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OMB APPROVAL
UNITED STATES OMB Number. 3235-0145
SECURITIES AND EXCHANGE COMMISSION Expires: August 31, 1991
WASHINGTON, D.C. 20549 Estimated average burden
hours per response 14.90
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(AMENDMENT NO. )*
Natural Microsystems Corp.
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(Name of Issuer)
Common Stock
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(Title of Class of Securities)
63888210
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Check the following box if a fee is being paid with the statement [X]. (A fee
is not required only if the filing person: (1) has a previous statement on file
reporting beneficial ownership of more than five percent of the class of
securities described in Item 1; and (2) has filed no amendment subsequent
thereto reporting beneficial ownership of five percent or less of such class.)
(See Rule 13d-7).
*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.
The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).
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CUSIP No. 63888210 13G PAGE 2 OF 13 PAGES
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1. NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
Keystone Investment Management Company
I.R.S. #04-1504645
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
a [X]
b [ ]
3. SEC USE ONLY
4. CITIZENSHIP OR PLACE OF ORGANIZATION
Delaware
5. SOLE VOTING POWER
479,834 Shares, Common Stock
6. SHARED VOTING POWER
None
7. SOLE DISPOSITION POWER
479,834 Shares, Common Stock
8. SHARED DISPOSITIVE POWER
None
9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
479,834 Shares, Common Stock
10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
N/A
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
10.44%
12. TYPE OF REPORTING PERSON*
CO
*SEE INSTRUCTION BEFORE FILLING OUT!
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CUSIP No. 63888210 13G PAGE 3 OF 13 PAGES
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1. NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
Keystone Small Company Growth Fund (S-4)
I.R.S. #04-2394427
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
a [X]
b [ ]
3. SEC USE ONLY
4. CITIZENSHIP OR PLACE OF ORGANIZATION
Pennsylvania
5. SOLE VOTING POWER
200,000 Shares, Common Stock
6. SHARED VOTING POWER
None
7. SOLE DISPOSITION POWER
200,000 Shares, Common Stock
8. SHARED DISPOSITIVE POWER
None
9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
200,000 Shares, Common Stock
10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
N/A
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
4.35%
12. TYPE OF REPORTING PERSON*
IV
*SEE INSTRUCTION BEFORE FILLING OUT!
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CUSIP No. 63888210 13G PAGE 4 OF 13 PAGES
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1. NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
Keystone Global Opportunities Fund
I.R.S. #04-6584551
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
a [X]
b [ ]
3. SEC USE ONLY
4. CITIZENSHIP OR PLACE OF ORGANIZATION
Massachusetts
5. SOLE VOTING POWER
65,000 Shares, Common Stock
6. SHARED VOTING POWER
None
7. SOLE DISPOSITION POWER
65,000 Shares, Common Stock
8. SHARED DISPOSITIVE POWER
None
9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
65,000 Shares, Common Stock
10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
N/A
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
1.4%
12. TYPE OF REPORTING PERSON*
IV
*SEE INSTRUCTION BEFORE FILLING OUT!
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CUSIP No. 63888210 13G PAGE 5 OF 13 PAGES
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1. NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
Keystone Small Company Growth Fund II
I.R.S. #04-3297392
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
a [X]
b [ ]
3. SEC USE ONLY
4. CITIZENSHIP OR PLACE OF ORGANIZATION
Massachusetts
5. SOLE VOTING POWER
12,100 Shares, Common Stock
6. SHARED VOTING POWER
None
7. SOLE DISPOSITION POWER
12,100 Shares, Common Stock
8. SHARED DISPOSITIVE POWER
None
9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
12,100 Shares, Common Stock
10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
N/A
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
0.26%
12. TYPE OF REPORTING PERSON*
IV
*SEE INSTRUCTION BEFORE FILLING OUT!
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CUSIP No. 63888210 13G PAGE 6 OF 13 PAGES
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1. NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
Keystone Institutional Trust - Keystone Institutional Small
Capitalization Growth Fund I.R.S. #04-3295682
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
a [X]
b [ ]
3. SEC USE ONLY
4. CITIZENSHIP OR PLACE OF ORGANIZATION
Massachusetts
5. SOLE VOTING POWER
1,700 Shares, Common Stock
6. SHARED VOTING POWER
None
7. SOLE DISPOSITION POWER
1,700 Shares, Common Stock
8. SHARED DISPOSITIVE POWER
None
9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
1,700 Shares, Common Stock
10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
N/A
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
0.04%
12. TYPE OF REPORTING PERSON*
IV
*SEE INSTRUCTION BEFORE FILLING OUT!
