Loading

         100 lbs. Per Sq. Ft. in equipment area - switch, transmission 
                  & collocate
         200 lbs. Per Sq. Ft. to support batteries (stacked 4 high)
                      770 lbs. per battery
                        4 batteries per stack
                        2 stacks per string
                      ------
                     6160  per string

5.       Floor Tile

         Commercial Grade with Anti-static wax.

6.       Environmental Alarms

         Provide for the following:

               1.   Fire - Heat & Smoke - Pre-action Control Panel

               2.   High temperature - Honeywell Sensor Device

               3.   Low Temperature - Honeywell Sensor Device

               4.   High Humidity - Honeywell Sensor Device

               5.   Low Humidity - Honeywell Sensor Device

               6.   Switch Room Door Alarms - Security System

               7.   Commercial AC Failure - Engine Annunciator Panel

               8.   AC Switch - Gen Transfer - Engine Annunciator Panel


<PAGE>

               9.   Liebert Drip Pan Water Alarm - Remote LIQUI-TEC Annunciator

               10.  Water Alarm - Switch Room - Remote LIQUI-TEC Annunciator

               11.  Water Alarm - Power Room (1A) - Remote LIQUI-TEC Annunciator

               12.  Low Fuel - Storage Tank - Storage Tank

               13.  Low Fuel - Day Tank (1A) Engine Annunciator Panel

               14.  Liebert Failure - Liebert Unit


          Engineering Notes:

               1.   Three Honeywell sensor devices will be ordered and placed in
                    the Power Room, Transmission and Switch areas.

               2.   The Liebert Common Alarm point will be strapped together and
                    reported as one Liebert failure.

               3.   All alarm points wired to a pull box, below the false
                    ceiling, in the vicinity of the CDF (SSLPDF). They should be
                    pigtailed and tagged or terminated on a connecting block.

               4.   The WinStar Switching Engineer will provide for Lucent to
                    cable from the pull box to the CDF for crossconnect to scan
                    points in the 5ESS. Lucent will connect on to the pigtailed
                    lead and stencil the CDF - 89 block as to the alarm type.

               5.   The annunciators should be mounted in the MAP Room . 

               6.   The Architect should specify and install the Honeywell
                    Sensors, Annunciator, the Liebert Alarms, Water Alarm,
                    Engine and Pre-Action Panel, etc.

7.       Lighting

         A 20 ckt. - 20 amp (120V) panel needs to be provided in the equipment
         room (as spotted by Lucent). This panel will be provided for Lucent to
         power their Frame & Aisle lights and convenience receptacles. Frame and
         aisle lights will be provided by Lucent in all line-ups being provided.
         General lighting must be provided elsewhere.

8.       Grounding

         Lucent will provide a C. O. Ground bar and locate per their floor plan.

         From this ground bar, a 750 MCM needs to be run to the principal ground
         point which is a recognized building perimeter ground ring, driven
         ground system, and on the utility side of the water meter. At that
         point, the connection point must be cadwelded and compression fitting
         to the 750 MCM is required. We must be careful when using the utility
         side of the water meter because of the use of PVC. The WinStar Switch
         Engineer will determine the principal ground point.

9.       Telephone Closet

         This requirement will be site specific and will require either a new
         closet built in our equipment room or the re-use of an existing closet.
         Either case, there must be 200 shielded pair, run from their closet to
         the common distributing frame for the building. WinStar will provide
         the connecting blocks in the closet.

         Lucent will provide connection from the closet to inter-connect
         locations within the switch. Room.
<PAGE>

10.      Collocation Room

          This room shall be isolated from WinStar Equipment Room with access
          from a common corridor. A cable hole shall be made for cable rack
          access from WinStar's equipment room to this collocation room. Lucent
          to spot on their cable rack plan.

          This room shall be approximately 1,000 sq. Ft. in size and have two AC
          receptacle circuits run around the perimeter. General lighting to be
          provided. Also provide a 20 circuit 20 amp 208 AC panel located on the
          wall in the Collocation Room.

11.      MAP Room

          This is the maintenance room where interface terminals shall be
          located. Two AC circuits shall be wired into the room for receptacle
          service in the perimeter wall.

          This room shall be approximately 350 sq. Ft. and be provided with
          general lighting.

          Provide a 3' high by 5' long panel with a 1' writing shelf mounted on
          a wall in the MAP room for the purpose of mounting test phones. This
          unit to be mounted 40" AFF.

12.      Emergency Lighting

          The equipment rooms, including the collocation room, shall be equipped
          with emergency re-chargeable battery packs (or equivalent) sufficient
          to light egress path out of equipment room.

13.      Emergency Generator

          A 350 KW generator and a 1,000 gal. Fuel storage tank is required. A
          25-75 gal. Day tank should be provided if required.

          The engine will be equipped with auto start and auto transfer.

14.       AC Requirements

          The AC requirements for a fully built out switch room is approximately
          60 Ton. AC is required on a 24 hour basis and should include
          redundancy. Lucent will provide heat release figures for all cabinets.
          From these figures, the exact requirements can be calculated.

15.      Humidity/Temperature

          The 5ESS-2000 will operate successfully anywhere between 65 and 85
          degrees Fahrenheit and 30% to 80% relative humidity. Performance will
          degrade if the temperature or humidity is allowed to change too
          rapidly; rate of temperature change should be kept below 1 degree in 4
          minutes. Normal (plus or minus 2 degrees and plus or minus 5% RH)
          controls will normally maintain these conditions. The machine will
          continue to operate at temperatures as high as 120 degrees Fahrenheit,
          but this will cause accelerated circuit pack failure for some time
          after the "burn". I recommend the controls be set to maintain a
          constant 76 degrees Fahrenheit year around.


<PAGE>

16.      Filtration

         All air induced into the space (both outside and recirculated) should
         be filtered using a medium efficiency (30% or greater by ASHRAE Dust
         SpotTest) filters. On rare occasions the medium efficiency filter may
         not prevent build-up of particulates on or inside the equipment
         cabinets at an unacceptably high rate. This can be caused by the
         presence of unusually fine particulates or very large amounts of
         average size particulates. In either case the remedy is to use filters
         of a high enough efficiency to give satisfactory performance. Filters
         should be changed at least once every six months (or more often if
         recommended by the manufacturer), or when filters are so "loaded up"
         that the fan system can not maintain proper room pressurization as
         described below.

17.      Room Pressurization

         The room should be pressurized so that the pressure inside the
         equipment space is 0.2 to 0.5 inches of water gauged above the areas
         bordering the equipment spaces with all doors closed. Higher pressures
         are acceptable as long as door operation does not become too difficult
         or dangerous. With the doors open there should be enough positive
         pressure to maintain a continuous flow of air out of the room over the
         entire area of all openings. If this cannot be accomplished then
         appropriate "air curtain" devices or a double door "airlock" should be
         provided to prevent the migration of unfiltered particulates into the
         equipment space. A pressure gauge should be installed in the space with
         probes to both the equipment area and the "outside" area to read the
         pressure difference. The reading on this gauge will only be relevant
         with the room in its "normal (closed) condition. A Dywer model 2000-00
         "Magnehelic" Gauge is suitable for this application.

18.  Ventilation

         "Outside" air induction of five per cent of the circulated air quantity
         is recommended. Successful applications have been designed as low as
         two per cent induction. The quantity induced must only be sufficient to
         maintain acceptable air quality in the space. If there is no noticeable
         "warm equipment" smell outside of the immediate area of the cabinets
         then sufficient induction can be assumed.

19.  Manager Office

         A room of approximately 125 sq. ft. shall be provided for the
         Operations Manager's office. Normal lighting and receptacle to be
         provided. This office may or may not open directly into the equipment
         room. Preferably this office should be within an administration area.

20.  Technician & Administration Space

          There shall also be a space for two cubicle enclosures and a
          receptionist in or around the Manager's Office area.

21.  Break Room/Conference Room

         A room large enough to house 10 people comfortably shall be provided
         close to the proximity of the equipment room, preferably in the
         administration area as previously mentioned.

         If a sales force is collocated with the switch, by strategically
         positioning the conference room, it could be shared by both groups.

<PAGE>

22 Riser Space

          We need to have at least two 4" risers to the roof and two to the
          basement for access.

23.   Freight Elevator

          Must be able to handle at least 3500 lbs. And have a 7' high door and
          the elevator should be 6' W x 8' D x 10' H.

24.  Sprinkler System

         A dry pipe system is required.

25.  Water Pipes

          No building water supply pipes are allowed to be run in the equipment
          room. They must be re-routed.

26.  Window Covering

         If at all possible, windows should be walled off for security reasons.

The above requirements are an attempt to pull together various items that are
relative to the telephone equipment and personnel needs for each site.


Merle Peterson
(Rev. 4-22-97)


<PAGE>
                                   WINSTAR







                                B SITE BUILD OUT

                                     PROCESS

                                   DESCRIPTION
                                        &
                                   PROCEDURES









                                   Prepared by

                                     WinStar

                               Network Deployment
                                Support Services





<PAGE>



PURPOSE

     The purpose of the B Site Build Out Process is to provide an overview and
guidelines of the simultaneous activities involved in the construction of On-Net
B Sites. Prior to the construction phase of this process, there are several
preliminary steps that are crucial to the successful selection, construction and
activation of a B Site. The flow process described in this document is
represented in the following chart, and detailed in a brief description of the
activities and responsibilities for each step. WinStar Program Management will
scheduled intervals of activities that are tracked by the Program Manager of
Implementation for each region.

This document provides a single uniform guideline for install contractors and
vendors to provide price/fee quotes and documented proposals to pre-equip and
install WinStar's On Net B Site Locations. This document is not intended to
replace or be used in lieu of WinStar Engineering requirements or local Building
Code Regulations.


         SCOPE OF WORK


The Scope of Work relating to the installation of WinStar B Site cabinets/racks
will be presented as three separate phases of performance.

Phase One will be the Site Survey of the proposed building utilizing the WinStar
B Site Evaluation form (hereinafter referred to as the "evaluation form"). Phase
Two will be the creation of B Site specific drawings (hereinafter referred to as
the "drawings") depicting installation of the roof top antenna mount
positioning, cable riser path (s), placement of the WinStar   cabinet,
electrical requirements positioning, and location of customer termination
interconnect cable. Phase Three will be the actual installation of the WinStar B
Site cabinet according to the regulations documented in Phases One and Two,
WinStar's Engineering requirements and local Building Code requirements.

Each phase of the process is separate and will be awarded separately.
Additionally, WinStar's acceptance of one phase does not automatically
constitute an award for construction of the subsequent phases. Contractors and
vendors must respond with unit pricing for each phase exclusive of the other.
Price/fee quotes must be submitted within forty-eight (48) hours after the
contractor performs a Phase One B Site Survey and seventy-two (72) hours after
requesting Phase Two site specific drawings.

Phase Three, the physical installation and activation of the B Site Equipment,
is to be initiated by the contractor within forty-eight (48) hours of
notification by the designated WinStar representative. Construction for this
phase must be complete within five (5) working days.

Extenuating circumstances resulting in delays will be addressed on a
case-by-case basis. Payments may be impacted in the event delays are caused
and/or initiated by the contractor/vendor.



<PAGE>



         B SITE BUILD OUT PROCESS


o    Site Acquisition Identifies a selection of buildings in the scheduled city
     
o    NDSS PM (Program Management) coordinates the build out schedule - Internal
     tracking begins

o    A Regional Vendor/Contractor is selected based upon the following criteria:

     The ability to preform preliminary site evaluation and preform a LOS survey
     Provide a detailed Technical Specifications package such as -
     drawings/layouts Installation and Activation

o    The selected regional contractor reviews the potential site.

     The Building Management is presented with a package defining WinStar's
     build out plan and model B site equipment specifications

o    A Site Evaluation Form is completed (Preliminary LOS- RF study) and
     following the guidelines specified in the site evaluation form the
     contractor prepares a Site Specification Package containing
     Drawings/Renderings, Roof Mounts, Room/Equipment Layouts 

o    The contractor provides package to WinStar's PM, COI, and Construction for
     review 

o    Site Acquisition presents the lease with a detailed technical package to
     the Building Management for approval and the appropriate signatures

o    PM coordinates the schedule with the Contractor to pick up the equipment
     from Tier 2 staging area

o    Site Acquisition notifies the PM upon lease completion, PM provides
     Contractor with a Work Authorization form for completion and schedules
     installation

o    Internal process underway, an ISR is generated activating the ASAP process
     and Frequency Planning coordinates path assignments

o    Upon site installation completion, PM schedules a Site Walk Through/ Punch
     list for B Site Test and Acceptance and completes the hand off to
     Operations for Site certification





<PAGE>

B SITE IMPLEMENTATION FLOW PROCESS - PHASE 1

<TABLE>
<S>                 <C>                                   <C>           <C>               <C>                <C>   
Road Runner          Vendor Bid process
finalized            - vendor package sent                               Site Survey                           - Construction
     .               - generic package recvd by             PM schedules                                        - Real Estate
     .                 Construction                         kickoff &    Contractor to                         -COI to review Mech/
     .               - Construction selects                 procedures   perform survey    Site Eval package      Elec drawings
     .             . vendor and notifies PM of ...........  projects    -Site Evaluation ..to flow through.....
     .             . vendor selection                       schedule .. -Drawings created  PM to:             - Provide go/no-go 
  Real Estate      .                                                    -LOS completed                          with/recommendation
visits/reviews site.                                                    -SOW generated                          if required    
     .             .                                                                                          - Review contractor
     .             .                                                                                            costs        .
     .             .   Site Identified/                                                                                      .
     .             ... Preliminarily                                                                                         .
     .             .    Qualified                                                                                            .
     .             .                                                                                                         .
  RF Engineering   .  75% Trigger                                                                                            .
  performs pre- ....  notification from                          GO/NO-GO                                                    .
  freq approval       Real Estate                      .......   DECISION  ...................................................
                                                       .  No             .    Yes          Construction & COI
                                                       .                 . 
                                                       .                 ................. - Finalize SOW (extremes &
                                                       .                 .                   abstracts)
                                                       .                 .                 - Produce checklist
                                                       .                 .                 - Schedule PM w/vendor
                                                       .                 .                 - Approve contractor
                                                       .                 .                 - Generate ISR
                                                       .                 . 
                                            Return to Real Estate to     ................. RF Engineering                    B
                                              identify/re-establish      .                 completes freq plan................
                                                                         . 
                                                                         . ............... Real Estate notified &            A
                                                                         .                 secures lease ....................
                                                                         . 
                                                                         .                 PM notifies COI to
                                                                         ................. load ASAP
</TABLE>


 
<PAGE>
                 B SITE IMPLEMENTATION FLOW PROCESS - PHASE II


<TABLE>
<S>      <C>                 <C>        <C>       <C>                                                  <C> 

          Real Estate                             PM notifies procurement to produce ................... PM to verify
    A     signs lease and                         Letter of Intent to contractor                         equipment
    .....   notifies PM .........................                                                        availability
                                                  - PM coordinates installation with                          .
                                          ......  contractor; produces schedule                               .
                                          B                                                                   .
                                                                                                              .
          Pre-wire site      No            Pre-wire to         PM/Construction to                             .
          and handoff to ................. equip process ..... schedule contractor         Yes             Equipment
               Ops                         in excess of 10       for equipment   ........................  available?
                .                            days?                 retrieval                                   .
                .                                .                         .                                   .
                .                            Yes .                         .                                   .  No
                .                                .                         .                                   .
                .                            Equip site                    .                                   .
       Construction Complete                     .                         .                                  PM notifies
                                                 .                         .                                   Logistics
     - Formal handoff from PM/COI to         Develop                       .                                    .
            Ops completed                    punchlist/                    .                                    .
                 .                           handoff                       .                                  Logistics
                 .                           documentation                 .                                    locates
             PM officially                       .                         .                                  equipment and
             closes project                      .                         .                                   notifies PM
             with Real                           .                         .                                    .
               Estate                            .                         .                                    .
                                       Construction Complete               .                                  PM notifies
                                                                           .                                 Construction
                                     - formal handoff from PM/COI to       .                                 of equipment
                                          Ops completed                    .                                 availability
                                                  .                        ......................................
                                                  .                         
                                             PM officially                  
                                             closes project                 
                                               with Real                    
                                               Estate                      
</TABLE>


<PAGE>



         SITE SURVEY


         Prior to the commencement of any installation, a certified installation
team will conduct a site survey at the designated installation location(s). This
team will be designated by WinStar NC&D and will be comprised of contractors,
WinStar personnel, or a combination of both. The Site Survey Team will comply
with the procedures described below. The Site Survey Team should always work in
cooperation with the building engineer/manager while performing the site survey.
These guidelines generally apply to rooftop installation or towers.

Preparation

The Site Survey Team will be dispatched by WinStar NC&D to the location of the
installation.

WinStar NC&D will provide the Site Survey Team detailed information related to
building access contacts, phone numbers, and the scheduled date of the site
survey. This information will be provided in advance to the Site Survey Team
immediately after initial WinStar contact with building(s) management.

The Scope of Work relating to the B Site Evaluation (hereinafter referred to as
the "evaluation") covers in a general form the following sample of requirements
which equates to a complete building profile. WinStar has determined that the
following factors are effectively significant to the successful installation of
B Site Equipment:

         o     Positioning of the antenna mounts.
         o     Penetration of roof top to gain access to cable risers.
         o     Cable riser capacity/constraints.
         o     Core boring vertical floors in riser pathways (if required).
         o     Identify inside wiring distribution pathways.
         o     Power availability and grounding requirements.
         o     Positioning of the WinStar B Site Cabinet.

All proposed WinStar B Site buildings will be surveyed utilizing the standard
form. The survey process must be initiated by a designated a WinStar
representative. B Site Evaluation Forms will be provided as required and are the
property of WinStar and are not to be utilized for any purpose other than that
requested by WinStar.

The contractor/vendor must respond to WinStar within twenty-four (24) hours upon
receipt of notification to perform.

GPS measurements to include the following:

          o    Longitude and latitude to the nearest second.
          o    Ground elevation within one (1) meter.

Line of Sight to WinStar designated HUB building:

         o      Confirmation of LOS between the two designated buildings.
         o      Physical confirmation by actual site roof top visits.
         o      Notification of potential obstructions or related interference.

