WITTER DEAN FEDERAL SECURITIES TRUST
497, 1997-07-29
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<PAGE>
                         DEAN WITTER
                         FEDERAL SECURITIES TRUST
                         PROSPECTUS--JULY 28, 1997
 
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DEAN WITTER FEDERAL SECURITIES TRUST (THE "FUND") IS AN OPEN-END DIVERSIFIED
MANAGEMENT INVESTMENT COMPANY WHOSE INVESTMENT OBJECTIVE IS TO EARN A HIGH LEVEL
OF CURRENT INCOME. THE FUND WILL SEEK TO ACHIEVE ITS INVESTMENT OBJECTIVE BY
INVESTING PRIMARILY IN DEBT SECURITIES ISSUED BY THE U.S. GOVERNMENT, ITS
AGENCIES OR INSTRUMENTALITIES, INCLUDING MORTGAGE-BACKED SECURITIES, AND BY
WRITING COVERED CALL AND PUT OPTIONS AGAINST SUCH SECURITIES. THE FUND MAY ALSO
PURCHASE OPTIONS ON SUCH SECURITIES TO EFFECT CLOSING TRANSACTIONS. IN ADDITION,
TO HEDGE THE FUND'S PORTFOLIO OF SECURITIES AGAINST CHANGES IN PREVAILING
INTEREST RATES, THE FUND MAY PURCHASE PUT OPTIONS ON U.S. GOVERNMENT SECURITIES
AND ENGAGE IN TRANSACTIONS INVOLVING INTEREST RATE FUTURES CONTRACTS AND OPTIONS
ON SUCH CONTRACTS. SHARES OF THE FUND ARE NOT ISSUED, INSURED OR GUARANTEED, AS
TO VALUE OR YIELD, BY THE U.S. GOVERNMENT, ITS AGENCIES OR INSTRUMENTALITIES.
(SEE "INVESTMENT OBJECTIVE AND POLICIES.")
 
The Fund offers four classes of shares (each, a "Class"), each with a different
combination of sales charges, ongoing fees and other features. The different
distribution arrangements permit an investor to choose the method of purchasing
shares that the investor believes is most beneficial given the amount of the
purchase, the length of time the investor expects to hold the shares and other
relevant circumstances. Shares of the Fund held prior to July 28, 1997 have been
designated Class B shares. (See "Purchase of Fund Shares--Alternative Purchase
Arrangements.")
 
This Prospectus sets forth concisely the information you should know before
investing in the Fund. It should be read and retained for future reference.
Additional information about the Fund is contained in the Statement of
Additional Information, dated July 28, 1997, which has been filed with the
Securities and Exchange Commission, and which is available at no charge upon
request of the Fund at the address or telephone numbers listed on this page. The
Statement of Additional Information is incorporated herein by reference.
 
<TABLE>
<CAPTION>
TABLE OF CONTENTS
 
<S>                                                 <C>
Prospectus Summary................................       2
 
Summary of Fund Expenses..........................       4
 
Financial Highlights..............................       5
 
The Fund and its Management.......................       6
 
Investment Objective and Policies.................       6
 
  Risk Considerations.............................      10
 
Investment Restrictions...........................      12
 
Purchase of Fund Shares...........................      13
 
Shareholder Services..............................      21
 
Redemptions and Repurchases.......................      23
 
Dividends, Distributions and Taxes................      24
 
Performance Information...........................      25
 
Additional Information............................      25
</TABLE>
 
SHARES OF THE FUND ARE NOT DEPOSITS OR OBLIGATIONS OF, OR GUARANTEED OR ENDORSED
BY, ANY BANK, AND THE SHARES ARE NOT FEDERALLY INSURED BY THE FEDERAL DEPOSIT
INSURANCE CORPORATION, THE FEDERAL RESERVE BOARD, OR ANY OTHER AGENCY.
 
DEAN WITTER
FEDERAL SECURITIES TRUST
TWO WORLD TRADE CENTER
NEW YORK, NEW YORK 10048
(212) 392-2550 or (800) 869-NEWS (toll-free)
 
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  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
 EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
   AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
                               CRIMINAL OFFENSE.
 