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CUSIP No. 63888210 13G PAGE 7 OF 13 PAGES
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1. NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
Keystone Investment Management Company
I.R.S. #04-1504645
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
a [X]
b [ ]
3. SEC USE ONLY
4. CITIZENSHIP OR PLACE OF ORGANIZATION
Delaware
5. SOLE VOTING POWER
153,434 Shares, Common Stock
6. SHARED VOTING POWER
None
7. SOLE DISPOSITION POWER
153,434 Shares, Common Stock
8. SHARED DISPOSITIVE POWER
None
9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
153,434 Shares, Common Stock
10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
N/A
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
3.34%
12. TYPE OF REPORTING PERSON*
IA (for the Merrill Lynch Consults Portfolio)**
** Total above represents aggregate holdings for approximately 2500 accounts,
managed by Keystone Investment Management Company, none of which individually
owns more than .05% of the securities.
*SEE INSTRUCTION BEFORE FILLING OUT!
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CUSIP No. 63888210 13G PAGE 8 OF 13 PAGES
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1. NAME OF REPORTING PERSON
S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
Keystone Investment Management Company
I.R.S. #04-1504645
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
a [X]
b [ ]
3. SEC USE ONLY
4. CITIZENSHIP OR PLACE OF ORGANIZATION
Delaware
5. SOLE VOTING POWER
47,600 Shares, Common Stock
6. SHARED VOTING POWER
None
7. SOLE DISPOSITION POWER
47,600 Shares, Common Stock
8. SHARED DISPOSITIVE POWER
None
9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
47,600 Shares, Common Stock
10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
N/A
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
1.04%
12. TYPE OF REPORTING PERSON*
IA (for Concord Hospital Small Capital Qualified Account
(2,400 Shares), Concord Hospital Small Capital Non-Qualified
Account (3,700), General Retirement of Detroit (23,000),
Employees Retirement System Puerto Rico Electric Power (17,000
Shares), George S. Bissell Charitable Remainder Trust (1,500))
*SEE INSTRUCTION BEFORE FILLING OUT!
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PAGE 9 OF 13 PAGES
Item 1(a). Name of Issuer:
Natural Microsystems Corp.
Item 1(b). Address of Issuer's Principal Executive Offices:
8 Erie Drive
Natick, MA 01760
Item 2(a). Name of Person Filing:
Keystone Investment Management Company
Item 2(b). Address of Principal Business Office, or, if none, residence:
200 Berkeley Street
Boston, MA 02116
Item 2(c). Place of organization:
Delaware
Item 2(d). Title of Class of Securities:
Common Stock
Item 2(e). CUSIP Number:
63888210
Item 3. If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b),
check whether the person filing is a:
(a) [ ] Broker or Dealer registered under Section 15
of the Act
(b) [ ] Bank as defined in Section 3(a)(6) of the Act
(c) [ ] Insurance Company as defined in Section
3(a)(19) of the Act
(d) [ ] Investment Company registered under Section 8
of the Investment Company Act
(e) [ ] Investment Company registered under Section
203 of the Investment Advisers Act of 1940
(f) [ ] Employee Benefit Plan, Pension Fund which is
subject to the provisions of the Employee
Retirement Income Security Act of 1974 or
Endowment Fund; see Section 240.13d-1(b)(1)(ii)(F)
(g) [ ] Parent Holding Company, in accordance with
Section 240.13d-1(b)(ii)(G) (Note: See Item 7)
(h) [X] Group, in accordance with Section 240.13d-1(b)
(1)(ii)(H)
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PAGE 10 OF 13 PAGES
Item 4. Ownership:
If the percent of the class owned, as of December 31 of the
year covered by the statement, or as of the last day of any
month described in Rule 13d-1(b)(2), if applicable, exceeds
five percent, provide the following information as of that
date and identify those shares which there is a right to
acquire.