The above requirements are a sample of the data required to complete the survey
form. 
Prior to submitting a bid response the attached documents must be reviewed
for additional requirements.

Site Survey Team Procedures

Confirm a clear, unobstructed Line of Sight (LOS) between Building A and
Building Z. (Building A pertains to the predetermined Hub Site and Building B
pertains to the B Site). In the event the LOS is obstructed by new construction,
trees, or roof top mechanical installations, immediately notify WinStar NC&D to
describe the environment and discuss possible remedies. Pay special attention to
window washing gear. Determine if it will block LOS during use.


<PAGE>

If LOS does not exist or if distance is too great, look for several potential
repeater buildings/towers. Obtain building management information and phone
numbers. If access to these buildings cannot be obtained for on-site survey,
consult with WinStar Program Management for assistance.

Obtain the latitude and longitude of the A and Z sites with a GPS receiver and
record the data on the WinStar Site Evaluation Form.

Roof Mount Location and Type:

Determine the best location for placement of the antenna mount that ensures
optimum LOS between Building A and Building Z and provides ease of installation
for the Installation Team.

Determine the type of antenna mount:

The type of antenna mount required is determined by the roof top construction
and any obstructions located on the roof (e.g., mechanical housings).

If an existing tower or antenna framework is present on either Building A or
Building Z, the Site Survey Team will immediately advise WinStar NC&D of the
potential to use these structures for installation, as well as the name and
telephone number of the organization responsible for the structure.

Identify and/or confirm the location(s) of the Indoor Unit (IDU), rack/cabinet
placement.

Grounds:

Electrical grounds are required for the proper operation and protection of
transceivers as well as protection of personnel and other equipment connected to
the radios. Improper ground procedures put the equipment and its environment at
risk.

ODU ground:

Grounds should be used on the ODU to the mast or tower. For a rooftop
installation, the mast should be grounded to building steel. Long cable runs for
grounding purposes should be avoided.

IDU ground:

If the IDU is connected to a floating battery power source, such as a Central
Office environment, generally no further precautions must be taken. However,
when using a WinStar power supply or other power supply or other AC rectifier
without benefit of battery back-up, special care must be taken to prevent the
formation of AC ground loops, which can cause a variety of problems. Ideally,
the source for reference ground for the outside and inside units will be the
same and will be building steel. Bonding the ground to building steel to the
inside unit is very important. Often, however, the inside and outside units are
far apart, which creates ground loops. Every effort both to find and to
eliminate these loops should be made before certifying installation.

Ground Loops:

Ground loops are formed when two or more points on the radio system are
referenced to different grounds. They also occur when the distance from the
outside unit and the inside unit is increased, thereby increasing the chance for
a difference in potential between the two reference points. After going through
all Installation steps, a test for the existence of ground loops should be made.
With the equipment turned on and the cable disconnected from the IDU, measure AC
voltage between the chassis of the inside unit and the braid on the coaxial
cable. This reading should be in millivolt range. (Note: local codes may be
stricter than this.) If it exceeds this reading, a possibility for ground loops
exists and must be eliminated. The second test to be performed is to measure the
DC voltage between the chassis and the braid on the cable. This reading should
not exceed 5 VDC. If the reading is in excess of 5 VDC, steps must be taken to
eliminate the ground loop. There are several ways to eliminate ground loops.
Bonding the two points in the system with a low resistance cable is one way to
resolve this problem. However, if this is not feasible, the AC ground must be
broken at the outside unit. AC grounds can occur at the outside unit due to
installation of receptacles on the tower, other equipment mounted on the tower,
or tower lighting. If the first ground used is referenced to the mast or tower
itself, it must be removed and referenced to another, better ground. Again
building steel is preferable. Check the second ground point where the cable
enters the building, if this does not solve the problem. Re-connect it directly
to building steel or to the reference point for the lightning arrestor field.


<PAGE>

Use 8 AWG cable or better for this purpose. The ideal situation, especially for
a building with multiple installations, is to create a ground buss in the common
space in the building and run very heavy gauge (MCM 50 or better) to the buss
and connect all grounds to the buss via copper lug connections. Determine the
cable path for the cable(s) between the ODU and the IDU. This requires
inspection of the roof top for a portal conduit that allows entry from the roof
top to the internal cable riser pathway. If a portal conduit is not available,
or the existing ports are filled, notify WinStar Operations and provide a
recommended solution. While on the premises, obtain the name and telephone
number of the roofing contractor used by, or recommended by, the building
manager. This information will assist in expediting the installation of a portal
conduit.

Measure the distance of the proposed cable path between the ODU and the IDU and
add 10%. This additional cable will be used for the creation of service loops
associated with the installation. The maximum length of the coax cable is 800
feet if using plenum rated and 1000 feet if using non-plenum. Determine the
source and connection points of the building roof top ground. Proper grounding
of the antenna mounting serves as lightning protection and reduces the
possibility of electrical shock to personnel and equipment damage. Do not use
building lightning protection or aluminum to ground. Use building ground (i.e.,
I-Beam, stairwell, etc.). 

Determine the source and connection points of building/earth ground in the
immediate area of the IDU installation. When possible, perform steps 1-11
simultaneously in Buildings A and Z.

Document the Site Survey results on the WinStar Evaluation Form and fax the
completed form to WinStar Program Management at 703-790-4672. Retain a copy of
the completed site survey form for reference during the actual installation.


         SITE SPECIFIC - TECHNICAL DRAWINGS

         Phase Two is the creation of B Site specific drawings that are in
direct association with the technical and physical requirements of a successful
B Site installation as it relates to the existing/proposed B Site building.

         The drawings must accurately represent the physical environmental
structure of the B site building as well as the actual addition of 100% of the
components of the WinStar B Site equipment package. Drawings are to be computer
software-enhanced with one (1) inch to equal no less than twenty-four (24)
actual feet of the structure, whether it constitutes roof top, vertical risers
or floor space.

         Roof top drawings are to display the position of the WinStar antenna
mount in relationship to adjacent roof top structures as currently located and
are to be accurate in relationship to Polar designations. Cable penetration
locations are to be specifically designated as to entry point by Polar location
on the roof top and an accurate measurement from a fixed permanent
position/structure on the roof top.

         Cable path risers are to be accurately designated as to specific
vertical runs in relationship to interior locations by room and shaft
designators, floors to be transgressed, roof top paths, and break-out locations.
These designations must be specific as to point of roof penetration to the point
of termination at the WinStar B site equipment location.

         The proposed core boring of new cable riser space is to be specific as
to locations by room and shaft designators, floors to be transgressed and degree
of anticipated difficulty in successful competition. Core boring proposals on
the site specific drawings are to include the actual locations of existing cable
runs/conduits in relationship to the proposed new core bore holes.

         Positioning of the WinStar B Site cabinet is to be accurately depicted
on computer software enhanced drawings to reference the exact location within
the B Site Building environment. Detail should be shown to reference room
designator number, floor designator and exact floor space to be occupied with
detailed references to existing devices in the immediate space.


<PAGE>

         Contractors are encouraged to enhance the level of visual detail within
the environment to include electrical outlet references, grounding positions, AC
power distributors, point of entry for the WinStar coax cable and pathway within
the facility.

         In addition, drawings of the B-Site equipment location are to designate
the specific customer interface wiring positions when available. Wiring
backboards and termination blocks are to be identified by exact wall mounting
locations within the environment.

         In the event that electrical outlets are unavailable and new outlets
are required, the drawings are to reflect the exact proposed positioning of the
required outlets in exact relationship to the WinStar B Site cabinet location.
Measurements are to be recorded and listed in exact distance between the
outlet(s) and the WinStar B Site cabinet.

         The contractor must make available to WinStar computer enhanced site
specific drawings within seventy-two (72) hours of formal notification by a
designated WinStar representative. Under no circumstances are B Site specific
drawings to be delivered or presented to other parties outside the WinStar
organization without prior written consent from an authorized WinStar
representative.




<PAGE>



         SITE EVALUATION FORM




        [FORM FOR SPECIFYING DATE RELEVANT TO SITE LOCATION PROCESS]


<PAGE>


B SITE PRE-EQUIP GUIDELINES

         DESIGN

             The WinStar microwave radio system is a compact, cost effective,
highly reliable, easy to configure microwave radio system. The WinStar microwave
radio system is also referred to as a LINK, consisting of two separate terminals
operating in the same frequency band on complementing transmit and receive
frequencies.

             Each WinStar microwave radio system consist of an antenna and
mount, outdoor unit (ODU ), indoor unit ( IDU ) and IDU to ODU interconnect
cable. The IDU of each terminal is connected to the Customer's termination
equipment via an approved WinStar interconnect cable.

             The WinStar microwave radio system is designed for ease of
installation and operation. The outdoor unit ( ODU ) is designed to either be
mounted directly to the antenna on an antenna mount assembly or depending on the
model be mounted remotely from the antenna.

             The indoor unit ( IDU ) is designed to be mounted in a standard 19-
inch EIA relay rack or in an enclosed lockable cabinet in a designated secure
location. Prior the installation of a WinStar microwave radio system, the
proposed install site must be site surveyed and documented as required by
WinStar. The Site Survey is one phase of several that will allow the successful
installation of a WinStar Microwave radio system to proceed.

             On-Net facilities are connected to Hubs via 38 GHZ circuits in a
point-to-point configuration. On-Net facilities provide customer access via high
speed and low speed circuits in a point-to-point design. WinStar field personnel
will follow the pre-construction design criteria d in this document to prepare
for the installation of On-Net facilities.


         NETWORK ARCHITECTURE

              On-Net sites are customer access points for microwave links that
  transmit traffic to and from Hubs. Hub and On-Net sites communicate via
  multiple DS3/DS1 radio links in the 38 Ghz portion of the spectrum. The Hubs
  function as concentrators for these microwave links, providing DS3 or DS1
  service for buildings within the Hub service area. In some instances , the
  traffic from these buildings will be bundled into multiple DS3 links over a
  fiber SONET Ring backbone, or connected by low frequency radio shots. This
  fiber backbone will initially be provided by a competitive access provider
  (CAP).

              In simple terms, the network architecture features On-Net sites as
  customer access points for traffic, with Hubs transmitting and receiving
  traffic from On-Net sites via microwave links. Hubs concentrate that traffic
  from On-Nets and transmit (or receive) traffic over fiber links to any one of
  the following:

          o        WTI 5ESS switch sites

          o        Other Hubs

          o        IXCs (inter-exchange carriers)

          o        LECs (local exchange carriers)

          o        CAPs (competitive access providers)






<PAGE>



         B-SITE PRE-EQUIP CONSTRUCTION GUIDELINES


This section provides a single, uniform guideline for field personnel that
outlines the scope of work required for pre-equipping of On-Net sites (B-sites).
These guidelines can be used for obtaining price quotes from service vendors.
Any questions should be directed to Network Construction & Deployment. If the
cost for meeting the guidelines below exceeds $5,000 consult with NC&D
Construction Engineering.

Complete the WinStar B Site Evaluation Form and submit with price quote.

             Scope of Work

     o    Assemble and install antenna mount/s in a position that ensures
          line-of-site (LOS) to Hub facility

     o    Install plenum rated cable between common equipment location and
          penetration point

     o    Install five (5) RG 8 cables from mount to common equipment location,
          ensure all cables are tagged with WinStar provided cable
          Identification tags 

    o     WinStar's policy does not dictate the use of conduit between common
          equipment and point of penetration.

     o    Install five (5) WinStar provided surge protectors at the building
          interior point of penetration (refer to diagram 0-7)

     o    Install water proof sleeves at cable point of penetration

     o    Protect cable in rigid conduit or cable trough if crossing open roof
          area

     o    Common equipment location to be based on cost of proximity to building
          MDF

     o    Identify inside wiring distribution pathways

     o    Core drill verticals if required and sleeve

     o    Grounding mount per local practice. Refer to WinStar Antenna mount
          grounding requirements

     o    Utilize open bay configurations for secure areas

     o    Utilize lockable cabinet configurations for non protected areas


Install RG-8 plenum coax cables from the roof mount to equipment location.
Install at least 5 cables in all cases. Install an additional two cables if the
two cables can be installed for less than $2000. Otherwise, obtain price quotes
for the additional two cables and submit to NC&D. The maximum allowable IDU to
ODU cable length is 1000 feet. Ensure any exposed cable on rooftop is protected
(by conduit, wire tray, or PVC), from the antenna mount to building penetration
point. Install lightning arrestor and surge protection inside building near
point of penetration. B-sites do not require that conduit be used between
equipment location and roof penetration point, only that the cable be sleeved at
penetration points. Local codes or building management requirements may require
otherwise. Exceptions should be explained and justified in writing to Network
Engineering. Verify internal distribution path for inside wiring through
existing telco risers. Maximum allowable STP cable length is 550 feet. Establish
cable paths sufficient for vertical distribution as identified by the Site
Survey and insert removable fire protection as required. 

Pre wiring of riser cable is not recommended, inside wiring will be installed on
a ICB basis depending on customer requirements.

Determine the cable path for the cable(s) between the ODU and the IDU. This
requires inspection of the roof top for a portal conduit that allows entry from
the roof top to the internal cable riser pathway. If a portal conduit is not
available, or the existing ports are filled, notify WinStar Operations and
provide a recommended solution. While on the premises, obtain the name and
telephone number of the roofing contractor used by, or recommended by, the
building manager. This information will assist in expediting the installation of
a portal conduit.

<PAGE>

Measure the distance of the proposed cable path between the ODU and the IDU and
add 10%. This additional cable will be used for the creation of service loops
associated with the installation. The maximum length of the coax cable is 800
feet if using plenum rated and 1000 feet if using non-plenum.



         B SITE POWER REQUIREMENTS


WinStar utilizes the Reltec/Lorain MZ-60 rectifier as the standard power supply
for B sites. This -48VDC power system is capable of supplying between 10 and 60
amps of DC current. The system can accept various AC feeds depending on site
requirements. Use the following guidelines when ordering initial AC power.

It is the recommendation of WinStar Engineering to equip the rectifier at 240VAC
@ 50 amps. This would allow full utilization of the power plant.

Determine B site rectifier, AC power requirements. This should be done during
the preliminarily site evaluation phase. Install one (1) 120 or 240 VAC, 20-50
amp single phase circuit per MZ-60 power plant. The circuit will terminate into
a NEMA L5-20-50 Twistlock female connector and be mounted in an electrical
outlet box. The male connector will be supplied on a pre-manufactured power cord
for the rectifier assembly. This circuit will be used for the Rectifier
Assembly.

Smaller sites with limited growth potential may install two (2) AC circuits of
110 VAC @ 20 amps. Factors such as separate metering requirements and cost
factors need to be considered when selecting AC power.

1.   Install one (1) 120 VAC, 20 amp single-phase circuit. The circuit will
     terminate into a NEMA L5-20 Twistlock female connector, mounted in an
     electrical outlet box. This circuit will be used for the AC outlet strip,
     which will host the cabinet fan assembly power requirement. It may also
     supply power to future equipment, test equipment, and PCs used for
     maintaining the network.

2.   The male connector for the cord of the AC outlet strip must be changed to a
     NEMA L5-20 Twistlock Male Connector. This connector will be assembled
     during the equipment reconfiguration.

3.   Provision one (1) 20 amp circuit for every three cabinets installed at a
     site. The AC outlet strips may be connected in series, in-between cabinets.

4.   Install the outlet boxes no lower than 84 inches from the base of the floor
     and not to exceed more than 8 feet from the cabinet location.





<PAGE>





         B SITE POWER CONSUMPTION

         The Building Management at B sites may be concerned about the power
consumption of the WinStar equipment installed on their premises. By using Chart
N, it is possible to evaluate the amount of AC power that will be used by
various equipment configurations.

         To use the chart it is first necessary to calculate the DC requirement
of the WinStar equipment - this will typically be 1.5 amps for each IDU/ODU and
0.6 amps for each Mux. Using this figure, the monthly AC power consumption can
be found from the chart. The chart uses figures taken from the Lorain MZ10F50
Technical Document and assumes a 730 hour month.


EQUIPPED B SITE GUIDELINES

         This phase of the B Site process will define the criteria for a fully
equipped B Site Installation.


         EQUIPMENT


                  STANDARD B SITE EQUIPMENT ORDERING FORMS

Central Office Implementation updates the master equipment ordering forms and
provides approved copies to construction and logistics to standardize equipment
ordering.



The following is an approved B Site equipment ordering form.