                   DEAN WITTER DISTRIBUTORS INC., DISTRIBUTOR
<PAGE>
PROSPECTUS SUMMARY
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<TABLE>
<S>             <C>
THE FUND        The Fund is organized as a Trust, commonly known as a Massachusetts business trust, and
                is an open-end diversified management investment company which invests principally in
                U.S. Government securities.
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SHARES OFFERED  Shares of beneficial interest with $0.01 par value (see page 25). The Fund offers four
                Classes of shares, each with a different combination of sales charges, ongoing fees and
                other features (see pages 13-20).
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MINIMUM         The minimum initial investment for each Class is $1,000 ($100 if the account is opened
PURCHASE        through EasyInvest-SM-). Class D shares are only available to persons investing $5
                million or more and to certain other limited categories of investors. For the purpose of
                meeting the minimum $5 million investment for Class D shares, and subject to the $1,000
                minimum initial investment for each Class of the Fund, an investor's existing holdings
                of Class A shares and shares of funds for which Dean Witter InterCapital Inc. serves as
                investment manager ("Dean Witter Funds") that are sold with a front-end sales charge,
                and concurrent investments in Class D shares of the Fund and other Dean Witter Funds
                that are multiple class funds, will be aggregated. The minimum subsequent investment is
                $100 (see page 13).
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INVESTMENT      The investment objective of the Fund is to earn a high level of current income.
OBJECTIVE
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INVESTMENT      Dean Witter InterCapital Inc. ("InterCapital"), the Investment Manager of the Fund, and
MANAGER         its wholly-owned subsidiary, Dean Witter Services Company, Inc., serve in various
                investment management, advisory, management and administrative capacities to 100
                investment companies and other portfolios with assets of approximately $96.6 billion at
                June 30, 1997 (see page 6).
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MANAGEMENT      The Investment Manager receives a monthly fee at the annual rate of 0.55% of the Fund's
FEE             daily net assets not exceeding $1 billion, scaled down at various asset levels to 0.35%
                of the Fund's daily net assets on assets exceeding $12.5 billion (see page 6).
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DISTRIBUTOR     Dean Witter Distributors Inc. (the "Distributor"). The Fund has adopted a distribution
AND             plan pursuant to Rule 12b-1 under the Investment Company Act (the "12b-1 Plan") with
DISTRIBUTION    respect to the distribution fees paid by the Class A, Class B and Class C shares of the
FEE             Fund to the Distributor. The entire 12b-1 fee payable by Class A and a portion of the
                12b-1 fee payable by each of Class B and Class C equal to 0.20% of the average daily net
                assets of Class B and 0.25% of the average daily net assets of Class C are currently
                each characterized as a service fee within the meaning of the National Association of
                Securities Dealers, Inc. guidelines. The remaining portion of the 12b-1 fee, if any, is
                characterized as an asset-based sales charge (see pages 13 and 19).
- -------------------------------------------------------------------------------------------------------
ALTERNATIVE     Four classes of shares are offered:
PURCHASE
ARRANGEMENTS    - Class A shares are offered with a front-end sales charge, starting at 4.25% and
                reduced for larger purchases. Investments of $1 million or more (and investments by
                certain other limited categories of investors) are not subject to any sales charge at
                the time of purchase but a contingent deferred sales charge ("CDSC") of 1.0% may be
                imposed on redemptions within one year of purchase. The Fund is authorized to reimburse
                the Distributor for specific expenses incurred in promoting the distribution of the
                Fund's Class A shares and servicing shareholder accounts pursuant to the Fund's 12b-1
                Plan. Reimbursement may in no event exceed an amount equal to payments at an annual rate
                of 0.25% of average daily net assets of the Class (see pages 13, 16 and 19).
                - Class B shares are offered without a front-end sales charge, but will in most cases be
                subject to a CDSC (scaled down from 5.0% to 1.0%) if redeemed within six years after
                purchase. The CDSC will be imposed on any redemption of shares if after such redemption
                the aggregate current value of a Class B account with the Fund falls below the aggregate
                amount of the investor's purchase payments made during the six years preceding the
                redemption. A different CDSC schedule applies to investments by certain qualified plans.
                Class B shares are also subject to a 12b-1 fee assessed at the annual rate of 0.85% of
                the lesser of: (a) the average daily net sales of the Fund's Class B shares or (b) the
                average daily net assets of Class B. All shares of the Fund held prior to July 28, 1997
                have been designated Class B shares. Shares held before May 1, 1997 will convert to
                Class A shares in May, 2007. In all other instances, Class B shares convert to Class A
                shares approximately ten years after the date of the original purchase (see pages 13, 17
                and 19).
                - Class C shares are offered without a front-end sales charge, but will in most cases be
                subject to a CDSC of 1.0% if redeemed within one year after purchase. The Fund is
                authorized to reimburse the Distributor for specific expenses incurred in promoting the
                distribution of the Fund's Class C shares and servicing shareholder accounts pursuant to
                the Fund's 12b-1 Plan. Reimbursement may in no event exceed an amount equal to payments
                at an annual rate of 0.85% of average daily net assets of the Class (see pages 13 and
                19).
- -------------------------------------------------------------------------------------------------------
</TABLE>
 