(a) Amount Beneficially Owned:
479,834
(b) Percent of Class:
10.44%
(c) Number of shares as to which such person has:
(I) sole power to vote or to direct the vote:
479,834
(ii) shared power to vote or to direct the vote:
None
(iii) sole power to dispose or to direct the
disposition of:
479,834
(iv) shared power to dispose of or to direct the
disposition of:
None
Item 5. Ownership of Five Percent or Less of a Class:
If this statement is being filed to report the fact that as of
the date hereof the reporting person has ceased to be the
beneficial owner of more than five percent of the class of
securities, check the following [ ].
Item 6. Ownership of More than Five Percent on Behalf of Another Person:
N/A
Item 7. Identification and Classification of the Subsidiary
Which Acquired the Security Being Reported on by the Parent Holding
Company:
N/A
Item 8. Identification and Classification of Members of the Group:
See Exhibit A
Item 9. Notice of Dissolution of Group:
N/A
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PAGE 11 OF 13 PAGES
Item 10. Certification:
The following certificate shall be included if the statement
is filed pursuant to Rule 13-1(b):
By signing below I certify that, to the best of my knowledge
and belief, the securities referred to above were acquired in
the ordinary course of business and were not acquired for the
purpose of and do not have the effect of changing or
influencing the control of the issuer of such securities and
were not acquired in connection with or as a participant in
any transaction having such purposes of effect.
After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this
statement is true, complete and correct.
KEYSTONE INVESTMENT MANAGEMENT COMPANY
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(Name of Entity)
By /s/ Albert H. Elfner, III
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Title: Chairman
Dated: July 1, 1996
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PAGE 12 OF 13 PAGES
EXHIBIT A
MEMBERS OF THE GROUP (Item 8)
Item 3
Identity Classification
1. Keystone Investment Management Company (e) Investment Adviser
2. Keystone Small Company Growth Fund (S-4) (d) Investment Company
3. Keystone Global Oppportunities Fund (d) Investment Company
4. Keystone Small Company Growth Fund II (d) Investment Company
5. Keystone Institutional Trust - Keystone
Institutional Small Capitalization Fund (d) Investment Company
6. Keystone Investment Management Company (e) Investment Adviser
7. Keystone Investment Management Company (e) Investment Adviser
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PAGE 13 OF 13 PAGES
EXHIBIT B
The undersigned all hereby agree in writing that Schedule 13G, filed with the
Securities and Exchange Commission by Keystone Investment Management Company,
and containing information required by Schedule 13G with respect to beneficial
ownership of the same shares of the Common Stock of Natural Microsystems Corp.
is jointly filed on behalf of each of Keystone Investment Management Company,
Keystone Small Company Growth Fund (S-4), Keystone Global Opportunities Fund,
Keystone Small Company Growth Fund II, Keystone Institutional Trust - Keystone
Institutional Small Capitalization Fund, Keystone Investment Management Company
for Merrill Lynch Wrap Account, Keystone Investment Management Company for
Concord Hospital Small Capital Qualified Account, Concord Hospital Small Capital
Non-Qualified Account, General Retirement of Detroit, Employees Retirement
System Puerto Rico Electric Power, George S. Bissell Charitable Remainder Trust.
KEYSTONE INVESTMENT MANAGEMENT COMPANY
By: /s/ Albert H. Elfner, III
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Title: Chairman
KEYSTONE SMALL COMPANY GROWTH FUND (S-4)
By: /s/ Albert H. Elfner, III
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Title: Chairman
KEYSTONE GLOBAL OPPORTUNITIES FUND
By: /s/ Albert H. Elfner, III
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Title: Chairman
KEYSTONE SMALL COMPANY GROWTH FUND II
By: /s/ Albert H. Elfner, III
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Title: Chairman
KEYSTONE INSTITUTIONAL TRUST - KEYSTONE INSTITUTIONAL SMALL CAPITALIZATION FUND
By: /s/ Albert H. Elfner, III
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Title: Chairman
KEYSTONE INVESTMENT MANAGEMENT COMPANY for Merrill Lynch Wrap Account
By: /s/ Albert H. Elfner, III
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Title: Chairman
KEYSTONE INVESTMENT MANAGEMENT COMPANY for Concord Hospital Small Capital
Qualified Account, Concord Hospital Small Capital Non-Qualified Account, General
Retirement of Detroit, Employees Retirement System Puerto Rico Electric Power,
George S. Bissell Charitable Remainder Trust
By: /s/ Albert H. Elfner, III
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Title: Chairman