Current Electronic Copies are available from Logistics and Central Office
Implementation

<PAGE>



          Standard Configuration 1 Build  P-COM 8xT1 Link
<TABLE>
<CAPTION>

Power                                              PART#                       MFG            QTY
- -----------------------------------------------------------------------------------------------------
<S>       <C>                                      <C>                        <C>            <C>
          Rectifier, 10 Amp                        486524401                   Reltec         2
- -----------------------------------------------------------------------------------------------------
          Fan Module, Rectifier                    427215600                   Reltec         2
- -----------------------------------------------------------------------------------------------------
          Mounting Cabinet, Rectifier              588242000                   Reltec         1
- -----------------------------------------------------------------------------------------------------
          Battery, 12V  100 Amp                                                Sure Power     4
- -----------------------------------------------------------------------------------------------------
          Shelf, Battery                           412805200                   Reltec         1
- -----------------------------------------------------------------------------------------------------
          Power Strip                              IBAR-12                     Tripplite      1
- -----------------------------------------------------------------------------------------------------
          Fuse Panel, Alarm  19"-23"               009-0002-1005               Telect         1
- -----------------------------------------------------------------------------------------------------
Mounts
- -----------------------------------------------------------------------------------------------------
          Mounts:  (one of following)                                                         1
- -----------------------------------------------------------------------------------------------------
               Non-Penetrating Roof                PSH-4                       Baird
- -----------------------------------------------------------------------------------------------------
               Wall  60"                           91148                       Microflect
- -----------------------------------------------------------------------------------------------------
               Wall  100"                          91147                       Microflect
- -----------------------------------------------------------------------------------------------------
               Tripod, Penetrating                                             Microflect
- -----------------------------------------------------------------------------------------------------
Cable                                                                                         Feet
- -----------------------------------------------------------------------------------------------------
          RG-8 Plenum (feet)                       C-0216                                     5K
- -----------------------------------------------------------------------------------------------------
          Octopus, 10'                             5006-10                                    2
- -----------------------------------------------------------------------------------------------------
          IDU External Alarms                      5016-08                                    1
- -----------------------------------------------------------------------------------------------------
          16 awg 2 pair (feet)                     9080-RED/BLK                               20ft
- -----------------------------------------------------------------------------------------------------
          DC Pwr 6 awg Red (feet)                  0601-THHN-RED                              10
- -----------------------------------------------------------------------------------------------------
          DC Pwr 6 awg Blk (feet)                  0601-THHN-BLK                              10
- -----------------------------------------------------------------------------------------------------
          Fuse Panel Alarm (feet)                  9501                                       20
- -----------------------------------------------------------------------------------------------------
          Rectifier Alarm (feet)                                                              20
- -----------------------------------------------------------------------------------------------------
          Mux Alarm (feet)                                                                    20
- -----------------------------------------------------------------------------------------------------
           25 pr STP cable 24awg                   CMP-025-24-SSP ANIX                        100
- -----------------------------------------------------------------------------------------------------

- -----------------------------------------------------------------------------------------------------
Cabinets
- -----------------------------------------------------------------------------------------------------
          Indoor Enclosure                         GL 8401/32                  Great Lakes    1
- -----------------------------------------------------------------------------------------------------
Radio Equipment
- -----------------------------------------------------------------------------------------------------
          IDU, 8x                                  16488                       PCom           1
- -----------------------------------------------------------------------------------------------------
          ODU (one of following)
- -----------------------------------------------------------------------------------------------------
               Band 1                              16268                       PCom
- ------------------------------------------------------------------------------------------------------
               Band 2                              16260                       PCom
- -----------------------------------------------------------------------------------------------------
               Band 3                              16266                       PCom
- -----------------------------------------------------------------------------------------------------
               Band 4                              16258                       PCom
- -----------------------------------------------------------------------------------------------------
          Antenna, 12"                             23770-002                   Andrews        1
- -----------------------------------------------------------------------------------------------------
</TABLE>

<PAGE>

<TABLE>
<CAPTION>

Power                                              PART#                       MFG            QTY
- -----------------------------------------------------------------------------------------------------
<S>       <C>                                      <C>                        <C>            <C>
DSX
- -----------------------------------------------------------------------------------------------------
          DSX-1 Panel, Jack Field                  MINI DSX-1/W                ADC            1
- -----------------------------------------------------------------------------------------------------
          DSX-1 Module                             MINI DSX-1/WM               ADC            1
- -----------------------------------------------------------------------------------------------------
          Mounting Panel, DSX-3 3 Position         010-0000-0701               Telect         1
- -----------------------------------------------------------------------------------------------------
          Chassis, DSX-3/4  16 Position            1000000301                  Telect         1
- -----------------------------------------------------------------------------------------------------
          Module, DSX-3/4                          1090010401                  Telect         1
- -----------------------------------------------------------------------------------------------------
Local Termination Field
- -----------------------------------------------------------------------------------------------------
          Split 50 pair block                      6639-01-001-01              Krone          4
- -----------------------------------------------------------------------------------------------------
          Stand off bracket                        S89D                        Siemons        4
- -----------------------------------------------------------------------------------------------------
          Wire management rings                                                               4
- -----------------------------------------------------------------------------------------------------
          19" wall/cabinet mount                                               Krone
- -----------------------------------------------------------------------------------------------------
Miscellaneous
- -----------------------------------------------------------------------------------------------------
          Connector, RG-8 Plenum                   NS 5848-5                                  20
- -----------------------------------------------------------------------------------------------------
          Cable Standoff                           10001-01                                   20
- -----------------------------------------------------------------------------------------------------
          Lightning Protection Device              RT-N/W                                     5
- -----------------------------------------------------------------------------------------------------
          Ground Bar                               40280013                                   1
- -----------------------------------------------------------------------------------------------------
          Mounting Bar, 19"                        76017                                      1
- -----------------------------------------------------------------------------------------------------
          Cable Ties, 4" Blk                       TYT-T18R-0-M                               bulk
- -----------------------------------------------------------------------------------------------------
          Cable Ties, 8" Blk                       TYT-T30M-0-M                               bulk
- -----------------------------------------------------------------------------------------------------
          Screws                                                                              2
- -----------------------------------------------------------------------------------------------------
          Nut, Star Locking (6/32)                                                            2
- -----------------------------------------------------------------------------------------------------
          Terminal, 12 Position                    N70149                      BEAU           1
</TABLE>


<PAGE>
          Standard Configuration 1 Build  P-COM DS-3 Link

<TABLE>
<CAPTION>

Power                                           PART#                       MFG            QTY
- -------------------------------------------------------------------------------------------------
<S>       <C>                                  <C>                        <C>            <C>
- ------------------------------------------------------------------------------------------
           Rectifier, 10 Amp                    486524401             Reltec        2
- ------------------------------------------------------------------------------------------
           Fan Module, Rectifier                427215600             Reltec        2
- ------------------------------------------------------------------------------------------
           Mounting Cabinet, Rectifier          588242000             Reltec        1
- ------------------------------------------------------------------------------------------
           Battery, 12V  100 Amp                                      Sure Power    4
- ------------------------------------------------------------------------------------------
           Shelf, Battery                       412805200             Reltec        1
- ------------------------------------------------------------------------------------------
           Power Strip                          IBAR-12               Tripplite     1
- ------------------------------------------------------------------------------------------
           Fuse Panel, Alarm  19"-23"           009-0002-1005         Telect        1
- ------------------------------------------------------------------------------------------
Mounts
- ------------------------------------------------------------------------------------------
           Mounts:  (one of following)                                              1
- ------------------------------------------------------------------------------------------
                Non-Penetrating Roof            PSH-4                 Baird
- ------------------------------------------------------------------------------------------
                Wall  60"                       91148                 Microflect
- ------------------------------------------------------------------------------------------
                Wall  100"                      91147                 Microflect
- ------------------------------------------------------------------------------------------
                Tripod, Penetrating                                   Microflect
- ------------------------------------------------------------------------------------------
Cable                                                                               Feet
- ------------------------------------------------------------------------------------------
           RG-8 Plenum (feet)                   C-0216                              5K
- ------------------------------------------------------------------------------------------
           Octopus, 10'                         5006-10                             2
- ------------------------------------------------------------------------------------------
           IDU External Alarms                  5016-08                             1
- ------------------------------------------------------------------------------------------
           16 awg 2 pair (feet)                 9080-RED/BLK                        20ft
- ------------------------------------------------------------------------------------------
           DC Pwr 6 awg Red (feet)              0601-THHN-RED                       10
- ------------------------------------------------------------------------------------------
           DC Pwr 6 awg Blk (feet)              0601-THHN-BLK                       10
- ------------------------------------------------------------------------------------------
           Fuse Panel Alarm (feet)              9501                                20
- ------------------------------------------------------------------------------------------
           Rectifier Alarm (feet)                                                   20
- ------------------------------------------------------------------------------------------
           Mux Alarm (feet)                                                         20
- ------------------------------------------------------------------------------------------
            25 pr STP cable 24awg                                                   100
- ------------------------------------------------------------------------------------------
Muxes
- ------------------------------------------------------------------------------------------
           Mux, M13 NEC                         RC-28D                NEC
- ------------------------------------------------------------------------------------------
Cabinets
- ------------------------------------------------------------------------------------------
           Indoor Enclosure                     GL 8401/32            Great Lakes   1
- ------------------------------------------------------------------------------------------
Radio Equipment
- ------------------------------------------------------------------------------------------
           IDU, 8x                              16488                 PCom          1
- ------------------------------------------------------------------------------------------
           ODU (one of following)
- ------------------------------------------------------------------------------------------
                Band 1                          16268                 PCom
- ------------------------------------------------------------------------------------------
                Band 2                          16260                 PCom
- ------------------------------------------------------------------------------------------
                Band 3                          16266                 PCom
- ------------------------------------------------------------------------------------------
                Band 4                          16258                 PCom
- ------------------------------------------------------------------------------------------
           Antenna, 12"                         23770-002             Andrews       1
- ------------------------------------------------------------------------------------------
</TABLE>


<PAGE>


<TABLE>
<CAPTION>

Power                                           PART#                 MFG           QTY
- ------------------------------------------------------------------------------------------
<S>       <C>                                  <C>                    <C>            <C>
DSX
- ------------------------------------------------------------------------------------------
           DSX-1 Panel, Jack Field              MINI DSX-1/W          ADC           1
- ------------------------------------------------------------------------------------------
           DSX-1 Module                         MINI DSX-1/WM         ADC           1
- ------------------------------------------------------------------------------------------
           Mounting Panel, DSX-3 3 Position     010-0000-0701         Telect        1
- ------------------------------------------------------------------------------------------
           Chassis, DSX-3/4  16 Position        1000000301            Telect        1
- ------------------------------------------------------------------------------------------
           Module, DSX-3/4                      1090010401            Telect        1
- ------------------------------------------------------------------------------------------
Local Termination Field
- ------------------------------------------------------------------------------------------
           Split 50 pair block                  6639-01-001-01        Krone         4
- ------------------------------------------------------------------------------------------
           Stand off bracket                    S89D                  Siemons       4
- ------------------------------------------------------------------------------------------
           Wire management rings                                                    4
- ------------------------------------------------------------------------------------------
           19" wall/cabinet mount                                     Krone
- ------------------------------------------------------------------------------------------
Miscellaneous
- ------------------------------------------------------------------------------------------
           Connector, RG-8 Plenum               NS 5848-5                           bulk
- ------------------------------------------------------------------------------------------
           Cable Standoff                       10001-01                            20
- ------------------------------------------------------------------------------------------
           Lightning Protection Device          RT-N/W                              bulk
- ------------------------------------------------------------------------------------------
           Ground Bar                           40280013                            1
- ------------------------------------------------------------------------------------------
           Mounting Bar, 19"                    76017                               1
- ------------------------------------------------------------------------------------------
           Cable Ties, 4" Blk                   TYT-T18R-0-M                        bulk
- ------------------------------------------------------------------------------------------
           Cable Ties, 8" Blk                   TYT-T30M-0-M                        bulk
- ------------------------------------------------------------------------------------------
           Screws                                                                   2
- ------------------------------------------------------------------------------------------
           Nut, Star Locking (6/32)                                                 2
- ------------------------------------------------------------------------------------------
           Terminal, 12 Position                NH 70149              BEAU          1
</TABLE>


On-Net (B-site) equipment shall be pre-assembled and tested prior to deployment
in the field.


         STANDARDIZED B-SITE EQUIPMENT CONFIGURATIONS

          o    DS1-1 8XT1 IDU 
          o    DS1-2 8XT1 IDU WIRING
          o    DS1-3 8XT1 IDU ALARM WIRING
          o    DS3-1 8XT1 IDU
          o    DS3-2 8XT1 IDU WIRING
          o    DS3-3 8XT1 IDU ALARM WIRING
          o    B-SITE ANTENNA SURGE PROTECTION

         LOCAL TERMINATION FIELD AND CIRCUIT DEMARC

      (See Appendix for Attachments Local Termination Field and WTI Demarc)

          o    Terminate/Extend B site DSX-1 field per the following guidelines
          o    Locate Krone 66 style termination block field per site
               requirements
          o    Field may be located in various locations, including:
                  - wall mounted near common equipment 
                  - rack mounted in either 9 or 23 inch cabinet
                  - mounted in closest telco closet, blocks may be added to 
                    existing 66 type backboards - in telco closets 


<PAGE>

          o    Terminate two (2) 25 pair ABAM cables from DSX-1 panel to first
               row of split 50 blocks
          o    Separate transmit and receive pairs on opposite sides of split 50
               block in upper right position per drawing 

          o    Extend customer cables from local termination field to customer
               premise o Install cross connects from first row of termination
               field (network side) to customer cable termination points
               (customer side)

     Install WTI cross connects from network side blocks to RJ 48X blocks
located on the right side of termination field

<PAGE>



          Appendix - Technical Drawings



                [CHART DIAGRAMMING SITE IMPLEMENTATION TIMELINE]




<PAGE>

Network Construction Engineering
Technical Bulletin No. 550-30-1001-004

This bulletin contains additions or revisions to the WinStar Network
Construction and Development Standard Operating Practices, Volume 1, Revision 1,
(Part No. ###-##-####.)
Insert the following new or changes pages or drawings where indicated.

To:               All Winstar Construction Personnel

From:             Richard Bailey
                  Network Construction Engineer

Re:               Specifications  / Requirements  / Overview
                  Standardized WinStar Hub Construction Models
                  Standardized WinStar Equipment Configurations


Hub Construction Model  # 1
1000 Square foot Hub Facility

Specifications  / Requirements

Designed to accommodate fifty (50) remote customer "B" sites 
Large equipment growth potential / Collocate space available 
Original foot print of 24 equipment bays, expandable 
VAC requirement 400 amps @ 240 VAC or 200 amps @ 480 VAC 
VDC requirement 4-600 amps@ -48VDC @ 8hrs reserve 
Environmentally controlled facility

Hub Construction Model  # 2
500 Square foot Hub Facility


Specifications  / Requirements

Designed to accommodate fifty (50) remote customer "B" sites 
Limited equipment growth potential / Collocate space available 
Original foot print of 24 equipment bays 
AC site power requirements 2-300 amps  @ 240 VAC or 1-200 amps @ 480VAC 
VDC requirement 400 amps @ -48VDC @ 8hrs reserve 
Environmentally controlled facility



<PAGE>


Hub Construction Model  # 3
Less than 200 Square foot Hub Facility


Specifications  / Requirements

Designed to accommodate 25 plus remote customer "B" sites 
No equipment growth potential 
No less then 12 equipment bays 
AC site power requirements 100 amps @240 VAC


Hub Construction Model  # 4
100 Square foot Hub Facility
Equipped with a 4 x14 DMC Equipment Configuration

Specifications  / Requirements

Designed to accommodate up to fourteen remote B sites 
Designed under current B site lease language restrictions 
Utilizes B site power requirements 240vac @ 40a plus 110vac @ 20a
Utilizes all DMC radio equipment ( requires B sites to be configured with DMC
IUD's) 
All active equipment SNMP compliant 
Accepts various connectivity schemes
Accepts up to four (4) Low Frequency protected links (or) 
Accepts up to 14 carrier provided DS 3 circuits (or) 
Designed to support carrier provided Optical Mux (OC XX ) with DS3 terminations
8xT1 or DS3 outbound links depending on available back bone bandwidth
     Utilizes Great Lakes 8401 model 23 inch cabinets 
     Initial equipment complement is pre-assembled for quick turn up time
Requires 100 square foot leased space, sufficient to accommodate four
28"Wx28"Dx84"H lockable cabinets with front and rear access.




<PAGE>


Standardized Equipment Configurations
Equipment elevation and assembly drawings available in NC&D Construction Manual

Hub (WinStar Node )
4 x14 DMC Equipment Configuration (see hub construction model 4)

12x T1 P-Com IDU configuration 
12x DS3 P-Com IDU configuration 
12x CAC/NEC Mux bay 
Antenna Bay configuration 
12x M 1/3 Mux Bay configuration 
DSX-1 Cross connect bay configuration 
DSX-3 Cross connect bay configuration 
Local Termination Field Hub



"B" (Customer Site )

P-Com 8xT1 x 5 IDU configuration 
P-Com DS3 x 2 m1/3 configuration 
DLC add on configuration 
DLC stand alone configuration 
Local Termination Field Customer site


<PAGE>
1.       HUB FACILITY DESIGN CRITERIA

1.1.     INTRODUCTION

          The material presented in this section relates to the space planning
          and design, the construction, and the communication equipment
          installation for the WinStar Hub Facilities.

     1.1.1.   SPACE PLANNING AND DESIGN

          There are two categories of Hub facilities: 500 - 1000 square feet,
          200 - 500 square feet. The space planning size of the facility is
          determined by the number of antennas the facility plans to support,
          although, due to lease arrangements, the gross hub size may differ
          from the Hub equipment's physical space needs. Unless otherwise
          designated in the following guidelines, the Hub design aspects
          associated with finishes, power, and environmental support equipment
          is similar for all three type of hubs.

          The architectural and engineering (A/E) firm is responsible for
          producing the construction drawings and specifications necessary to
          construct the Hub. The design of all facility components shall be in
          accordance with all local, state, regional and/or national building
          codes which have jurisdiction at the site location. The construction
          engineer shall be responsible for reviewing these governing building
          codes and assuring that the Hub is built according to the drawings and
          specifications.

          The typical hub facility space planning process revolves about the
          support of telecommunications equipment located within the Hub space,
          and the transmission/reception (antenna) equipment located exterior to
          the space. WinStar engineering holds the responsibility for relating
          Hub telecommunication equipment quantities and antenna locations to
          the A/E at the onset of the space planning process. Lease information
          associated with tenant construction standards/guidelines is to be made
          available to the A/E, along with any other landlord requirements such
          a those associated with review and approval of construction documents.

          The A/E holds the responsibility for obtaining, with the assistance of
          the WinStar Engineer as necessary, any base building plans of
          documents needed for Hub design, or must otherwise develop building
          backgrounds and design documents by audit.

          At the onset of the space planning process, the A/E shall develop
          basic Hub background drawings showing walls, columns, doors, windows,
          floor elevation changes, etc. The A/E shall then initiate a proposed
          Hub equipment layout for WinStar Network Construction Engineering
          approval. The layout shall reflect the items noted on the initial
          WinStar Hub equipment listing noted above, along with "generic" hub
          equipment support systems such as HVAC equipment, electrical
          panelboards, fire alarm panels, etc. Once WinStar Network Construction
          Engineering approval is secured, construction documentation
          preparation can commence.