2
<PAGE>
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<TABLE>
<S>             <C>
                - Class D shares are offered only to investors meeting an initial investment minimum of
                $5 million and to certain other limited categories of investors. Class D shares are
                offered without a front-end sales charge or CDSC and are not subject to any 12b-1 fee
                (see pages 13 and 19).
- -------------------------------------------------------------------------------------------------------
DIVIDENDS       Dividends from net investment income are declared daily and paid monthly. Capital gains
AND             distributions are paid at least annually. The Fund may, however, determine to retain all
CAPITAL GAINS   or part of any net long-term capital gains in any year for reinvestment. Dividends and
DISTRIBUTIONS   capital gains distributions paid on shares of a Class are automatically reinvested in
                additional shares of the same Class at net asset value unless the shareholder elects to
                receive cash. Shares acquired by dividend and distribution reinvestment will not be
                subject to any sales charge or CDSC (see pages 21 and 24).
- -------------------------------------------------------------------------------------------------------
REDEMPTION      Shares are redeemable by the shareholder at net asset value less any applicable CDSC on
                Class A, Class B or Class C shares. An account may be involuntarily redeemed if the
                total value of the account is less than $100 or, if the account was opened through
                EasyInvest-SM-, if after twelve months the shareholder has invested less than $1,000 in
                the account (see page 23).
- -------------------------------------------------------------------------------------------------------
SPECIAL RISK    The net asset value of the Fund's shares will fluctuate with changes in the market value
CONSIDERATIONS  of its portfolio securities. The Fund's yield will also vary based on the yield of the
                Fund's portfolio securities. The Fund may purchase and write options on debt
                instruments, in both exchange-listed and over-the-counter transactions, and engage in
                transactions involving futures contracts and options thereon. In addition, the Fund may
                borrow money and thereby leverage its securities investments (in an amount up to 25% of
                the Fund's total assets) and purchase securities on a when-issued and delayed delivery
                and firm commitment basis. These investments may involve special risks (see pages
                10-12).
- -------------------------------------------------------------------------------------------------------
</TABLE>
 
  THE ABOVE IS QUALIFIED IN ITS ENTIRETY BY THE DETAILED INFORMATION APPEARING
  ELSEWHERE IN THIS PROSPECTUS AND IN THE STATEMENT OF ADDITIONAL INFORMATION
 
                                                                               3
<PAGE>
SUMMARY OF FUND EXPENSES
- --------------------------------------------------------------------------------
 
The following table illustrates all expenses and fees that a shareholder of the
Fund will incur. The expenses and fees set forth in the table are based on the
expenses and fees for the fiscal year ended October 31, 1996.
 
<TABLE>
<CAPTION>
                                   CLASS A        CLASS B        CLASS C        CLASS D
                                  ----------     ----------     ----------     ----------
<S>                               <C>            <C>            <C>            <C>
SHAREHOLDER TRANSACTION
 EXPENSES
Maximum Sales Charge Imposed
 on Purchases (as a percentage
 of offering price)...........      4.25%(1)       None           None           None
Sales Charge Imposed on
 Dividend Reinvestments.......      None           None           None           None
Maximum Contingent Deferred
 Sales Charge (as a percentage
 of original purchase price or
 redemption proceeds).........      None(2)        5.00%(3)       1.00%(4)       None
Redemption Fees...............      None           None           None           None
Exchange Fee..................      None           None           None           None
 
ANNUAL FUND OPERATING EXPENSES
 (AS A PERCENTAGE OF AVERAGE
 NET ASSETS)
Management Fees...............      0.55%          0.55%          0.55%          0.55%
12b-1 Fees (5) (6)............      0.25%          0.85%          0.85%          None
Other Expenses................      0.13%          0.13%          0.13%          0.13%
Total Fund Operating Expenses
 (7)..........................      0.93%          1.53%          1.53%          0.68%
</TABLE>
 
- ---------------
(1) REDUCED FOR PURCHASES OF $25,000 AND OVER (SEE "PURCHASE OF FUND
    SHARES--INITIAL SALES CHARGE ALTERNATIVE--CLASS A SHARES").
(2) INVESTMENTS THAT ARE NOT SUBJECT TO ANY SALES CHARGE AT THE TIME OF PURCHASE
    ARE SUBJECT TO A CDSC OF 1.00% THAT WILL BE IMPOSED ON REDEMPTIONS MADE
    WITHIN ONE YEAR AFTER PURCHASE, EXCEPT FOR CERTAIN SPECIFIC CIRCUMSTANCES
    (SEE "PURCHASE OF FUND SHARES--INITIAL SALES CHARGE ALTERNATIVE--CLASS A
    SHARES").
(3) THE CDSC IS SCALED DOWN TO 1.00% DURING THE SIXTH YEAR, REACHING ZERO
    THEREAFTER.
(4) ONLY APPLICABLE TO REDEMPTIONS MADE WITHIN ONE YEAR AFTER PURCHASE (SEE
    "PURCHASE OF FUND SHARES--LEVEL LOAD ALTERNATIVE--CLASS C SHARES").
(5) THE 12b-1 FEE IS ACCRUED DAILY AND PAYABLE MONTHLY. THE ENTIRE 12b-1 FEE
    PAYABLE BY CLASS A AND A PORTION OF THE 12b-1 FEE PAYABLE BY EACH OF CLASS B
    AND CLASS C EQUAL TO 0.20% OF THE AVERAGE DAILY NET ASSETS OF CLASS B AND
    0.25% OF THE AVERAGE DAILY NET ASSETS OF CLASS C ARE CURRENTLY EACH
    CHARACTERIZED AS A SERVICE FEE WITHIN THE MEANING OF NATIONAL ASSOCIATION OF
    SECURITIES DEALERS, INC. ("NASD") GUIDELINES AND ARE PAYMENTS MADE FOR
    PERSONAL SERVICE AND/OR MAINTENANCE OF SHAREHOLDER ACCOUNTS. THE REMAINDER
    OF THE 12b-1 FEE, IF ANY, IS AN ASSET-BASED SALES CHARGE, AND IS A
    DISTRIBUTION FEE PAID TO THE DISTRIBUTOR TO COMPENSATE IT FOR THE SERVICES
    PROVIDED AND THE EXPENSES BORNE BY THE DISTRIBUTOR AND OTHERS IN THE
    DISTRIBUTION OF THE FUND'S SHARES (SEE "PURCHASE OF FUND SHARES--PLAN OF
    DISTRIBUTION").
(6) UPON CONVERSION OF CLASS B SHARES TO CLASS A SHARES, SUCH SHARES WILL BE
    SUBJECT TO THE LOWER 12b-1 FEE APPLICABLE TO CLASS A SHARES. NO SALES CHARGE
    IS IMPOSED AT THE TIME OF CONVERSION OF CLASS B SHARES TO CLASS A SHARES.
    CLASS C SHARES DO NOT HAVE A CONVERSION FEATURE AND, THEREFORE, ARE SUBJECT
    TO AN ONGOING 0.85% DISTRIBUTION FEE (SEE "PURCHASE OF FUND
    SHARES--ALTERNATIVE PURCHASE ARRANGEMENTS").
(7) THERE WERE NO OUTSTANDING SHARES OF CLASS A, CLASS C OR CLASS D PRIOR TO THE
    DATE OF THIS PROSPECTUS. ACCORDINGLY, "TOTAL FUND OPERATING EXPENSES," AS
    SHOWN ABOVE WITH RESPECT TO THOSE CLASSES, ARE BASED UPON THE SUM OF 12b-1
    FEES, MANAGEMENT FEES AND ESTIMATED "OTHER EXPENSES."
 