     1.1.2.   ARCHITECTURAL

          Every site may be unique and each region of the country may have
          special considerations. The following items shall be considered during
          the design:

          1.1.2.1.    Demolition

               Coordinate demolition plan for the leased space. Drawings shall
               indicate removal and legal disposal of items except those
               indicated to be reinstalled, salvaged, or to remain the owner's
               property. Measures shall be taken to prevent damage and soiling
               of the construction during selective demolition. When permitted,
               items may be removed to a suitable, protected storage location
               during demolition and then cleaned and reinstalled in their
               original locations. The contractor shall be required to
               photograph the existing conditions of adjoining construction and
               site access pathways prior to the start of construction, as a
               record of pre-existing conditions, in order to avoid undue
               landlord claims for reparations as a result of construction
               activities. A walk-through of the site with the landlord
               representative, along with walk through notes are to supplement
               the photographs.


<PAGE>

               The construction documents shall be in compliance with EPA
               requirements on hazardous materials before starting demolition.
               Comply with hauling and disposal regulations of authorities
               having jurisdiction.

          1.1.2.2.   Ceiling, Walls & Floor

               Ceilings: Where possible, an open ceiling environment should be
               employed. Should finished ceilings be required due to site
               conditions, the standard minimum acceptable ceiling height for
               the hubs shall be (ten) feet. Should a particular site not
               support the ten floor height, the equipment layout A/E shall
               boldly identify the standard variance on the conceptual equipment
               layout noted above. When planning ceiling heights, consider
               stacked cabinet heights as well as individual cabinet heights. Be
               sure to consider seismic bracing and how it will be implemented
               in the design. Cable tray shall be installed a minimum of six
               inches above equipment, with a minimum of 12 inches clear above
               the tray.

               For standardization purposes, the preferred drop ceiling system
               shall be Armstrong Minaboard Fire Guard 24"x24"x5/8" Cortega
               #842.

               Walls: All walls shall have a minimum of 2.5" sound attenuation
               and 5/8" gypsum board with 3 5/8" metal studs. Walls shall be
               designed for a two hour fire rating. Finish walls and paint
               eggshell white below 8'-0", flat black above 8'-0". Seal all
               penetrations in and out of the space with 3M putty, firestop
               bags, or equivalent. Wall base shall be finished with Johnsonite
               4"x1/8" black vinyl base or approve equal.

               Mounting Boards: The A/E shall specify the installation of two
               (2) 4'x8'x3/4" fire retardant treated plywood boards to be
               located as directed by WinStar. Boards are to be primed and
               painted to match adjacent surfaces.

               Doors: Hub entrance doors shall be 3'-6" x 7'-0"x 1 3/4" hollow
               metal with 1 1/2 hour UL listing and complimentary UL listed
               metal door frame. Door hardware shall be Simplex L-1000
               mechanical cypher locks. Where possible, embed magnetic door
               contacts in door frame for security needs (see below). Door shall
               receive WinStar supplied, contractor installed door decal (or
               other signage) for space identification.

               Floors: Ensure the space has a level floor. Bare concrete floor
               shall be sealed to prevent the generation of dust, dirt, and
               other airborne particles. Standard Hub floor finishes shall be
               Armstrong Imperial #51911 Classic White. Anti-static strip mats
               shall be used in equipment rows.

               All finish material schedules and specifications should be
               included in the design.

               A/E shall indicate on the design documents the designated floor
               space for one (1) storage cabinet, one (1) storage shelving unit,
               and one (1) desk with chair, all to be supplied by WinStar,
               delivered and placed by contractor.

               To be included in the Hub design are the following items:




<PAGE>

               Eye Wash Station: Lab Safety Supply #RC-2121-S (fend-all) 6
               gallon gravity feed eyesaline eye wash station with #RC-2121S-2
               dust cover.



               Full Coverage Face Shield with wall hook: Lab Safety Supply #
               RC-10253 Head/Face Shield or equal.



               First Aid Kit: Lab Safety Supply #RC-10430 Small industrial first
               aid kit for up to 25 personnel



               Fire Extinguishers: One (1) 10 pound carbon dioxide class B and C
                                   One (1) 5 pound dry chemical class A, B & C

          1.1.3. STRUCTURAL

          Standard commercial property will, in most cases, provide adequate
          floor loading capacity for the communications equipment in the typical
          layout scheme. However, stacking and/or back to back placement of
          equipment may exceed the structural capacity of the floor.

          Analysis: Typically, the battery load and power equipment load will
          exceed the structural load limit. A structural analysis shall be
          completed on the entire hub area at the onset of the space planning
          process, and prior to the conceptual equipment layout being sent to
          WinStar for approval. Depending upon the proposed antenna mounting
          structure, a structural study of the antenna location should be
          completed at this time as well. The analysis must include
          consideration for the seismic zone of the facility. The results of the
          analysis shall be transmitted to the WinStar Engineer at the earliest
          possible moment. The following items shall be considered during the
          analysis:

          o        Communication equipment specifications and layout
          o        DC Power Bay specifications and layout
          o        Battery plant specifications and layout
          o        Antenna specifications and layout
          o        Deck hanging loads (mechanical, electrical, plumbing,
                   cable ladder, DC cables, communication cables, etc.)

          Design: Should structural alteration be required as a result of the
          analysis, the construction documents shall reflect all equipment
          layouts with anticipated structural loading characteristics. Included
          on the documents shall be equipment and antenna mounting details
          including seismic restraint connections where applicable.

          1.1.4.   ELECTRICAL

               1.1.4.1.    AC Power Systems

               The purpose of this section is to establish minimum engineering
               parameters to be observed during the design and or retrofit of
               WinStar Wireless, Inc. Hub Facilities AC Power Systems. All
               design articles must adhere to the requirements of National
               Electrical Code, and all applicable state and local ordinances.

               Facility AC Power Systems consist of (3) primary components;
               generation, distribution, and protection systems. All of these
               components are to be engineered to insure maximum cohesiveness
               and operating performance. Successful operation of the AC Power
               System is crucial in insuring the uninterrupted operation of
               WinStar Wireless, Inc. network telecommunications equipment.


<PAGE>

               1.1.4.2.   System Engineering Criteria

               Engineers must observe the following parameters when designing
               WinStar Wireless, Inc. Hub Facility AC Power Systems. Deviations
               from stated parameters must be requested and approved by WinStar
               Wireless, Inc. Network Engineering Group, prior to
               implementation.

               1.1.4.3.   Utility Service

               WinStar Wireless Inc. Hub Facilities shall preferably be equipped
               with (1) 480 Volt 3 Phase 3 Wire Alternating Current Electrical
               Service in order to minimize primary service installation costs.
               Should 480 Volt service not be available, 208 Volt 3 Phase 3 Wire
               service shall be used and treated as the Primary Electrical
               Service. Origination of this circuit can be derived via direct
               interconnection to Local Utility Provider electrical distribution
               grid, or via Subfeed connection to an existing electrical
               service. The electrical service must be engineered to satisfy
               demand loads of network Hub Facility telecommunications, and
               infrastructure support equipment. Service must be equipped with
               facilities to allow for disconnect from utility/existing
               electrical service and a means for metering of electrical energy
               consumption.

               1.1.4.4.  Main Distribution Switchboard

               Should the service be 480 volt, the Hub shall be equipped with
               one (1) 480 Volt 3 Phase 3 Wire Alternating Current distribution
               panel. The panel shall be equipped with Main Disconnect providing
               Ground and Overcurrent Fault Protection for the Service Entrance
               (see Shunt-trip Primary Service Circuit Breaker below). The panel
               shall be engineered for correct voltage, phase, frequency, short
               circuit and continuous current ratings. The panel is to be
               equipped with Branch Circuit Distribution Devices; quantities,
               ratings, and types will be determined by Infrastructure Support
               equipment requirements. Engineering must include execution of
               Fault Current analysis, and Short Circuit Coordination study. The
               panel must also provide limiting devices as required to eliminate
               transient voltage conditions such as spikes and surges which may
               be delivered via Service Entrance or emergency power supply (see
               surge protection information below).

               1.1.4.5.   Emergency Service

               WinStar Wireless Inc. Hub Facilities shall be equipped with an
               Emergency Service Entrance which matches the Hub's Primary
               Electrical Service. This Service Entrance shall be derived via
               installation of a Bulk Distribution Circuit routed from
               Street-Side Portable Generator connection device to one (1)
               Manual Transfer Switch. The street-side connection device shall
               be a lockable fused switch equipped with main lugs for portable
               generator connection. This service shall be utilized via Manual
               Actuation in the event of a sustained Utility Electrical Outage.
               Emergency service must be engineered to satisfy demand loads of
               network Hub Facility telecommunications, and infrastructure
               support equipment. Engineering must provide for execution of
               Fault Current analysis and Short Circuit Coordination studies.
               Manual Transfer Switch shall be ASCO Model 486 with labels
               clearly marking source of both emergency and normal feed.


<PAGE>

               Step-down Transformer

               In the sites with 480 Volt primary service, the secondary
               distribution is to be obtained via the installation of one (1)
               Dry Type, step-down Isolation Transformer. Transformer Primary is
               to be routed from current limiting device contained within the
               main distribution panel board. Transformer Secondary is to be
               routed to Input of Facility Secondary Panel board. Transformer
               and Primary/Secondary circuits are to be engineered to satisfy
               load requirements of Hub Facility telecommunications and
               infrastructure support systems.

               1.1.4.6.  Secondary Distribution

               WinStar Wireless, Inc. Hub Facilities shall be equipped with (1)
               120/208 Volt 3 Phase 3 Wire Alternating Current Secondary Service
               (Primary Electrical Service and Secondary Electrical Distribution
               are considered one and the same where 208 volt service is the
               Primary Electrical service). The panel shall be equipped with
               Main Disconnect providing Ground and Overcurrent Fault Protection
               for the Secondary distribution panel board (see Shunt-trip
               Primary Service Circuit Breaker below). The panel shall be
               engineered for correct voltage, phase, frequency, short circuit
               and continuous current ratings. The panel is to be equipped with
               Branch Circuit Distribution Devices; quantities, ratings, and
               types will be determined by Infrastructure Support equipment
               requirements. Engineering must include execution of Fault Current
               analysis, and Short Circuit Coordination study. For Hub sites
               with incoming service at 208 volts, the secondary distribution
               panel must provide limiting devices as required to eliminate
               transient voltage conditions such as spikes and surges which may
               be delivered via Service Entrance or emergency power supply (see
               surge protection information below).

               1.1.4.7. Shunt-trip Primary Service Circuit Breaker

               The primary Hub electrical service shall be equipped with a main
               disconnect circuit breaker with a shunt-trip device for emergency
               power shutdown. The shunt trip device shall be located after the
               manual transfer switch and before Hub distribution, with the
               possible exception of an independent circuit feeding the fire
               alarm control panel and/or other life safety devices. Emergency
               Power Off switch shall be ASCO model 1243 with labels "TO
               DISCONNECT ELECTRICAL SERVICE".

               1.1.4.8.   Overcurrent Protective Devices

               WinStar Wireless, Inc. Hub Facilities Electrical Distribution
               System is to be engineered with Overcurrent Protective Devices
               that comply with the following parameters:

               Molded Case Circuit Breakers - Sized as required to support loads
               with RMS Symmetrical Interrupting Ratings to match symmetrical
               interrupting ratings coordinated with fault current analysis and
               short circuit study. Breakers are to include permanent Thermal,
               Fault, and Instantaneous Trips per pole. Provide 2-pole 25A
               breakers for current and future rectifiers in accordance with
               equipment schedule.

               Fuses - Sized as required to support loads with UL Class RK-1
               Time-Delay ranges.


<PAGE>

                    1.1.4.9.   Conductors

                    WinStar Wireless, Inc. Hub Facility AC Power System
                    conductor requirements must conform to the following
                    parameters: All conductors are to be AWG type THHN insulated
                    copper only. All conductor termination's are to be performed
                    utilizing Compression (15) Ton High-Press, Hex or
                    Circumventual Crimps will only be accepted. All
                    termination's are to utilize (2) Hole NEMA Spaced Long
                    Barrel Lugs only. All fastening hardware to be #316 Grade
                    Stainless Steel only. All termination's are to be insulated
                    utilizing Thick Wall Heat Shrink. All conductors are to be
                    permanently identified utilizing Fiber Cable Tags only.

                    1.1.4.10. Lighting

                    Adequate lighting is required for a safe and efficient work
                    environment. The design should be energy efficient with low
                    heat generation. UL approved fluorescent light fixtures
                    shall be installed to provide adequate illumination levels
                    throughout the hub. Energy efficient 32W T8 tubes and
                    electronic ballast's should be used to provide 50% decrease
                    in energy usage and a 90% reduction in heat generated by the
                    lights.

                    Emergency backup lighting units should be installed. They
                    should be activated upon loss of AC power. All emergency
                    lights should be UL approved and meet all NEC, OSHA, NFPA,
                    and Life Safety Code requirements.

                    Telephone

                    Each Hub space shall be provided with at least one telephone
                    with high volume ringer.

                    1.1.4.11. DC Power System

                    The purpose of this section is to establish minimum
                    engineering parameters to be observed during the design and
                    or retrofit of WinStar Wireless, Inc. Hub Facilities DC
                    Power Systems. Facility DC Power Systems consist of (3)
                    primary components; rectifiers, batteries, and distribution
                    systems. All of these components are to be engineered to
                    insure maximum cohesiveness and operating performance.
                    Successful operation of DC Power Systems is crucial in
                    insuring the uninterrupted operation of network
                    telecommunications equipment in the event of a utility power
                    outage. As a result of network dependencies DC power systems
                    are designed with redundant capabilities in all primary
                    system components, including rectifiers, divergent
                    distribution paths, and finite stationary battery reserves.

                    1.1.4.12. System Engineering Criteria

                    Engineers must observe the following parameters when
                    designing Hub Facility DC Power Systems. Deviations from
                    stated parameters must be requested and approved by WinStar
                    Wireless, Inc. Network Engineering Group prior to
                    implementation.

                    1.1.4.13. Battery Reserve

                    WinStar Wireless Inc. Hub Facilities shall be equipped with
                    Valve Regulated Lead-Acid recombination batteries to provide
                    power in the event of a utility power outage. Battery
                    reserves shall be engineered to provided adequate capacity
                    required to support Hub Facility DC power demand loads for a
                    finite period of time. Network Hub Facilities must be
                    equipped with a minimum of (8) Hours Reserve capacity.


<PAGE>

                    1.1.4.14. Reserve Calculation

                    Battery reserve capacities must not fall below stated
                    minimum requirements. Modifications to facility network
                    equipment DC demand loads will require re-calculation of
                    battery reserve capacities. Reserve capacity of battery is
                    to be calculated using battery end voltage equaling 1.75
                    volts per cell, and 80% of published (8) Hour Amp Hour
                    Rating. Reserve capacity is to be calculated utilizing the
                    following formula:


                     AH
                     ------  x  C  =  R
                      L

                    AH - Amp Hours

                    L - Demand Load Ampacities

                    C - Correction Factor/0.950

                    R - Reserve Capacity

                    1.1.4.15. Battery Recharge

                    WinStar Wireless Inc. Hub Facilities shall be equipped with
                    Switchmode technology modular rectifiers as required to
                    insure capability of exercising Valve Regulated Lead-Acid
                    recombination station batteries from discharged to full
                    recharge condition within (24) Hours. Rectifier bank must
                    included required capacities and (1) redundant unit.

                    1.1.4.16. Recharge Calculation

                    Recharge capacities must not fall below stated minimum
                    requirements. Modifications to facility network equipment DC
                    demand loads will require re-calculation of battery recharge
                    capacities. Rectifiers are not to be operated beyond maximum
                    current limit of 110% of rated capacity. Recharge capacity
                    is to be calculated utilizing the following formula:

                    1.1 x AH
                    -------------    +   L   =  RC
                        R

                    AH - Amp Hours

                    L - Demand Load Ampacities

                    R - Recharge Capacity/Hours

                    RC - Recharge Current

                    1.1.4.17. System Voltage

                    WinStar Wireless, Inc. Hub Facility DC Power Systems are to
                    be designed to operate within the following voltage ranges:


<PAGE>

                    End Voltage - 42.0 VDC

                    Float Voltage - 54.0 VDC

                    Equalize Voltage - 56.0 VDC

                    High Voltage Shutdown - 57.0 VDC

                    1.1.4.18. Voltage Drop

                    WinStar Wireless, Inc. Hub Facilities DC Power Systems are
                    to be engineered to finite voltage drop levels insuring
                    continued network equipment operation while providing for
                    resistance levels encountered due to transport distances.
                    Voltage drop is to be limited to a maximum of 2.0 VDC
                    throughout linear routing of distribution circuit.

                    1.1.4.19. Voltage Drop Calculation

                    Voltage drop levels are not to exceed stated maximum
                    allowances. Voltage drop is to be calculated utilizing
                    battery end voltage equaling 1.75 volts per cell. Voltage
                    drop is to be calculated utilizing the following
                    calculations:

                    L   x   LL   x   C
                    --------------------    =  CM
                          VD

                    L - Demand Load Ampacities

                    LL - Loop Length

                    C - Constant Factor (11.1)

                    VD - Voltage Drop

                    CM - Circular Mills

                    1.1.4.20. Distribution

                    WinStar Wireless Inc. Hub Facilities DC Power Systems design
                    is to provide for the installation of (1) Main Power
                    Distribution Board and Bulk Distribution Circuit
                    installation to Relay Rack mounted GMT Branch Circuit Fuse
                    Panels. This distribution system is to provide for Hub
                    Facility network equipment DC demand loads as well as
                    equipment interconnection requirements. Main Power
                    Distribution Board is to be designed with a Charge Section
                    capable of accommodating termination of all battery and
                    rectifier sources. Main Power Distribution Board must
                    provide for divergent Bulk Distribution Conductor routing to
                    allow for derived A/B distribution systems from board to all
                    ancillary equipment. Main Power Distribution Board must
                    provide Over-Current Protection for all Bulk Distribution
                    Circuits to insure protection of the entire DC Power System.
                    Electrical fault protection shall be designed to insure
                    correct device coordination, rating, and placement, allowing
                    for circuit interruption closest to fault occurrence.


<PAGE>

                    1.1.4.21. Environment

                    WinStar Wireless, Inc. Hub Facility DC Power Systems are to
                    be engineered to operate without performance degradation
                    within the following controlled environmental levels:

                    Temperature - 32 through 122 Degrees Fahrenheit, Ambient

                    Humidity - 12% through 97% Relative

                    1.1.4.22. System Component Engineering Criteria

                    Section purpose is to establish minimum performance
                    specifications for all components utilized in Hub Facility
                    DC Power System design. All equipment must meet or exceed
                    stated requirements prior to installation consideration.

                    1.1.4.23. Rectifiers

                    WinStar Wireless, Inc. Hub Facility DC Power System utilizes
                    Switchmode rectifier technology. Rectifiers are to be of
                    modular design to accommodate installation within Facility
                    Main Power Distribution Board. All rectifier modules must be
                    capable of Load Sharing with entire plant charge section.
                    Rectifiers are to be listed by Underwriters Laboratories.
                    Rectifiers are to be installed with capacities sufficient to
                    satisfy DC load demands as well as provide for redundant
                    modular unit application. This configuration will allow for
                    the removal of (1) unit from service without effecting
                    station load. Please see Appendix E for rectifiers currently
                    being purchased.

                    1.1.4.24. Batteries

                    WinStar Wireless, Inc. Hub Facility DC Power System utilizes
                    Valve Regulated Lead-Acid recombination battery technology
                    to provide mission critical power to network equipment in
                    the event of a utility power outage. Batteries are to be
                    designed to accommodate the facility DC load demand with the
                    capability to support this demand for a minimum of (8)
                    hours. Load is to be calculated utilizing end voltage
                    equaling 1.75 VPC. Batteries must be capable of being rack
                    mounted to allow for integration within facility technical
                    areas. Racks must satisfy all seismic zone requirements.
                    Disconnecting means must be supplied to allow for isolation
                    of battery from Facility Distribution System. Each battery
                    cell must be individually valve regulated to vent excess
                    pressure. Rated capacity of cell shall be expressed in
                    Ampere Hours based on an (8) hour discharge rate. The abrupt
                    transient response of the cell must not fall below 1.89VPC.
                    Recombination efficiency of the cell must be 95% or greater.
                    Provide Specific Gravity of 1.250. Please see Appendix E for
                    the battery plant currently being purchased.

                    1.1.4.25. Distribution (MPB)

                    WinStar Wireless Inc. Hub Facilities DC Power Systems design
                    is to provide for the installation of (1) Main Power
                    Distribution Board. This Main Power Distribution Board is to
                    provide for Hub Facility network equipment DC demand loads
                    as well as equipment interconnection requirements. Main
                    Power Distribution Board is to be designed with a Charge
                    Section capable of accommodating termination of all battery
                    and rectifier sources. Main Power Distribution Board must
                    provide for divergent Bulk Distribution Conductor routing to
                    allow for derived A/B distribution systems from board to all
                    ancillary equipment. Main Power Distribution Board must
                    provide Over-Current Protection for all Bulk Distribution
                    Circuits to insure protection of the entire DC Power System.
                    Electrical fault protection shall be designed to insure
                    correct device coordination, rating, and placement, allowing
                    for circuit interruption closest to fault occurrence. Board
                    must provide metering, alarms, and control interfaces that
                    are equipped for extension to remote surveillance stations.
                    Board must include provisions for the installation of
                    Battery Disconnecting device, Rectifier module installation,
                    and battery installation. Please see Appendix C for Main
                    Power Distribution Board currently being purchased. For ease
                    in securing DC contractor pricing, the distance between the
                    main ground bar, the batteries, and the main
                    distribution/rectifier bay shall not exceed 20 feet.


<PAGE>

                    1.1.4.26. Distribution (GMT)

                    WinStar Wireless, Inc. Hub Facility DC Power System design
                    is to provide for diversified Bulk Distribution Circuit
                    routing from Main Power Distribution Board to Relay Rack
                    mounted GMT Fuse Panels. These Fuse Panels are to provide
                    A/B Branch Circuit Distribution from panels to network
                    equipment.

                    1.1.4.27. Grounding

                    WinStar Wireless, Inc. Hub Facility DC Power System design
                    must include connection of Main Power Distribution Board
                    Positive Discharge Buss Detail to Facility Master Ground
                    Buss Detail. Grounding cable shall be run in independent "J"
                    hooks supported under cable racks.

                    1.1.4.28. Conductors

                    WinStar Wireless, Inc. Hub Facility DC Power System
                    conductor requirements must conform to the following
                    parameters: All conductors are to be AWG type THHN insulated
                    copper only. All conductor termination's are to be performed
                    utilizing Compression (15) Ton High-Press, Hex or
                    Circumventual Crimps will only be accepted. All
                    termination's are to utilize (2) Hole NEMA Spaced Long
                    Barrel Lugs only. All fastening hardware to be #316 Grade
                    Stainless Steel only. All termination's are to be insulated
                    utilizing Thick Wall Heat Shrink. All conductors are to
                    secured utilizing #9 Round Wax Lacing Cord only. All
                    conductors are to be permanently identified utilizing Fiber
                    Cable Tags only. All conductors are to be routed complete
                    point to point. Use of Splices is prohibited. Cabling from
                    main distribution board to equipment racks shall be
                    supported below cable ladder using "J" hooks.

                    1.1.4.29. Buss

                    WinStar Wireless, Inc. Hub Facility DC Power System design
                    shall provide for all Buss Details to be copper rated on
                    (1000) Amperes per (1) Square Inch of cross-sectional area.
                    Buss details are to be machined and pre-punched.



<PAGE>

          1.1.5.   MECHANICAL

                    In most facilities the existing leased space base building
                    Heating, Ventilation, and Air Conditioning (HVAC) system
                    will not meet the seven days a week 24 hour requirement the
                    WinStar hub demands. To achieve the required cooling and
                    ventilation a dedicated HVAC system will need to be
                    installed. WinStar is currently purchasing several different
                    type of HVAC systems from Liebert Corporation depending on
                    the size and specific requirements of the hub. The location
                    of the hub versus the location of the cooling system heat
                    rejection components ( i.e. air cooled condensers, dry
                    coolers, or exterior wall mounted unitary systems) will
                    determine which type of HVAC system is used for the hub. See
                    Appendix B for types of system being purchased by WinStar
                    for Hub facilities. 

                    The HUB interior design criteria for the HVAC system is
                    based upon the Hub equipment listing provided by WinStar at
                    the onset of the design. The maximum bay of equipment is
                    2700 BTU/hr with a maximum of 130BTU/hr/SF for total
                    facility load. The overall HVAC system must be designed
                    along proper engineering practices, taking into
                    consideration exterior temperature and humidity conditions,
                    sun exposure, and low initial internal head gain due to
                    partial equipment installation. 

                    The following items shall be considered during the design:

                    o    Facility temperature shall be maintained between 66
                         degrees Fahrenheit and 77 degrees Fahrenheit

                    o    Facility relative humidity shall be maintained between
                         30% and 55%

                    o    Noise level 40dBA or below 

                    o    Outside air be kept below 5%

                    o    Redundancy within the system, with one HVAC unit
                         available at all times

                    o    Overhead hung units supported from the deck/structural
                         steel above or exterior wall mounted units outside the
                         hub space

                    o    Drip pan with liquid detector 

                    o    Remote temperature and humidification controls

                    o    Automatic HAVC switch over controls

                    o    Condensate pump where necessary 

                    o    Alarm and shutdown contacts

                    o    Maintenance accessible

                    o    Final testing and balancing


                    1.1.5.1. Thermostats 

                    Thermostats shall be mounted in the vacinity of the air
                    return inlets and should be installed in such a way to
                    minimize unauthorized tampering with the temperature setting
                    controls. A lock box cover on a conventional thermostat may
                    be required if unauthorized temperature resetting is
                    anticipated.


<PAGE>

                    Normal Set-Points and Sensitivities:

                    Temperature:

                    75 degrees F DB     +2 degrees F DB
                                        -

                    Relative Humidity (RH):

                    Minimum RH:      35%, +5%
                                          -
   
                    Maximum RH: 50%, +5%
                                     - 

                    1.1.5.2. Alarms

                    All sites should be equipped with high and low temperature
                    alarms. These alarms should be interfaced with the site
                    security system and monitored around the clock. The sensors
                    must be accurate enough to detect minimal temperature
                    variations.

                    Alarm Set-Points:

                    Temperature:

                                    Low Set-Point:   60 degrees F DB

                                    High Set-Point:  80 degrees F DB

                    Relative Humidity (RH):

                                    Low Set-Point:            30% RH

                                    High Set-Point:           60% RH

                    1.1.5.3. Exhaust Fan

                    For every hub an exhaust fan should be installed. This
                    provides a method of removing excessive heat buildup if the
                    air conditioning units are disabled. The exhaust fan will
                    also remove any gas or vapors that maybe emitted from the
                    batteries. It should be located as high as possible in the
                    hub to remove the maximum amount of heat from the site. The
                    exhaust fan should run continuously to provide at least four
                    air exchangers or 2 CFM/SF. The fan should be interlocked
                    with the fire suppression system.

                    1.1.5.4. Room Pressurization

                    The Hub shall be at a positive air pressure. This room shall
                    be at a positive air pressure relative to all other adjacent
                    spaces and the outdoors. The purpose of maintaining
                    pressurization is to minimize the infiltration of airborne
                    particles.

                    1.1.5.5. Construction Documents

                    The construction drawings and specifications for each hub
                    shall include a listing of all equipment to be installed,
                    noting whether it is to be purchased by WinStar or by the
                    contractor. If purchased by WinStar, equipment submittal
                    sheets and installation instructions shall be included
                    within the construction document package. Arrangements for
                    manufacturer representative start-up and instruction shall
                    be a part of the contractor's work scope for all major
                    equipment items, weather purchased by WinStar or the
                    contractor. The mechanical contractor shall be responsible
                    for all control wiring, including providing a normally
                    closed or normally open circuit for HVAC unit fire alarm
                    shut-down where necessary.


          1.1.6.   FIRE DETECTION AND SUPPRESSION

          The fire detection system shall be a cross-zoned smoke detection
          system linked to a fire alarm control panel (sub-system to the
          building fire alarm control system). The fire suppression protection
          systems for a Hub shall either be a pre-action system if water is
          available in the building, or a FM-200 gaseous system.

          The design of the fire detection and suppression system shall comply
          with the requirements of the State Building Codes, applicable NFPA
          Sections and requirements of the insurance carrier for the project.

               1.1.6.1. Pre-Action System

               The design shall be a complete hydraulically designed pre-action
               sprinkler system which complies with NFPA 13, 24, 26, 70, 72,
               72E, and 72G, ANSI, ASTM, AWS, and MSS.

               The safest type of pre-action system for communication equipment
               is a Double-Interlocked System. This type of system requires the
               activation of both detection system and a sprinkler head before


<PAGE>

               allowing water to flow into the sprinkler system piping. This
               will protect against accidental discharge of water. The A/E
               design should provide for a deluge valve, check valve with rubber
               seat, main water supply control valve with tamper switch, alarm
               pressure switch, air pressure supervisory switch and all trim
               valve gages and components all located within the hub. The deluge
               valve should be electronically operated. The sprinkler system
               shall be supervised with a air compressor and air maintenance
               device.

               Include a pre-action releasing panel for operation of the
               pre-action system. The control unit shall be UL Listed per
               Standard 864 for pre-action and the solenoid shall be listed for
               use with the panel. The control panel shall have the capacity for
               at least two initiative device circuits and inputs from flow, low
               air and tamper switches. The control panel shall also have the
               capacity for two output circuits for trouble and supervisory
               signals to building fire alarm system. The alarm notification to
               the building shall be from the alarm pressure switch. All
               initiating circuits from the panel shall be Style D. The panel
               shall have backup battery and charger for continuous operation of
               system for 24 hours.

               The pre-action system shall include a detection and control
               system for solenoid valve operation on the preaction valve. The
               detection circuits shall be obtained from the release panel.
               Valves controlling sprinklers or water supplies shall be listed
               OS&Y gate valves or butterfly valves suitable for the service
               indicated. Where butterfly valves are used, they shall be lug
               type flanged or grooved so that piping can be disconnected on one
               side of the valve and the valve still hold pressure. All valves
               shall be provided with listed tamper switches with both normally
               open and normally closed contacts.

               1.1.6.2. Installation

               Before commencing installation, the Fire Protection Contractor
               shall prepare a complete set of Working Drawings required for the
               approval and the installation of the fire protection system.
               Spacing of the sprinklers shall be coordinated with lights, cable
               tray system, air conditioning duct, and architectural reflected
               ceiling plan (if any) prior to the installation. The Fire
               Sprinkler Contractor shall submit working plans to the
               Architect/WinStar representative for final approval and
               acceptance. The installation of pre-action system shall be in
               accordance with NFPA 13 and manufacturers instructions. The
               following items shall be followed during install:

                    o    Place pipe runs to minimize obstruction to other work.

                    o    Place piping in concealed spaces above finished
                         ceilings if applicable.

                    o    Center sprinklers in one direction only in ceiling tile
                         with location in other direction variable, dependent
                         upon spacing and coordination with ceiling elements.

                    o    Apply masking tape or paper cover to ensure concealed
                         sprinklers, cover plates and sprinkler escutcheons do
                         not receive field paint finish. Remove after painting.
                         Replace painted sprinklers.

                    o    Flush entire piping system of foreign matter.

                    o    Install guards on sprinklers where indicated.

                    o    Hydrostatically test entire system and provide trip
                         test of pre-action system.

                    o    Require test be witnessed by the authority having
                         jurisdiction (local fire marshall), and the A/E.


<PAGE>

                    o    Piping Systems shall be installed as follows:

                    o    Piping mains shall be run close to roof, walls and
                         columns at elevations noted on drawings. Where
                         elevations are not indicated on plans or sections, run
                         as high as other work will permit.

                    o    Coordinate piping runs with work of other trades.
                         Piping shall not interfere with WinStar equipment.

                    o    Pipe lines shall be pitched to allow systems to be
                         drained.

                    o    Reducing fittings (not bushings, orifices, reducing
                         flanges or couplings) shall be provided where pipe size
                         changes. Eccentric reducers shall be provided where
                         necessary to prevent liquid pockets or air binding.

                    o    Drains shall run to hub or floor drains (provided under
                         plumbing work).

                    o    Inspection test connections shall be installed as
                         required by system design.

                    1.1.6.3. Cleaning

                    o    Cleaning and Purging shall be as specified for each
                         service.

                    o    Internal surfaces of piping shall be inspected and kept
                         free of trash, dirt and corrosion.

                    o    Dirty or corroded pipe shall be cleaned to clean, new
                         condition before assembly.

                    o    External surfaces of piping shall be cleaned of dirt,
                         rust scale, grease and other foreign matter, acceptable
                         for painting.

                    1.1.6.4. Painting

                    o    All finished painting of piping shall be done under
                         this section.

                    o    All piping and equipment, whether painted in shop,
                         factory or field, shall be wire brushed and cleaned of
                         dirt, rust, grease and other foreign matter before
                         prime coating.

                    o    All fire protection piping shall be painted Fire
                         Department Red.

                    o    All fire protection piping shall be given two coats of
                         paint, a minimum thickness of 2 mils.


                    1.1.6.5. System Inspections, Start-Up And Testing

                    At the completion of the installation, and after debugging
                    and preliminary testing of equipment had been carried out by
                    the contractor, an on-line "real-time" test of the entire
                    system in the building shall be carried out in the presence
                    of the WinStar construction manager, the manufacturer's
                    representative and the Engineer.

                    1.1.6.6. FM-200 Gaseous Suppression Systems

                    In buildings where fire suppression water is unavailable or
                    of insufficient capacity to support a pre-action suppression
                    system, a gaseous suppression system shall be employed.

                    WinStar standards call for the use of "Dead-man" abort
                    switches and time delays. Abort switches are acceptable only
                    if they are of the "dead-man" type. Keyed abort switches may
                    be installed for security reasons. Time delay should have no
                    more than a 30 second delay program. An abort switch may be
                    used to cycle a time delay. The intent of the time delay is


<PAGE>

                    to allow for: (a) an immediate inspection of the alarmed
                    area (as indicated on the graphic panel) to determine if the
                    fire hazard can be contained locally with a hand held
                    portable fire extinguisher, and (b) to provide additional
                    time to evaluate the room and prepare equipment for
                    discharge.

                    1.1.6.7. FM 200

                    FM 200 is the preferred substitution for Halon suppression
                    systems. There are significant differences between the two
                    systems which must be considered during the design. FM 200
                    is not toxic. FM 200 concentration requirement is greater
                    than Halon (7%) and it employs a discharge time of 10
                    seconds. The pipe sizes are larger and need to be Schedule
                    40 pipe.

                    Certain local regulations do not recognize gaseous fire
                    suppression systems as substitutes for sprinkler systems
                    where required. Other local regulations may require spare
                    gas tanks connected to manifolds for maintained coverage
                    after a system release. The A/E shall consult with the local
                    fire official prior to committing to a design.

                    1.1.6.8. Portable Extinguishers

                    All hub facilities must have a minimum of two type of fire
                    extinguishers on the premises at all times. The first type
                    is a 10lb., class BC, CO2 extinguisher. The CO2 extinguisher
                    should be used first in the event of fires involving
                    equipment cabinets or racks. This will minimize secondary
                    damage caused by chemical agents used in ABC class dry type
                    extinguishers. These agents have alkaline based powders that
                    can be corrosive and cause sever equipment damage. The
                    second type is a class ABC, 5 lb., dry chemical
                    extinguisher. This type should only be used as a last resort
                    on electrical equipment or when the fire has spread to the
                    building structure. The extinguishers shall be located where
                    they will be readily available in the event of a fire. (See
                    architectural section above)

          1.1.7.   RACKS

               o    WinStar has standardized on 23 inch racks for all of its
                    equipment facilities, this is to provide flexibility for new
                    technologies that may be introduced into the network.
                    Wherever possible equipment will be specified at 19 inch,
                    this is to be able to install equipment into existing 19
                    inch facilities or at other service providers sites.

               o    Equipment racks or cabinets shall be 23 x 84 inch EIA/TIA
                    standard, drilled both sides. 

               o    Provide 23 to 19 inch full length rack reducers

               o    Allow a minimum of 36 inches space in front and back of the
                    rack.

               o    Racks shall be lag mounted into a concrete floor on 4
                    corners.

               o    Rack systems require an additional ladder connecting all
                    racks and extending from each end-rack to a wall.

               o    Racks in Hub facilities shall be built in rows.