<TABLE>
<CAPTION>
EXAMPLES                                                                 1 YEAR       3 YEARS      5 YEARS     10 YEARS
                                                                       -----------  -----------  -----------  -----------
<S>                                                                    <C>          <C>          <C>          <C>
You would pay the following expenses on a $1,000 investment
 assuming(1) a 5% annual return and (2) redemption at the end of each
 time period:
    Class A..........................................................   $      52    $      71    $      92    $     152
    Class B..........................................................   $      66    $      78    $     103    $     182
    Class C..........................................................   $      26    $      48    $      83    $     182
    Class D..........................................................   $       7    $      22    $      38    $      85
 
You would pay the following expenses on the same $1,000 investment
 assuming no redemption at the end of the period:
    Class A..........................................................   $      52    $      71    $      92    $     152
    Class B..........................................................   $      16    $      48    $      83    $     182
    Class C..........................................................   $      16    $      48    $      83    $     182
    Class D..........................................................   $       7    $      22    $      38    $      85
</TABLE>
 
THE ABOVE EXAMPLES SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE
EXPENSES OR PERFORMANCE. ACTUAL EXPENSES OF EACH CLASS MAY BE GREATER OR LESS
THAN THOSE SHOWN.
 
The purpose of this table is to assist the investor in understanding the various
costs and expenses that an investor in the Fund will bear directly or
indirectly. For a more complete description of these costs and expenses, see
"The Fund and its Management," "Purchase of Fund Shares--Plan of Distribution"
and "Redemptions and Repurchases."
 
Long-term shareholders of Class B and Class C may pay more in sales charges,
including distribution fees, than the economic equivalent of the maximum
front-end sales charges permitted by the NASD.
 