          1.1.8.   CABLE LADDER SYSTEM

          The hub facility cable ladder system shall be a single-tier ladder
          system with the weight capacity of the system to support 40 lbs/LF
          and, depending on location, must consider the seismic requirements.
          The layout of the cable ladder shall match the configuration of the
          equipment rows. The cable system design shall provide the required 4"



<PAGE>


          separation of cable groups. The following items shall be considered
          during the design:

               o    All ladder and overhead framing must be grounded and bonded

               o    Cable ladder shall have J-hooks extensions to support power
                    and ground cables

          The following cable groups that are required to be separated by a
          minimum of two inches:

               o    Battery and ground (Battery and ground must always be
                    installed in pairs run side by side)

               o    Safety and signal grounds

               o    DS1 transmit and receive cables

               o    DS3 transmit and receive cables

               o    OC interface fiber cabling

               o    Radio cabling

               o    Alarm cables

               o    Cabling from riser coming from the Antenna's

               o    All cabling shall be designed on a 90 degree crossover
                    pattern

          The cable tray system must be laid out and designed to accommodate
          cable distribution throughout the equipment area. Continuity of the
          cable tray system and support for the cables shall be maintained. The
          cable tray system shall be designed with the proper type sections used
          as designed by the manufacturer. Straight sections, elbows, tees,
          dropouts and expansion connectors shall be used as required within the
          system. Cable trays, ladders and troughs may extend through wall or
          floors providing the installation is made so that the possible spread
          of fire or products of combustion will not be substantially increased.
          Openings through fire resistant walls, partitions, floors or ceiling
          shall be sealed using firestop or fire bags.

          Cable tray systems shall be designed to be installed at heights that
          provide clearances adequate to install the necessary equipment with
          provisions for expansion. Factors such as ceiling height, light
          fixture locations, cable entry ports, equipment location and minimum
          cable bending radius must be considered during design and layout.
          Cable trays shall not be placed under smoke detectors or sprinkler
          heads. Cable trays should not be placed under lights or electrical
          fixtures or boxes. It is desirable to have a minimum of 6 inches
          between the top of an equipment rack/cabinet and the bottom of the
          cable tray. It is recommended that there be a minimum of 12 inches
          above the top of the cable tray and the ceiling. AC power cables shall
          not be run within a cable tray system unless they are enclosed within
          metallic conduit or raceway. Equipment drops from cable racks shall be
          from the rack side, not through the rack.

          WinStar Wireless is currently purchasing a complete turnkey cable
          ladder installation for each hub. Fifteen inch cable supported by
          floor mounted tubular supports with unistrut interlocking the system
          to the walls. See figure X for typical install.

          1.1.9.   LOCAL TERMINATION FIELD

          1.1.10.    ANTENNA CONDUIT REQUIREMENTS

          Hub design shall include 2 four inch EMT conduits from the equipment
          room to the surge protector box.


<PAGE>
WINSTAR
                                              WinStar Practice ###-##-####
                                              Issue 2.2 September 1998


                             NSO SITE AND EQUIPMENT
                               TEST AND ACCEPTANCE


1.GENERAL
     1.1.Synopsis

         This practice presents the necessary steps to test and accept
         equipment, products, and sites as they are added to the network. The
         intent of this document is to provide a guideline for standardized
         acceptance criteria.

      1.2.Reason for reissue

         Modification of Acceptance Matrix in Section 2.3 and to the Central
         Office checklist in Attachment 1.

      1.3.Contact for comments

          Comments regarding this document should be directed to either:

                  Tim Precht, Room 2032, 1577 Spring Hill Rd, Vienna VA 22182
                  Telephone (703) 645-5627.   Email: [email protected].

                  or

                  John Alfasi, Room 2027, 1577 Spring Hill Rd, Vienna  VA 22182
                  Telephone (703) 645-5622.   Email: [email protected].


- ------------------------------------------------------------------------------
Not for use or disclosure outside WinStar Communications without the written
permission of WinStar.
- ------------------------------------------------------------------------------
                                     A-4-55
<PAGE>




1.GENERAL...............................................................55

   1.1.SYNOPSIS.........................................................55
   1.2.REASON FOR REISSUE...............................................55
   1.3.CONTACT FOR COMMENTS.............................................55

2.CHECKLIST.............................................................57

   2.1.DESCRIPTION......................................................57
   2.2.ACCEPTANCE CRITERIA..............................................57
   2.3.ACCEPTANCE MATRIX................................................58
   2.4.USING THE CHECKLIST..............................................61
   2.4.ROUTING THE CHECKLIST............................................62
   2.5.NSO PRODUCT/EQUIPMENT ACCEPTANCE CHECKLIST.......................63
   2.6.OVERALL ASSESSMENT:    MANDATORY SECTION.........................66

ATTACHMENT 1............................................................67



- ------------------------------------------------------------------------------
Not for use or disclosure outside WinStar Communications without the written
permission of WinStar.
- ------------------------------------------------------------------------------
                                     A-4-56

<PAGE>


2.CHECKLIST

     2.1.DESCRIPTION

         This document identifies the steps necessary to ensure that new
         additions to the network are properly installed, functional, and
         supportable in the operations environment. The checklist is intended as
         a generic tool to be utilized in assessing network additions prior to
         their acceptance by Network Services Operations.

     2.2.ACCEPTANCE CRITERIA

         The specific requirements for acceptance by NSO will differ based on
         what is being deployed and whether that particular equipment/product
         has been previously deployed. For example, the requirements for
         accepting a Central Office Switch will differ from those for accepting
         a new DCS or Voicemail platform. In general, the following rules can be
         applied:

     o    There should be no duplication of validations that have already
          occurred. NC&D is required to provide NSO with documentation of
          installation and testing at hand-off to NSO. Accountability is
          established via that documentation and acceptance criteria that is
          documented by NC&D should not require further validation. NC&D
          documentation and Test and Acceptance documents should be stored
          centrally with the City Manager for future reference.

     o    All Central Office switches will require documentation of successful
          completion of Integration Testing and ORT for the Engineering plans
          effective at time of delivery. In addition, inspection and validation
          of all physical installations must be recorded on the checklists
          provided in this document.

     o    Equipment installed in Central Offices external to the switch itself
          requires documentation of successful completion of Integration Testing
          along with inspection and validation of the physical installation.


- ------------------------------------------------------------------------------
Not for use or disclosure outside WinStar Communications without the written
permission of WinStar.
- ------------------------------------------------------------------------------
                                     A-4-57
<PAGE>


     2.3.ACCEPTANCE Matrix

         FIELD OPERATIONS REQUIREMENTS FOR ACCEPTANCE


         Using the following matrix: A check (or notation) in a correlating box
         indicates that either documentation of completed work activity must be
         received or completion of the activity itself must be acknowledged by
         the Field Operations group prior to acceptance of the new
         product/equipment in a Central Office.


         Product/Equipment types are listed in generic form (i.e. DXC = any
         digital crossconnect system) meaning that the same requirements apply
         regardless of manufacturer, installer, types of input/output, etc.

<TABLE>
<CAPTION>
                                                          Integration                Ops           Ops
Product/Equipment            Engr Pkg      MOP    CLR     Test Results     ORT       Inspection    Testing
- -----------------------------------------------------------------------------------------------------------
<S>                         <C>            <C>    <C>         <C>          <C>           <C>       <C>  
CAP/LEC Interconnects                              X            X                                    X    
- -----------------------------------------------------------------------------------------------------------
Centrex                        X                                X           X
- -----------------------------------------------------------------------------------------------------------
CLASS Features                 X                                X          FVO                         
- -----------------------------------------------------------------------------------------------------------
Collocated Equipment           X           X      X             X                         X          X  
- -----------------------------------------------------------------------------------------------------------
DXC                            X           X                    X                         X          X
- -----------------------------------------------------------------------------------------------------------
Fiber Terminal                 X           X                    X                         X          X
- -----------------------------------------------------------------------------------------------------------
ISDN                           X                                X          FVO            X          X  
- -----------------------------------------------------------------------------------------------------------
LET                            X           X                    X                         X
- -----------------------------------------------------------------------------------------------------------
LNP                            X                                           
- -----------------------------------------------------------------------------------------------------------
Long Distance                  X                                X          FVO
- -----------------------------------------------------------------------------------------------------------
Switch                         X                                X           X             X          X
- -----------------------------------------------------------------------------------------------------------
Test Equipment                 X          X                     X                         X          X
- -----------------------------------------------------------------------------------------------------------
Trunks (i.e. DA, LD)                      X       X                                                  X
- -----------------------------------------------------------------------------------------------------------
Voicemail                      X          X                     X          FVO            X
- -----------------------------------------------------------------------------------------------------------
</TABLE>


<PAGE>

NOTE: FVO = Field Verification Office meaning that only locations designated FVO
will be ORT tested.

<PAGE>


     2.4.USING THE CHECKLIST

         ------------ -------------------------------------------------------
            STEP                     ACTION
         ------------ --------------------------------------------------------
            2.3.1     The checklist is designed in sectionalized format. These
                      sections may or may not be applicable to the specific
                      product/equipment being assessed. Section titles are
                      followed by the question: "Section Applies?". 

                    o    If the section is not applicable to the current
                         product/equipment check: 

                         No 

                    o    Alternately, if the section does apply check:

                         Yes  

         -------- ------------------------------------------------------------
           2.3.2  Sections that are required for every assessment are noted as
                  "Mandatory Section".

         -------- ------------------------------------------------------------ 

          2.3.3  The final section entitled "Overall Assessment" is intended to
                 provide the rationale for acceptance or rejection of the
                 product/equipment. If a product is rejected the comments 
                 section must contain an explanation of the criteria that was 
                 critical to that rejection. 

                 There are three categories of potential determinations that can
                 result: 

                    1.   Passes all criteria and is determined to be ready for
                         service.

                    2.   Conditionally ready for service with no "service
                         affecting" discrepancies. Items that need to be
                         resolved will be documented and NC&D will provide a
                         timeline for resolution.

                    3.   Not ready for service due to the nature of the
                         deficiencies.

         ------ ---------------------------------------------------------------

         2.3.4  Attachment 1 is provided for use with new Central Office
                acceptances only. This attachment is required prior to
                Central Office acceptance.

<PAGE>



     2.4.ROUTING THE CHECKLIST

         ------ ---------------------------------------------------------------
          STEP                       ACTION
         ------ ---------------------------------------------------------------

         2.4.1   Once the checklist has been completed:

                    1.   a copy should be filed and maintained at the site
                    2.   the original should be forwarded to the Network
                         Construction and Deployment manager responsible for the
                         installation

         ------ ---------------------------------------------------------------

         2.4.2  If the assessment involves a rejection an immediate email
                notification is necessary to:

                    1.   NC&D Manager responsible for installation (from MOP)
                    2.   NC&D Program Management Director (John Resavage)
                    3.   NSO City Manager
                    4.   NSO Regional Director

         ------ ---------------------------------------------------------------

         2.4.3  If the assessment results in an acceptance an email notification
                is necessary to:

                    1.   NSO City Manager
                    2.   NSO Regional Director

                Once the managers agree to acceptance, the NSO Regional
                Director sends an email notification to:

                    1.   Operations Support
                              Debbie Guadalupe ([email protected])
                              Marlene Miller ([email protected])
                    2.   VP, Field Operations (Joe Haggler)

                Operations Support forwards notifications via email to the
                Marketing Distribution list.

<PAGE>


     2.5.NSO Product/Equipment Acceptance Checklist

- ------------------ ---------------------------------- -----------------------
Product/ Equipment:
- ------------------ ---------------------------------- -----------------------
Site/Location:                                        Date:
- ------------------ ---------------------------------- -----------------------

1.0      Rack Installation                     Section applies?   Yes    No

                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         1.1       Mountings                   |_|        |_|          |_|     
         --------- -----------------------------------------------------------
         1.2       Labels                      |_|        |_|          |_|     
         --------- -----------------------------------------------------------
         1.3       Other                       |_|        |_|          |_|     
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------

2.0  Station Ground                             Section applies?   Yes    No

                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         2.1       Grounds                      |_|        |_|          |_|   
         --------- -----------------------------------------------------------
         2.2       Other                        |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------

3.0  Power                                      Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         3.1       Connections                 |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         3.2       Breakers                    |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         3.3       Labels                      |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         3.4       Convenience Outlets         |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         3.5       Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------


<PAGE>

4.0  Alarms                                     Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         4.1       Wiring                      |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         4.2       Labels                      |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         4.3       Functional testing          |_|        |_|          |_|     
                   (Verified visibility with NMC)
         --------- -----------------------------------------------------------
         4.4       Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------


5.0 Card Installation                          Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         5.1       Per design                  |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         5.2       Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------


6.0  Timing                                     Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         6.1       Connections                 |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         6.2       Labels                      |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         6.3       Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------


7.0  Local Craft Interface                      Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         7.1       Connections                 |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         7.2       Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------


<PAGE>

8.0  Remote Access Connection                   Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         8.1       Network (LAN)               |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         8.2       Dial                        |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         8.3       Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------

9.0 TBS Inventory Check                      Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         10.1      Base data built             |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         10.2      Verified 3rd party          |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         10.3      Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------

10.0  Intra-Facility Connections             Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         11.1      Cabling                      |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         11.2      Continuity/Loopback Testing  |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         11.3      Labels                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         11.4      Other                        |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------

11.0  Access Lines                              Section applies?   Yes    No

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         12.1      Access terminations          |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         12.2      Other                        |_|        |_|          |_|    
         --------- -----------------------------------------------------------

         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------

12.0  Functionality                           Mandatory Section

         --------- -----------------------------------------------------------
                   Description               Accept      Defect     Initials
         --------- -----------------------------------------------------------
         13.1      Provisioning mechanisms 
                    operating                  |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         13.2      Operational testing         |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         13.3      Other                       |_|        |_|          |_|    
         --------- -----------------------------------------------------------
         --------- -----------------------------------------------------------
         --------- -----------------------------------------------------------
         Defect
                         ------------------------------------------------------
         Descriptions:
         ---------------------------------------------------------------------

<PAGE>



     2.6.Overall Assessment:                    Mandatory Section

==============================================================================
NOTE: If the current assessment is for a new Central Office, attachment 1A must
also be completed and considered prior to acceptance.
==============================================================================

There are three potential assessment categories:

     1.   Passes all criteria and is determined to be ready for service.

     2.   Conditionally ready for service with no "service affecting"
          discrepancies. Items that need to be resolved will be documented and
          NC&D will provide a timeline for resolution.

     3.   Not ready for service due to the nature of the deficiencies.


    ---------------- ----- -------------------- ------------------------------
    Accepted         |_|       Rejected          |_|
    ---------------- ----- -------------------- ------------------------------
    Comments:
    --------------------------------------------------------------------------

    --------------------------------------------------------------------------

    --------------------------------------------------------------------------

    --------------------------------------------------------------------------

    --------------------------------------------------------------------------

    --------------------------------------------------------------------------


    --------------------- --------------------------------------------------
    Name:
    --------------------- --------------------------------------------------
    Signature:
    --------------------- --------------------------------------------------
    Title:
    --------------------- --------------------------------------------------
    Date:
    --------------------- --------------------------------------------------


<PAGE>


     ATTACHMENT 1



New Central Office Switch

- -------------- ------------------------------ ---------------------------------
CO Name:
- -------------- ------------------------------ ---------------------------------
CLLI Identifier:                              Date:
- -------------- ------------------------------ ---------------------------------


1.  Has NC&D provided a list of outstanding issues and known defects? Yes    No

2.  Has a schedule for correction of defects been provided?           Yes    No

===============================================================================
NOTE: If the answer to either question 1 or 2 is No, STOP. Acceptance of the
Central Office by NSO cannot be considered until these have been provided.
===============================================================================

If items 1-3 outlined in the matrix below are less than "fully operational", CO
Operations can accept the switch as "conditional ready for service but requiring
further resolution by NC&D" as long as this item does not constitute offering
services less than what has been declared acceptable by Marketing. Sign-off from
an authorized representative of Marketing management is necessary to effect this
conditional acceptance.

- ------------------------------------------------------------------------------
          Description                                   Yes   No   Initials
- ----- ------------------------------------------------- ---- ----- ----------
1.    BLV/BLVI operable to Operator Services Provider
- ----- ------------------------------------------------- ---- ----- ----------
2.    E911 services operating
- ----- ------------------------------------------------- ---- ----- ----------
3.    All WinStar NXXs loaded in the switch
- ----- ------------------------------------------------- ---- ----- ----------
4.    Network Facilities and Trunk Groups inventoried
- ----- ------------------------------------------------- ---- ----- ----------
5.    Centest EF&I tested including LAN access
- ----- ------------------------------------------------- ---- ----- ---------
6.    DLC EF&I tested and spare equipment provided
- ----- ------------------------------------------------- ---- ----- ----------
7.    Fiber and CAP facilities tagged
- ----- ------------------------------------------------- ---- ----- ----------
8.    Generator load tested
- ----- ------------------------------------------------- ---- ----- ----------
9.    Rectifier load-sharing equalized
- ----- ------------------------------------------------- ---- ----- ----------
10.   Security card access system verified/alarm detection
- ----- ------------------------------------------------- ---- ----- ----------
11.   Facility clean and ready for operation
- ----- ------------------------------------------------- ---- ----- ----------
12.
- ----- ------------------------------------------------- ---- ----- ----------
13.
- ----- ------------------------------------------------- ---- ----- ----------
14.
- ----- ------------------------------------------------- ---- ----- ----------
Exception
                 ------------------------------------------------------------
Descriptions:
- -----------------------------------------------------------------------------




<PAGE>

WINSTAR
                                              WinStar Practice ###-##-####
                                              Issue 1 March 1998

                     DS-1/DS-3 Certification and Acceptance
                             Performance Objectives



Synopsis

     This practice presents the standards for certification and acceptance of
     the WinStar's DS-1 and DS-3 circuits. The standards are intended to be used
     for both radios, as well as wireline circuits from carriers, CAPs, etc


     Reason for reissue

         N/A

     Contact for comments

         Comments regarding this document should be directed to either:

               Majid Borojeni, 180, 1650 Tysons Blvd, McLean, VA 22102 Telephone
               (703) 790-9246 ext 112. Email: [email protected]. or

               Chris Ball, 2nd Floor, 1577 Springhill Road, Vienna, VA 22182
               Telephone (703) 645-5623. Email: [email protected].






<PAGE>


            DS-1/DS-3 Circuit Certification and Acceptance Objectives

1.0      Objective:

The objective of this document is to provide a set of standards for
certification and acceptance of the WinStar's DS-1 and DS-3 circuits.

The use of these specifications will ensure a quality circuit, that will meet
customer's increasing demands for circuit performance, as well as industry's
performance objectives.

The error performance parameters that will be used during certification and
acceptance tests are: Errored Seconds (ES), Severely Errored Seconds (SES), Bit
Error Rate (BER), and availability objectives.

The Certification test process will be used to test the "transport" link, prior
to having customer circuit assignments. This certification insures that any
impairments are corrected and these facilities meet the minimum performance
requirements. Duration of the certification test should be a 24-hour test period
to reflect the long term effect of the equipment as well as the environmental
effects on this path.

 Acceptance test will use the same test parameters as the certification test,
however, the duration of the test is reduced to one (1) hour. The purpose of the
acceptance test is to detect any degradation in performance which may have
occurred since the certification of the facility, prior to the activation of
customer circuits.

It should also be noted that the Bit Error Rate test by itself can not be used
to describe the health of the transport. The reason being that, usually BER
occurs in burst, therefore, is not indicative of the overall health of the
transport network. In today's data oriented environment, and customers'
increasing demands for error free facilities, performance parameters such as ES
and SES must be used for finding the overall error distribution.


<PAGE>


2.       Definitions:

Bit Error Ratio (BER): The ratio of the number of bit errors to the total number
of bits transmitted in a given time interval.

Errored Second (ES): A one second interval with one or more bit error.

Error Free Second (EFS): A one second interval in which no bit errors are
received. This parameter is measured in percentage.

Severely Errored Second (SES): A one second interval having a bit error ratio of
1xe-3 or worse.

Outage: An outage, usually measured in `outage second", is declared after 10
consecutive SESs have occurred. Outage seconds are counted until 10 consecutive
non-SESs occur.

Availability: Availability refers to that time which the circuit is available,
that is not experiencing an outage. Usually this termed is expressed as percent
availability by taking the ratio of the available time during a given interval
to the total interval.


3.0      DS-3 Certification Link Objectives (24-hour test period)

          This is a test for a newly installed DS-3 radio or a DS-3 hand-off
          from other carriers. This test should be done at the DSX-3 point. This
          is a looped back test at the DSX-3 panel from the remote location.

         Errored Seconds (ES) less than or =                2 
         Error Free Seconds % (EFS%) greater than           99.998%
         Severely Errored Seconds (SES) =                   0 
         Bit Error Ratio (BER, QRS test) less than          1xe-9


3.1      DS-3 Acceptance Link Objectives (not required)

          At the present time, once the customer orders a DS-3 circuit, the
          certification test will also serve as an acceptance test. A DS-3
          acceptance test will be required in the future with the deployment of
          OC-3 type SONET radios.



<PAGE>


4.0      DS-1 Certification Link Objectives (24-hour test period)

          This is a test for a newly installed 8x or 4x DS1 radios or a DS-1
          hand-off from other carriers. This test should be done at the DSX-1
          point. This is a looped back test at the DSX-1 panel from the remote
          location.

         Errored Seconds (ES) less than or =                1 
         Error Free Seconds % (EFS%)greater than            99.999%
         Severely Errored Seconds (SES) =                   0 
         Bit Error Ratio (BER, QRS test) less than          1xe-9


  4.1    DS-1 Acceptance Objectives (1-hour test period)

          This test should be done every time we are turning up a DS1 off of the
          DS1 radios or off of the DS-3 radios via the MUX equipment at the
          DSX-1 panel

          QRSS pattern should be selected for this test to verify the health of
          the network, once the following objectives are met the additional 15
          minutes stress test must be done before the circuit is accepted and
          handed off to the customer.

         Errored Seconds (ES):                              0
         Error Free Seconds(EFS%):                          100%
         Severely Errored Seconds (SES):                    0
         Bit Error Ratio (BER) less than                    1xe-9

4.1.1    DS-1 Acceptance Objectives (15 minutes stress test)

          In addition to the above acceptance test the following stress test
          patterns should be performed. The test should be a loop test at the
          CSU (if available) or at the RJ48X jack, or equivalent DS1 termination
          point. The objectives of these stress test patterns are to isolate any
          mis-optioning that might exist in the network prior to customer
          activation. The length of each pattern should be five minutes.



         Stress Test Pattern (AMI):

                  TEST               TIME              ERRORS

                  3 in 24           5 minutes             0
                  All  Ones         5 minutes             0
                  55 Octet          5 minutes             0

<PAGE>

Note:  Other stress pattern tests such as 2^15-1, 2^20-1, 2^23-1 could be used 
for fault isolation purposes.

         Stress Test Pattern (B8ZS):

                  TEST                 TIME            ERRORS

                  3 in 24           5 minutes            0
                  All 0s            5 minutes            0
                  All Ones          5 minutes            0
                  55 Octet          5 minutes            0



          Note: Other stress pattern tests such as 2^15-1, 2^20-1, 2^23-1 could
          be used for fault isolation purposes.


<PAGE>

                                   Exhibit A-5

                           Hub Implementation Forecast

<TABLE>
<CAPTION>
- -------------- ------------------- ---------------- ------------------ ---------------------
    Month        Hubs Delivered      Percent of      Hubs Delivered      Percent of Total
                                     Total Hubs          to Date           Hubs to Date
- -------------- ------------------- ---------------- ------------------ ---------------------
<S> <C>                <C>              <C>                <C>                <C>   
Dec-98                 57               21.11%             57                 21.11%
Jan-99                 --                0.00%             57                 21.11%
Feb-99                 --                0.00%             57                 21.11%
Mar-99                 18                6.67%             75                 27.78%
Apr-99                 --                0.00%             75                 27.78%
May-99                 --                0.00%             75                 27.78%
Jun-99                 25                9.26%             100                37.04%
Jul-99                 --                0.00%             100                37.04%
Aug-99                 --                0.00%             100                37.04%
Sep-99                 25                9.26%             125                46.30%
Oct-99                 --                0.00%             125                46.30%
Nov-99                 --                0.00%             125                46.30%
Dec-99                 25                9.26%             150                55.56%
Jan-00                 --                0.00%             150                55.56%
Feb-00                 --                0.00%             150                55.56%
Mar-00                 20                7.41%             170                62.96%
Apr-00                 --                0.00%             170                62.96%
May-00                 --                0.00%             170                62.96%
Jun-00                 20                7.41%             190                70.37%
Jul-00                 --                0.00%             190                70.37%
Aug-00                 --                0.00%             190                70.37%
Sep-00                 20                7.41%             210                77.78%
Oct-00                 --                0.00%             210                77.78%
Nov-00                 --                0.00%             210                77.78%
Dec-00                 20                7.41%             230                85.19%
Jan-01                 --                0.00%             230                85.19%
Feb-01                 --                0.00%             230                85.19%
Mar-01                 10                3.70%             240                88.89%
Apr-01                 --                0.00%             240                88.89%
May-01                 --                0.00%             240                88.89%
Jun-01                 10                3.70%             250                92.59%
Jul-01                 --                0.00%             250                92.59%
Aug-01                 --                0.00%             250                92.59%
Sep-01                 10                3.70%             260                96.30%
Oct-01                 --                0.00%             260                96.30%
Nov-01                 --                0.00%             260                96.30%
Dec-01                 10                3.70%             270               100.00%
- -------------- ------------------- ---------------- ------------------ ---------------------
    TOTAL             270                 100%             270                  100%
- -------------- ------------------- ---------------- ------------------ ---------------------
</TABLE>


<PAGE>

                                   Exhibit A-6

                              Williams Connectivity

     1.1. Definitions

          The following terms shall have the meanings set forth herein:

          (a)  "Minimum Williams T-1 Inventory" means the aggregate, cumulative
               Williams T-1s that WinStar commits to provide to Williams as
               described herein.

          (b)  "Williams T-1 Ceiling" means the maximum cumulative amount of
               Williams T-1s that Williams is entitled to use in any given
               calendar year, which shall equal 1.5 multiplied by such year's
               Estimated T-1 Inventory, up to a cap of 95,355 Williams T-1s.
               Such cap shall in no event be exceeded except as expressly
               provided for herein.

          (c)  "Estimated T-1 Inventory" means the non-binding estimate of the
               cumulative number of Williams T-1s that may be available in a
               certain calendar year. The Estimated T-1 Inventory is provided
               for illustrative purposes only.

          (d)  "Williams Connectivity" means two percent (2%) of the Domestic
               Hub Capacity, which is the quantity to be allocated to Williams,
               as may be subsequently modified by written agreement of the
               Parties.

          (e)  "Technology Fee" means the amount that Williams shall pay in
               order to exceed the Williams T-1 Ceiling and have the right to
               obtain up to the full amount of the Williams Connectivity. The
               Technology Fee shall be equal to Williams' Pro-Rata Share of all
               Costs associated with any upgraded technology deployed by
               WinStar.

                      [CHART DIAGRAMMING INVESTORY LEVELS]


          1.2. Operation.

          Upon the Effective Date and for each calendar year beginning with the
          calendar year 2000, WinStar will provide to Williams the greater of
          the Williams Connectivity, subject to the Williams T-1 Ceiling, and
          the Minimum Williams T-1 Inventory. Beginning on the first day of the
          calendar year 2008, the Minimum Williams T-1 Inventory and the
          Williams T-1 Ceiling shall both remain constant (i.e. at 2008 levels)
          for the remainder of the Term.




<PAGE>
                                   Schedule B

                              Performance Standards
1.       General

          1.1. General. 

               The performance standards set forth in this Schedule are intended
               to measure WinStar's performance with regard to two specific
               areas: Problem Resolution and Circuit Availability. 

1.2.      Definitions. 

          (a)  "Actual Uptime" of a circuit shall mean the period that such
               circuit is actually available for normal transport (i.e.,
               Scheduled Uptime - outage) plus any time of outage due to a force
               majeure event or third party equipment, transport or services.
               
          (b)  "Availability" of a circuit shall mean the Actual Uptime
               expressed as a percentage of the Scheduled Uptime for such
               circuit (i.e., Availability % = (Actual Uptime)/Scheduled Uptime
               * 100%). 

          (c)  "Scheduled Uptime" shall mean that period of time (days of the
               week and hours per day) during which a circuit is expected to be
               available for normal transport. 

          (d)  "Time to Respond" shall mean the elapsed time between
               registration of a problem (e.g., through notification by
               Williams' Network Customer Care) or service request to WinStar
               and the commencement of efforts.

2. problem resolution 

2.1.      General. 

          WinStar shall resolve problems with the Williams T-1s as quickly as is
          practicable but, at a minimum, shall use commercially reasonable
          efforts to meet the standards set forth in Section 2.3.

2.2. Measurement. 

          The problem classifications are as follows:

(a) Priority Level 1: A problem that causes Outage of
               multiple Williams T-1s. 

(b) Priority Level 2: A problem that
               causes Outage of one Williams T-1 or degrades performance of
               multiple Williams T-1s. 

(c) Priority Level 3: A problem that
               causes degradation of performance of one Williams T-1. 

2.3.      Performance. 

          Priority Level Objectives:
          
                    Priority Level           Mean Time to Respond
               -------------------------     ------------------------
                          1                       Four (4) hours 
                          2                       Eight (8) hours 
                          3                       Twelve (12) hours

3.   Circuit Availability. 

     3.1. General.

          WinStar shall attain the performance standards set forth in Section
          3.3. 

     3.2. Measurement. 

          Availability of the Williams T-1s shall be measured as the average
          Availability of all WinStar Wireless Fiber Connectivity circuits. 

     3.3. Performance Objective. 

          (a)  WinStar shall achieve a Wireless Fiber Connectivity Availability
               of at least 99.95%.

          (b)  A circuit is considered inoperative when there is a loss of
               signal or when its bit error rate is equal to or worse than 1.0 x
               10-3.

<PAGE>
                                   Schedule C

                                     Charges
1.       General

         This Schedule C describes the charging methodologies and processes for
         the Wireless Fiber Connectivity that WinStar will provide to Williams
         under the terms and subject to the conditions of the Agreement.

2.       Williams' payment commitments

         2.1.     Payment for Hubs.

                  As consideration for the Williams Connectivity, Williams shall
                  pay One Million, Four Hundred Eighty-One Thousand, Four
                  Hundred and Eighty-One Dollars ($1,481,481) upon Acceptance of
                  each Hub, up to a maximum of Four Hundred Million Dollars
                  ($400,000,000) over the Term. This payment shall be made
                  thirty (30) days following Acceptance of the corresponding
                  Hub.

     2.2. Additional Wireless Fiber Connectivity.

          Subject to Sections 6.4 (Most Favored Customer) and 6.5 (Benchmarking)
          of the Agreement, WinStar shall price Wireless Fiber Connectivity
          purchased by Williams in excess of the Williams Connectivity, if any,
          at WinStar's then-current standard rates. Nothing set forth in this
          Schedule C shall be deemed to obligate WinStar to sell more Wireless
          Fiber Connectivity than the Williams Capacity. 

     2.3. Maintenance

          Services. Williams shall pay for the Routine Maintenance Services (as
          defined in Schedule A) delivered over the Term with regard to the
          Williams T-1s at a rate of Three Hundred Eighty Thousand, Twenty-Seven
          Dollars ($380,027) per month for the period between January, 1998 and
          December 2008, inclusive. Charges for up to Five Thousand Dollars
          ($5,000) worth of non-routine maintenance per Williams T-1 are also
          included in such rate. Charges for Routine Maintenance Services for
          other Wireless Fiber Connectivity purchased by Williams shall be
          priced at WinStar's then-current standard rates, subject to Sections
          6.4 and 6.5 of the Agreement. 

     2.4. Collocation Services. 

          Charges for Collocation Services with regard to the Williams
          Connectivity are included in the pricing set forth in Sections 2.1 and
          2.2 of this Schedule C. Charges for Collocation Services for other
          Wireless Fiber Connectivity purchased by Williams shall be priced at
          WinStar's then-current standard rates, subject to Sections 6.4 and 6.5
          of the Agreement.






                       AGREEMENT TO PURCHASE LMDS LICENSE



         AGREEMENT  TO PURCHASE  LMDS  LICENSE,  dated as of July 10, 1998 (this
"Agreement") by and between WinStar Communications, Inc., a Delaware corporation
the "Purchaser"), CellularVision USA, Inc., a Delaware corporation ("CVUSA") and
CellularVision of New York, L.P., a Delaware limited partnership ("Seller"),

         WHEREAS, Seller holds the LMDS A Block License (the "License") from the
Federal  Communications   Commission  (the  "FCC")  for  the  New  York  Primary
Metropolitan  Statistical Area (i.e.,  the five boroughs  comprising the City of
New York, and the contiguous  New York State counties of  Westchester,  Rockland
and  Putnam),  free and  clear of all  liens,  claims,  rights of usage by third
parties and other encumbrances (collectively, "Liens"),

         WHEREAS, Seller and CVUSA have retained Wasserstein Perella & Co., Inc.
to advise them on the marketing and sale of the 850 MHz License and  Wasserstein
Perella & Co., Inc. has managed the sale process,  which  included,  among other
things,  contacting  a large number of  potential  purchasers  as well as active
negotiations  with certain  potential  purchasers,  all of which resulted in the
offer of the Purchase  Price and the Loans (as  hereinafter  defined) all on the
terms and  conditions  set forth herein,  which CVUSA deems to be the best offer
currently available for the 850 MHz License;

         WHEREAS, Seller intends to disaggregate 850 MHz of the spectrum covered
by the License,  comprised of the frequencies  between 27.5 and 28.35 GHz and to
be conveyed to Purchaser  pursuant to a license  granted by the FCC thereto (the
"850 MHz License") and  Purchaser  wishes to purchase the 850 MHz License,  upon
the terms and subject to the conditions set forth herein,  free and clear of all
Liens.

         WHEREAS,  holders of a  majority  of the  outstanding  shares of common
stock  of  CVUSA  wish  to  irrevocably   consent  to  this  Agreement  and  the
transactions contemplated hereby;

<PAGE>

         NOW,  THEREFORE,  in  consideration  of the  premises,  and the  mutual
conditions and obligations set forth herein,  the parties hereto hereby agree as
follows:

         1. Purchase Price; Loan. (a) The purchase price for the 850 MHz License
shall be $32,500,000,  of which a portion will be payable by offset of the total
outstanding principal amount and accrued interest on the Loan (as defined below)
and the  remainder  of which  will be payable by wire  transfer  of  immediately
available funds to Seller at the Closing (defined in Section 3).