4
<PAGE>
FINANCIAL HIGHLIGHTS
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The following ratios and per share data for a share of beneficial interest
outstanding throughout each of the periods through October 31, 1996 have been
audited by Price Waterhouse LLP, independent accountants. The information for
the six-month period ended April 30, 1997 is unaudited. The financial highlights
should be read in conjunction with the financial statements, notes thereto, and
the unqualified report of independent accountants, which are contained in the
Statement of Additional Information. Further information about the performance
of the Fund is contained in the Fund's Annual Report to Shareholders, which may
be obtained without charge upon request to the Fund. All shares of the Fund held
prior to July 28, 1997 have been designated Class B shares.
<TABLE>
<CAPTION>
                                                                   FOR THE YEAR ENDED OCTOBER 31
                                      ----------------------------------------------------------------------------------------
                                        1996      1995      1994      1993      1992      1991      1990      1989      1988
                                      --------  --------  --------  --------  --------  --------  --------  --------  --------
                           FOR THE
                             SIX
                            MONTHS
                            ENDED
                          APRIL 30,
                             1997
                          ----------
                          (UNAUDITED)
PER SHARE OPERATING
 PERFORMANCE:
<S>                       <C>         <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>
Net asset value,
 beginning of period..... $    9.25   $  9.49   $  8.74   $ 10.03   $  9.57   $  9.46   $  8.87   $  9.27   $  9.13   $  9.27
                          ----------  --------  --------  --------  --------  --------  --------  --------  --------  --------
  Net investment
   income................      0.29      0.59      0.59      0.60      0.65      0.68      0.72      0.72      0.71      0.74
  Net realized and
   unrealized gain
   (loss)................     (0.22)    (0.25)     0.75     (1.28)     0.46      0.11      0.59     (0.40)     0.34      0.08
                          ----------  --------  --------  --------  --------  --------  --------  --------  --------  --------
  Total from investment
   operations............      0.07      0.34      1.34    (0.68)      1.11      0.79      1.31      0.32      1.05      0.82
                          ----------  --------  --------  --------  --------  --------  --------  --------  --------  --------
  Less dividends and
   distributions from:
    Net investment
     income..............    (0.29)    (0.58)    (0.59)    (0.61)    (0.65)    (0.68)    (0.72)    (0.72)    (0.71)    (0.74)
    Net realized gain....    --         --        --        --        --        --        --        --        --        --
    Paid-in-capital......    --         --        --        --        --        --        --        --       (0.20)    (0.22)
                          ----------  --------  --------  --------  --------  --------  --------  --------  --------  --------
  Total dividends and
   distributions.........    (0.29)    (0.58)    (0.59)    (0.61)    (0.65)    (0.68)    (0.72)    (0.72)    (0.91)    (0.96)
                          ----------  --------  --------  --------  --------  --------  --------  --------  --------  --------
  Net asset value, end of
   period................ $    9.03   $  9.25   $  9.49   $  8.74   $ 10.03   $  9.57   $  9.46   $  8.87   $  9.27   $  9.13
                          ----------  --------  --------  --------  --------  --------  --------  --------  --------  --------
                          ----------  --------  --------  --------  --------  --------  --------  --------  --------  --------
TOTAL INVESTMENT
 RETURN+.................      0.79%(1)    3.79%   15.89%  (6.92)%    12.03%     8.56%    15.26%     3.64%    12.32%     9.21%
  Ratios to average net
   assets:
    Expenses.............      1.53%(2)    1.53%    1.52%    1.52%     1.50%     1.48%     1.50%     1.54%     1.47%     1.50%
    Net investment
     income..............      6.42%(2)    6.31%    6.53%    6.56%     6.59%     7.18%     7.79%     7.92%     7.90%     8.04%
SUPPLEMENTAL DATA:
  Net assets, end of
   period, in millions...      $637      $720      $829      $841    $1,128    $1,171    $1,252    $1,397    $1,824    $2,122
  Portfolio turnover
   rate..................         6%(1)      10%       7%      18%        7%        6%       --%++       5%      19%       44%
 
<CAPTION>
                              FOR THE PERIOD
                             MARCH 31, 1987*
                                 THROUGH
                             OCTOBER 31, 1987
                          ----------------------
 
PER SHARE OPERATING
 PERFORMANCE:
<S>                       <C>
Net asset value,
 beginning of period..... $               10.00
                                         ------
  Net investment
   income................                  0.43
  Net realized and
   unrealized gain
   (loss)................                 (0.58)
                                         ------
  Total from investment
   operations............                (0.15)
                                         ------
  Less dividends and
   distributions from:
    Net investment
     income..............                (0.43)
    Net realized gain....                (0.15)
    Paid-in-capital......          --
                                         ------
  Total dividends and
   distributions.........                (0.58)
                                         ------
  Net asset value, end of
   period................ $                9.27
                                         ------
                                         ------
TOTAL INVESTMENT
 RETURN+.................                (1.47)%(1)
  Ratios to average net
   assets:
    Expenses.............                  1.54%(2)
    Net investment
     income..............                  7.76%(2)
SUPPLEMENTAL DATA:
  Net assets, end of
   period, in millions...                $2,067
  Portfolio turnover
   rate..................                    32%(1)
</TABLE>
 
- ------------
 *  COMMENCEMENT OF OPERATIONS.
 +  DOES NOT REFLECT THE DEDUCTION OF SALES CHARGE. CALCULATED BASED ON THE NET
    ASSET VALUE AS OF THE LAST BUSINESS DAY OF THE PERIOD.
 ++  LESS THAN 0.5%.
(1) NOT ANNUALIZED.
(2) ANNUALIZED.
 
                                                                               5
<PAGE>
THE FUND AND ITS MANAGEMENT
- --------------------------------------------------------------------------------
 
Dean Witter Federal Securities Trust (the "Fund") is an open-end diversified
management investment company. The Fund is a trust of the type commonly known as
a "Massachusetts business trust" and was organized under the laws of
Massachusetts on November 20, 1986.
 
    Dean Witter InterCapital Inc. ("InterCapital" or the "Investment Manager"),
whose address is Two World Trade Center, New York, New York 10048, is the Fund's
Investment Manager. The Investment Manager, which was incorporated in July,
1992, is a wholly-owned subsidiary of Morgan Stanley, Dean Witter, Discover &
Co., a preeminent global financial services firm that maintains leading market
positions in each of its three primary businesses -- securities, asset
management and credit services.
 