         (b) As promptly as practicable  following the execution and delivery of
this Agreement by the parties hereto  (including the voting agreement of certain
holders  owning not less than 39% of the  outstanding  shares of common stock of
CVUSA),  Purchaser  will make an initial loan to Seller (the "Initial  Loan") in
the amount of  $3,500,000,  and,  when  Seller  shall have made the FCC  filings
contemplated  by Section  2(a) and CVUSA  shall have  obtained  the  stockholder
approval  contemplated by Section 13,  Purchaser will make an additional loan in
the amount of  $2,000,000  (such loan,  together  with the Initial  Loan and the
loans that  Purchaser may, in its sole  discretion,  make pursuant to Section 6,
the "Loans") at 7.5% per annum,  with interest and principal  payable in full at
the Closing by way of offset  against the  purchase  price then due, as provided
above, or on such earlier date as this Agreement may be terminated in accordance
with its terms, provided that in the event of such a termination,  such interest
rate  will be 18% per  annum.  The Loans  will be  secured  by a first  priority
perfected  security  interest  on all of the  assets  of  Seller  as to  which a
security interest may be granted,  including,  without limitation,  the proceeds
from such assets as well as from the sale or other transfer of FCC licenses,  it
being  understood  and agreed that (i) a vendor's  security  interest in certain
equipment has been assigned to NewStart Factors,  Inc. and (ii) the FCC licenses
may not be  subject  to  security  interests  as a  matter  of law.  Purchaser's
security  interest  will  extend to  after-acquired  property  and to  proceeds,
provided that Borrower will retain the right to enter into vendor  financing and
equivalent  secured financing  arrangements  with respect to equipment  acquired
after the date hereof.  CVUSA will  guarantee the repayment in full of the Loans
in accordance with its terms, and will secure its guarantee with a pledge of all
of the outstanding  shares of stock of  CellularVision  Capital Corp.,  the sole
general  partner  of  Seller,  and all of the  outstanding  limited  partnership

                                       2
<PAGE>

interests  in  Seller,  all of which are owned by CVUSA.  The  parties  agree to
prepare,  review  and  negotiate  in good  faith  and  execute  as  promptly  as
practicable  (and in any  event  prior to the  funding  of the  Loans)  mutually
acceptable  definitive  documentation  ((the "Loan Documents") in customary form
for  these  financing  transactions,   including,  without  limitation,  a  Loan
Agreement  (including  guaranty  provisions),   a  Note,  a  Security  Agreement
(including  pledge  provisions),  and UCC-1  forms.  To the  extent  there is an
inconsistency  between the Loan Documents and this Agreement with respect to the
Loans and related security arrangements, the Loan Documents shall control.

         2.  Government  Approvals;  Transition.  (a) As promptly as practicable
following  the execution  and delivery of this  Agreement,  Seller and Purchaser
will (i) file appropriate applications for the disaggregation of the License and
assignment  of the 850 MHz License to Purchaser and (ii) make such filings under
the  Hart-Scott-Rodino  Antitrust  Improvements  Act of 1976 and the  rules  and
regulations (collectively, the "HSR Act") as may be legally required in order to
consummate the transactions  contemplated herein, with the filing fee related to
any such filing to be shared by Purchaser and CVNY on a 50%/50% basis. Following
the making of such  applications  and  filings,  both  parties  will  diligently
attempt to obtain  successful  results  with  respect  thereto in a manner  that
permits the  consummation  of the  transactions  contemplated  herein as soon as
practicable.

                  (b)  Prior  to  the  Closing,   and  in  accordance  with  all
applicable legal and regulatory  requirements,  Seller will clear its operations
from  the  spectrum  covered  by the  850 MHz  License,  such  transition  to be
completed  in any event  within 90 days of the date of FCC  Approval  (as herein
defined).

         3. Closing.  The closing of the transactions  contemplated  herein (the
"Closing")  shall occur on the first business day (the "Closing Date") following
the first date upon which all of the following conditions are satisfied: (i) the
FCC shall have granted its consent to the  assignment  of the 850 MHz License to
Purchaser  and,  unless  waived by  Purchaser,  such consent shall have become a
final,  nonappealable order no longer subject to review or reconsideration ("FCC

                                       3
<PAGE>


Approval"); (ii) CVUSA shall have obtained the approval of its stockholders with
respect  to the  transactions  contemplated  hereby;  and (iii)  any  applicable
waiting  period  under the HSR Act shall have  expired  without  action taken to
prevent  the  consummation  of  the  transactions  contemplated  herein.  At the
closing,  Seller shall assign the 850 MHz License to Purchaser free and clear of
all Liens against payment of the Purchase Price as contemplated by Section 1.

         4.  Representations and Warranties.  (a) Each party (the "Representer")
hereby  represents  and warrants to the other that (i) the  Representer  has all
requisite  power and authority to execute this  Agreement and the Loan Documents
and perform its  obligations  hereunder and  thereunder,  (ii) all corporate and
partnership action necessary for the authorization, execution and performance by
the  Representer of its  obligations  hereunder and thereunder  have been taken,
except that,  in the case of CVUSA,  stockholder  approval may be required,  and
(iii) subject to obtaining the consent and approvals  referred to in paragraph 3
above,  the execution,  delivery and  performance of this Agreement and the Loan
Documents  does not and will not  require  the  consent  of any other  person or
entity, contravene the certificate of incorporation or by-laws or certificate of
limited partnership or partnership agreement of the Representer or conflict with
or result in a breach  or  violation  by the  Representer  of any law,  court or
administrative order or contract to which the Representer is a party or by which
the Representer is bound.

         (b) Seller and CVUSA  hereby  represent  and warrant that Seller is the
sole legal and beneficial  owner and holder of the License,  has the right under
applicable  law and FCC  regulations  to effect the  disaggregation  of spectrum
contemplated  hereby and that the License  is, and the 850 MHz License  will be,
held by Seller  free and clear of all Liens.  Without  limiting  the  foregoing,
Seller hereby represents and warrants that no person or entity other than Seller
has or will have the right to use all or any  portion of the  License or the 850
MHz License.  Seller hereby  further  represents  and warrants that (i) it is in
compliance  in all material  respects  with the  Communications  Act of 1934, as

                                       4
<PAGE>

amended,  and the rules,  regulations  and policies of the FCC,  (ii) Seller has
satisfied all build-out,  renewal,  construction  and other material  regulatory
requirements, and (iii) there are no pending complaints,  challenges, petitions,
appeals  or  other  regulatory  encumbrances  pending  or,  to the  best  of the
knowledge of Seller or CVUSA, threatened, against Seller or the License.

         (c) Each party will use all  commercially  reasonable  efforts to cause
all of its  representations  and warranties in this Agreement to remain true and
correct at all times  through the Closing  Date and to cause all  conditions  to
Closing to be satisfied.

         5. Closing  Conditions.  (a) Each Party's  obligation to close shall be
subject to the following  conditions (i) the other party's  representations  and
warranties  hereunder and under the Loan Documents  shall be true and correct on
and as of the Closing  Date as if made again on that date,  (ii) the other party
shall  have  performed  all  covenants  to have  been  performed  hereunder  and
thereunder  and (iii) the other party shall have  delivered a  certificate  of a
senior  officer as to the  matters in clauses (i) and (ii) above dated as of the
Closing Date.

         (b) Purchaser's  obligation to close shall be subject to the conditions
that (i) the  conditions  referred  to in  Sections  2(b) and 3 shall  have been
satisfied, (ii) there shall be no injunction or order of any court or government
agency restraining or invalidating any of the transactions  contemplated hereby,
and (iii) Purchaser shall have received opinions of Seller's counsel dated as of
the date  hereof and as of the  Closing  date in form and  substance  reasonably
satisfactory  to Purchaser and covering  such portion of the matters  covered by
Seller's and CVUSA's representations contained herein as are customarily covered
in legal opinions and subject to customary qualifications,  including an opinion
of FCC counsel substantially in the form attached.

         6.  Termination.  Either party which is not then in material  breach of
its  obligations  hereunder may terminate  this Agreement  without  liability by
written notice to the other party if the Closing Date shall not have occurred on
or before January 31, 1999,  provided,  however,  that upon  Purchaser's  notice

                                       5
<PAGE>


given at least 10 days prior to the date that  termination  would  otherwise  be
permitted,  such date shall be  extended to June 30,  1999 and,  thereafter,  to
December 31, 1999 if (i) Purchaser is not in material  breach of its obligations
hereunder and (ii) on each such occasion  Purchaser  makes an additional Loan of
$3.5 million in principal amount to the Seller on  substantially  the same terms
as the Loans.  Purchaser may terminate  this  Agreement at any time if CVUSA has
not obtained stockholder approval of this transaction by October 10, 1998.

         7. Transaction  Expenses.  Except as otherwise provided in Section 2(a)
and  Section 13, each of the  parties  hereto  will be  responsible  for its own
expenses  (including fees and expenses of legal counsel)  incurred in connection
with the transactions  contemplated hereby, provided that as of the Closing Date
(or earlier termination of this Agreement in accordance with its terms in a case
in which the expense reimbursement  provision of Section 13 do not apply) Seller
and CVUSA will  reimburse  Purchaser's  reasonable  fees and expenses of counsel
incurred in connection  with the  negotiation  and  preparation of the documents
relating to the transactions  contemplated hereby,  including the Loans, and the
prosecution  of the FCC  applications  contemplated  hereby,  provided  that the
amount  of  such  fees  and  expenses  related  to  the   documentation  of  the
transactions  through the funding of the Initial Loan and prosecution of the FCC
applications contemplated hereby shall not exceed $50,000. Each party represents
to the other that it has not incurred any  liability  for a broker's or finder's
fee in connection with the transactions  contemplated hereby, except that Seller
is liable to  Wasserstein  Perella & Co., Inc. for fees in connection  with such
transactions.

         8.  Publicity;  Disclosure.  Without  the prior  approval  of the other
party,  neither of the  parties  hereto  shall  disclose to the public or to any
third party any information  concerning the  transactions  contemplated  hereby,
other than  disclosures  to their  financial,  legal and other  advisors  and to
governmental  authorities  or the public as may, in the  opinion of counsel,  be
required by law.  Notwithstanding  the  foregoing,  CVUSA shall be  permitted to
include in the proxy statement  described in Section 13 hereof,  such details of
the transactions  contemplated  hereby as may be required by law;  provided that


                                       6
<PAGE>


Purchaser  shall have the right to review and comment thereon prior to the proxy
statement being filed with the SEC or distributed. The parties will cooperate in
the  preparation  of a joint press  release or  coordinated  but separate  press
releases  announcing  the  effectiveness  of this Agreement as soon as it occurs
pursuant to Section 12.

         9. Access. Until the Closing,  CVUSA and Seller will give Purchaser and
its  representatives  all access during ordinary  business hours to the premises
and  personnel of Seller and CVUSA and to all  accounting,  financial  and other
records applicable to Seller as Purchaser may reasonably request for the purpose
of  confirming  compliance  with this  Agreement and CVUSA and shall furnish all
information  with respect to the business and affairs of Seller as Purchaser may
reasonably  request  for  such  purpose.  CVUSA  and  Seller  will  cause  their
executives, employees, attorneys and accountants to make themselves available to
provide reasonable cooperation to Purchaser in connection therewith.

         10.  Exclusivity.  Neither  CVUSA nor Seller shall (nor shall either of
them permit their  representatives  or stockholders to) discuss a possible sale,
lease or other disposition of or by Seller or CVUSA (whether by sale of stock or
assets or otherwise)  that is not  consistent  with the sale to Purchaser of the
850 MHz License  contemplated  hereby or provide any  information  in connection
therewith to any other party or enter into any  agreements or  commitments to do
the same.

         11.  Assignment.  This Agreement is intended to be a binding  agreement
between  Purchaser,  CVUSA and Seller and shall bind and inure to the benefit of
the successors  and assigns of such parties;  provided that CVUSA and Seller may
not  assign  their  rights  or  delegate  their  obligations  hereunder  without
Purchaser's prior written consent,  which will not be unreasonably withheld. The
Purchaser may assign its rights hereunder to any of its wholly-owned or majority
controlled  subsidiaries,  provided that no such  assignment of its rights shall
relieve Purchaser of any of its obligations hereunder.

                                       7
<PAGE>


         12.  Effectiveness.  Simultaneously  with the execution and delivery of
this Agreement the following are expected to occur, upon the occurrence of which
this Agreement will come into full force and effect:

                  (a) Holders of not less than 39% of the issued and outstanding
shares of Common  Stock of CVUSA  shall  have  agreed  to vote  their  shares as
provided below;

                  (b) Seller shall have  executed and delivered to Purchaser the
Loan Documentation,  including arrangements with existing creditors as Purchaser
shall deem appropriate;

                  (c)  Purchaser  shall have  received such opinions of Seller's
counsel as it shall  reasonably  require in  connection  with FCC and  corporate
matters with  respect to the Loan  Documents,  the License and the  transactions
contemplated  hereby,  including,  if Purchaser so requires, a favorable opinion
from Purchaser's FCC counsel to the effect that there is no reason to expect (i)
that the transactions  contemplated hereby will materially  adversely affect the
regulatory  status  of  any of the  FCC  wireless  licenses  currently  held  by
Purchaser or any of its subsidiaries or (ii) that there is any reason to believe
that the disaggregation of spectrum is not permissible under applicable law.

         13.      Shareholder Approval; Break-up fee; Events of Bankruptcy.

                  (a) CVUSA has obtained the approval of a majority of its board
of  directors  to the  transactions  contemplated  hereby,  and  its  board  has
recommended and will continue to recommend,  so long as such  recommendation  is
consistent  with  their  fiduciary   duties  under   applicable  law,  that  its
stockholders vote to approve the transactions  contemplated  hereby.  CVUSA will
call a special  meeting of its  stockholders  as promptly as practicable for the
purpose of obtaining such approval, will file a preliminary proxy statement with
respect  thereto with the  Securities  and Exchange  Commission  within five (5)
business  days  of the  execution  of  this  Agreement  and  will  distribute  a
definitive  proxy  statement to  stockholders in accordance with applicable law,
and use its best  efforts to hold such  meeting  and  obtain  such  approval  as
quickly as possible.


                                       8
<PAGE>

                  (b) In the event a petition for relief under 11 U.S.C.  ss.101
et seq. (the "Bankruptcy Code") or similar State insolvency statute, is filed by
or against Seller or CVUSA,  each Seller and CVUSA agree to (i) consent to entry
of an order for relief under Chapter 11 of the Bankruptcy Code; (ii) continue to
comply with the terms of this Agreement;  and (iii) to the extent  necessary for
Seller or CVUSA to  continue to comply  with the terms of this  Agreement,  seek
Bankruptcy  Court  approval of the sale  contemplated  by this Agreement or take
such other  action as may be necessary or advisable to allow Seller and CVUSA to
continue to comply with the terms of this Agreement.

                  (c) in the event at any time on or prior to the  Closing  Date
(i) this Agreement is terminated by Seller or CVUSA (other than as a result of a
material breach by Purchaser) and a court  determines that specific  enforcement
in  accordance  with  the  provisions  of  Section  14(b)  is not  available  to
Purchaser, or (ii) Purchaser terminates this Agreement because CVUSA stockholder
approval has not been  obtained by October 10,  1998,  then  Purchaser  shall be
entitled to the following as liquidated damages, and not as a penalty:

                  (i)  Expense  Reimbursement:  Seller  and  CVUSA  jointly  and
severally shall reimburse Purchaser for its actual and reasonable  out-of-pocket
expenses,  not to exceed $325,000  (exclusive of the amounts payable pursuant to
Section 7)  incurred  in  furtherance  of this  Agreement  and the  transactions
contemplated herein, including without limitation,  attorneys' fees and expenses
incurred by  Purchaser  for  services  of outside  counsel in  negotiating  this
Agreement,  the Loan  Documents and all related  agreements,  performance of due
diligence, or otherwise (the "Expense Reimbursement"). Purchaser shall submit to
Seller  and  CVUSA an  itemized  statement  reflecting  such  actual  reasonable
expenses.  Within  five (5) days  thereafter,  Seller  and CVUSA  shall  make an
Expense  Reimbursement.  This  obligation  shall survive any termination of this
Agreement,  and shall be secured by the collateral under the security  agreement
being executed in relation to the Loans.


                                       9
<PAGE>

                  (ii)  Termination  Fee. Seller and CVUSA jointly and severally
shall, within five (5) days of such termination, pay $1,625,000 to the Purchaser
as a termination fee  ("Termination  Fee").  This  obligation  shall survive any
termination of this Agreement,  and shall be secured by the collateral under the
security agreement being executed in relation to the Loans.

         14. Specific  Performance;  Miscellaneous;  Conflict  Waiver.  (a) This
Agreement  shall be construed and enforced in accordance  with the internal laws
of the  State of New York.  This  Agreement  may be  executed  in any  number of
counterparts,  each of which  shall be an  original,  but which  together  shall
constitute one instrument.

                  (b)  Notwithstanding  the  provisions of Section  13(c)(i) and
(ii),  it is  understood  and agreed that money damages would not be an adequate
remedy for a breach of the Agreement by Seller or CVUSA and that Purchaser shall
be entitled to specific  performance and injunctive or other equitable relief as
a remedy for any such  breach.  Seller and CVUSA agree to waive any  requirement
for the securing or posting of any bond in  connection  with such  remedy.  Such
remedy shall not be deemed to be the exclusive  remedy for any such breach,  but
shall be in addition to all other  remedies  available to Purchaser at law or in
equity.

                  (c) Each of the parties hereto  acknowledges that Willkie Farr
& Gallagher regularly acts as counsel for each of them, and consents to the fact
that the New York  office  of such  firm will  provide  corporate  (but not FCC)
advice to CVUSA and Seller  (which will receive FCC advice from other  counsel),
its Washington  office will provide FCC (but not corporate) advice to Purchaser,
which is also represented by other counsel in this matter.

                            [Signature page follows]


<PAGE>




     IN WITNESS WHEREOF,  the undersigned have executed this Agreement as of the
date first above written.




                          WINSTAR COMMUNICATIONS, INC.



                            By:/s/ Timothy R. Graham
                            --------------------------
                                Timothy R. Graham
                            Title:


Accepted and agreed as of July 10, 1998


CELLULARVISION USA, INC.




By:_/s/ Shant Hovnanian
- -------------------------
   Printed name: Shant Hovnanian
   Title:

         CELLULARVISION OF NEW YORK, L.P.

         By: CELLULARVISION CAPITAL CORP.,
                  its General Partner

         By:___/s/ Shant Hovnanian
          --------------------------
                  Title:


                                       11

<PAGE>

         Voting Agreement by Stockholders

         In  consideration  of  the  Purchaser  executing  the  Agreement,   the
undersigned,  being the holders of not less than 39%  outstanding  shares of the
voting capital stock of CellularVision USA, Inc. which is entitled to vote a the
approval of the transactions  described herein, hereby expressly and irrevocably
agree  to vote  all  such  shares  in  favor  of  approval  of the  transactions
contemplated hereby at any special meeting of stockholders to be called for such
purpose and do hereby  agree to take such actions as  Purchaser  may  reasonably
request in order to further evidence such approval and consent.



                                                     /s/ Shant Hovnanian
                                                     ---------------------
                                                     Shant Hovnanian



                                                     /s/ Vahak Hovnanian
                                                     --------------------
                                                     Vahak Hovnanian


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