    InterCapital and its wholly-owned subsidiary, Dean Witter Services Company
Inc., serve in various investment management, advisory, management and
administrative capacities to 100 investment companies, thirty of which are
listed on the New York Stock Exchange, with combined total assets of
approximately $93.1 billion at June 30, 1997. The Investment Manager also
manages portfolios of pension plans, other institutions and individuals which
aggregated approximately $3.5 billion at such date.
 
    The Fund has retained the Investment Manager to provide administrative
services, manage its business affairs and manage the investment of the Fund's
assets, including the placing of orders for the purchase and sale of portfolio
securities. InterCapital has retained Dean Witter Services Company Inc. to
perform the aforementioned administrative services for the Fund.
 
    The Fund's Trustees review the various services provided by or under the
direction of the Investment Manager to ensure that the Fund's general investment
policies and programs are being properly carried out and that administrative
services are being provided to the Fund in a satisfactory manner.
 
    As full compensation for the services and facilities furnished to the Fund
and for expenses of the Fund assumed by the Investment Manager, the Fund pays
the Investment Manager monthly compensation calculated daily by applying the
following annual rates to the Fund's net assets determined as of the close of
each business day: 0.55% of the portion of the Fund's daily net assets not
exceeding $1 billion, scaled down at various asset levels to 0.35% of the
portion of daily net assets exceeding $12.5 billion. For the fiscal year ended
October 31, 1996, the Fund accrued total compensation to the Investment Manager
amounting to 0.55% of the Fund's average daily net assets and the Fund's total
expenses amounted to 1.53% of the Fund's average daily net assets.
 
INVESTMENT OBJECTIVE AND POLICIES
- --------------------------------------------------------------------------------
 
The investment objective of the Fund is to earn a high level of current income.
There can be no assurance that the investment objective will be achieved. This
objective is fundamental and cannot be changed without shareholder approval. The
following policies may be changed by the Board of Trustees without shareholder
approval.
 
    The Fund will seek to achieve its objective primarily by investing at least
65% of its total assets in U.S. Government securities (including such securities
purchased on a when-issued, delayed delivery or firm commitment basis). U.S.
Government securities include:
 
        (1) U.S. Treasury bills (maturities of one year or less), U.S. Treasury
    notes (maturities of one to ten years) and U.S. Treasury bonds (generally
    maturities of greater than ten years), all of which are direct obligations
    of the U.S. Government and, as such, are backed by the "full faith and
    credit" of the United States.
 
        (2) Securities issued by agencies and instrumentalities of the U.S.
    Government which are backed by the full faith and credit of the United
    States. Among the agencies and instrumentalities issuing such obligations
    are the Federal Housing Administration, the Government National Mortgage
    Association ("GNMA"), the Department of Housing and Urban Development, the
    Export-Import Bank, the Farmers Home Administration, the General Services
    Administration, the Maritime Administration and the Small Business
    Administration. The maturities of such obligations range from three months
    to thirty years.
 
        (3) Securities issued by agencies and instrumentalities which are not
    backed by the full faith and credit of the United States, but whose issuing
    agency or instrumentality has the right to borrow, to meet its obligations,
    from an existing line of credit with the U.S. Treasury. Among the agencies
    and instrumentalities issuing such obligations are the Tennessee Valley
    Authority, the Federal National Mortgage Association ("FNMA"), the Federal
    Home Loan Mortgage Corporation ("FHLMC") and the U.S. Postal Service.
 
        (4) Securities issued by agencies and instrumentalities which are not
    backed by the full faith and credit of the United States, but which are
    backed by the credit of the issuing agency or instrumentality. Among the
    agencies and instrumentalities issuing such obligations are the Federal Farm
    Credit System and the Federal Home Loan Banks.
 
    The Fund is not limited as to the maturities of the U.S. Government
securities in which it may invest. For a
 
6
<PAGE>
discussion of the risks of investing in such securities (including such
securities purchased on a when-issued, delayed delivery or firm commitment basis
and zero coupon securities), see "Risk Considerations" below.
 
MORTGAGE-BACKED SECURITIES.  The Fund may invest in fixed-rate and adjustable
rate U.S. mortgage-backed securities ("Mortgage-Backed Securities"). There are
currently three basic types of U.S. Mortgage-Backed Securities: (i) those issued
or guaranteed by the U.S. Government or one of its agencies or
instrumentalities, such as GNMA, FNMA and FHLMC (securities issued by GNMA, but
not those issued by FNMA or FHLMC, are backed by the "full faith and credit" of
the United States); (ii) those issued by private issuers that represent an
interest in or are collateralized by Mortgage-Backed Securities issued or
guaranteed by the U.S. Government or one of its agencies or instrumentalities;
and (iii) those issued by private issuers that represent an interest in or are
collateralized by whole mortgage loans or Mortgage-Backed Securities without a
government guarantee but usually having some form of private credit enhancement.
 
    The Fund will invest in mortgage pass-through securities representing
participation interests in pools of residential mortgage loans originated by
U.S. governmental or private lenders such as banks, broker-dealers and financing
corporations and guaranteed, to the extent provided in such securities, by the
U.S. Government or one of its agencies or instrumentalities. Such securities,
which are ownership interests in the underlying mortgage loans, differ from
conventional debt securities, which provide for periodic payment of interest in
fixed amounts (usually semi-annually) and principal payments at maturity or on
specified call dates. Mortgage pass-through securities provide for monthly
payments that are a "pass-through" of the monthly interest and principal
payments (including any prepayments) made by the individual borrowers on the
pooled mortgage loans, net of any fees paid to the guarantor of such securities
and the servicer of the underlying mortgage loans.
 
    The guaranteed mortgage pass-through securities in which the Fund may invest
include those issued or guaranteed by GNMA, FNMA and FHLMC. GNMA certificates
are direct obligations of the U.S. Government and, as such, are backed by the
"full faith and credit" of the United States. FNMA and FHLMC certificates are
not backed by the full faith and credit of the United States but, as noted
above, the issuing agency or instrumentality has the right to borrow, to meet
its obligations, from an existing line of credit with the U.S. Treasury. The
U.S. Treasury has no legal obligation to provide such line of credit and may
choose not to do so.
 
    Certificates for Mortgage-Backed Securities evidence an interest in a
specific pool of mortgages. These certificates are, in most cases, "modified
pass-through" instruments, wherein the issuing agency guarantees the payment of
principal and interest on mortgages underlying the certificates, whether or not
such amounts are collected by the issuer on the underlying mortgages.
 
ADJUSTABLE RATE MORTGAGE SECURITIES.  The Fund may also invest in adjustable
rate mortgage securities ("ARMs"), which are pass-through mortgage securities
collateralized by mortgages with adjustable rather than fixed rates. ARMs
eligible for inclusion in a mortgage pool generally provide for a fixed initial
mortgage interest rate for either the first three, six, twelve or thirteen
scheduled monthly payments. Thereafter, the interest rates are subject to
periodic adjustment based on changes to a designated benchmark index.
 
    ARMs contain maximum and minimum rates beyond which the mortgage interest
rate may not vary over the lifetime of the security. In addition, certain ARMs
provide for additional limitations on the maximum amount by which the mortgage
interest rate may adjust for any single adjustment period. Alternatively,
certain ARMs contain limitations on changes in the required monthly payment. In
the event that a monthly payment is not sufficient to pay the interest accruing
on an ARM, any such excess interest is added to the principal balance of the
mortgage loan, which is repaid through future monthly payments. If the monthly
payment for such an instrument exceeds the sum of the interest accrued at the
applicable mortgage interest rate and the principal payment required at such
point to amortize the outstanding principal balance over the remaining term of
the loan, the excess is utilized to reduce the then outstanding principal
balance of the ARM.
 
PRIVATE MORTGAGE PASS-THROUGH SECURITIES.  The Fund may invest in private
mortgage pass-through securities, which are structured similarly to the GNMA,
FNMA and FHLMC mortgage pass-through securities and are issued by originators of
and investors in mortgage loans, including savings and loan associations,
mortgage banks, commercial banks, investment banks and special purpose
subsidiaries of the foregoing. These securities usually are backed by a pool of
conventional fixed rate or adjustable rate mortgage loans. Since private
mortgage pass-through securities typically are not guaranteed by an entity
having the credit status of GNMA, FNMA and FHLMC, such securities generally are
structured with one or more types of credit enhancement.
 
COLLATERALIZED MORTGAGE OBLIGATIONS AND MULTICLASS PASS-THROUGH SECURITIES.  The
Fund may invest in collateralized mortgage obligations or "CMOs," which are debt
obligations collateralized by mortgage loans or mortgage pass-through
securities. Typically, CMOs are collateralized by GNMA, FNMA or FHLMC
certificates, but also may be collateralized by whole loans or private mortgage
pass-through securities (such collateral collectively hereinafter referred to as
"Mortgage Assets"). Multiclass pass-through securities are equity interests in a
trust composed of Mortgage Assets. Payments of principal of and interest on the
Mortgage Assets, and any reinvestment income thereon, provide the funds to pay
debt service on the CMOs or make scheduled distributions on the multiclass pass-
through securities. CMOs may be issued by agencies or
 
                                                                               7
<PAGE>
instrumentalities of the U.S. government, or by private originators of, or
investors in, mortgage loans, including savings and loan associations, mortgage
banks, commercial banks, investment banks and special purpose subsidiaries of
the foregoing. The issuer of a series of CMOs may elect to be treated as a Real
Estate Mortgage Investment Conduit ("REMIC"). REMICs include governmental and/or
private entities that issue a fixed pool of mortgages secured by an interest in
real property. REMICs are similar to CMOs in that they issue multiple classes of
securities but, unlike CMOs, which are required to be structured as debt
securities, REMICs may be structured as indirect ownership interests in the
underlying assets of the REMICs themselves. However, there are no effects on the
Fund from investing in CMOs issued by entities that have elected to be treated
as REMICs, and all future references to CMOs shall also be deemed to include
REMICs. In addition, in reliance upon an interpretation by the staff of the
Securities and Exchange Commission, the Fund may invest without limitation in
CMOs and other Mortgage-Backed Securities which are not by definition excluded
from the provisions of the Act, and which have obtained exemptive orders from
such provisions from the Securities and Exchange Commission.
 
    In a CMO, a series of bonds or certificates is issued in multiple classes.
Each class of CMOs, often referred to as a "tranche," is issued at a specific
fixed or floating coupon rate and has a stated maturity or final distribution
date. Principal prepayments on the Mortgage Assets may cause the CMOs to be
retired substantially earlier than their stated maturities or final distribution
dates. Interest is paid or accrues on all classes of the CMOs on a monthly,
quarterly or semi-annual basis. Certain CMOs may have variable or floating
interest rates and others may be stripped (securities which provide only the
principal or interest feature of the underlying security).
 
    The principal of and interest on the Mortgage Assets may be allocated among
the several classes of a CMO series in a number of different ways. Generally,
the purpose of the allocation of the cash flow of a CMO to the various classes
is to obtain a more predictable cash flow to the individual tranches than exists
with the underlying collateral of the CMO. As a general rule, the more
predictable the cash flow is on a CMO tranche, the lower the anticipated yield
will be on that tranche at the time of issuance relative to prevailing market
yields on Mortgage-Backed Securities. As part of the process of creating more
predictable cash flows on most of the tranches in a series of CMOs, one or more
tranches generally must be created that absorb most of the volatility in the
cash flows on the underlying mortgage loans. The yields on these tranches are
generally higher than prevailing market yields on Mortgage-Backed Securities
with similar maturities. As a result of the uncertainty of the cash flows of
these tranches, the market prices of and yield on these tranches generally are
more volatile.
 
    The Fund also may invest in, among other things, parallel pay CMOs and
Planned Amortization Class CMOs ("PAC Bonds"). Parallel pay CMOs are structured
to provide payments of principal on each payment date to more than one class.
These simultaneous payments are taken into account in calculating the stated
maturity date or final distribution date of each class which, as with other CMO
structures, must be retired by its stated maturity date or final distribution
date but may be retired earlier. PAC Bonds generally require payments of a
specified amount of principal on each payment date. PAC Bonds always are
parallel pay CMOs with the required principal payment on such securities having
the highest priority after interest has been paid to all classes.
 
TYPES OF CREDIT ENHANCEMENT.  Mortgage-Backed Securities are often backed by a
pool of assets representing the obligations of a number of different parties. To
lessen the effect of failures by obligors on underlying assets to make payments,
those securities may contain elements of credit support, which fall into two
categories: (i) liquidity protection and (ii) protection against losses
resulting from ultimate default by an obligor on the underlying assets.
Liquidity protection refers to the provision of advances, generally by the
entity administering the pool of assets, to ensure that the receipt of payments
on the underlying pool occurs in a timely fashion. Protection against losses
resulting from default ensures ultimate payment of the obligations on at least a
portion of the assets in the pool. This protection may be provided through
guarantees, insurance policies or letters of credit obtained by the issuer or
sponsor from third parties, through various means of structuring the transaction
or through a combination of such approaches. The degree of credit support
provided for each issue is generally based on historical information respecting
the level of credit risk associated with the underlying assets. Delinquencies or
losses in excess of those anticipated could adversely affect the return on an
investment in a security. The Fund will not pay any fees for credit support,
although the existence of credit support may increase the price of a security.
 
    For a discussion of the risks of investing in Mortgage-Backed Securities,
see "Risk Considerations" below.
 
    To hedge against adverse changes in the prices of securities it anticipates
purchasing for its portfolio, the Fund may also write covered call and put
options against U.S. Government securities and cash held in its portfolio and
purchase options of the same or similar series to effect closing transactions.
In addition, the Fund may hedge portions of its portfolio securities against
potential changes in prevailing interest rates by purchasing put options on U.S.
Government securities and engaging in transactions involving interest rate
futures contracts and options on such contracts. See "Options and Futures
Transactions" below.
 
    While the Fund will be investing primarily in U.S. Government securities, it
may invest up to 35% of its total assets in options on U.S. Government
securities; options on futures contracts and futures contracts; repurchase
 
8
<PAGE>
agreements; reverse repurchase agreements and dollar rolls (see "Risk
Considerations" below); money market instruments, including commercial paper
rated within the two highest grades by Standard & Poor's Corporation ("S&P") or
the highest grade by Moody's Investors Service, Inc. ("Moody's"), or, if not
rated, issued by a company having an outstanding debt issue rated at least AA by
S&P or Aa by Moody's); certificates of deposit; bankers' acceptances and other
obligations of domestic banks or domestic branches of foreign banks, in each
case having total assets of at least $500 million; and obligations of foreign
governments or their respective instrumentalities or agencies. Moreover, and
notwithstanding any of the above, the Fund may invest in such instruments
without limitation, on a temporary basis, when market conditions dictate a
"defensive" investment strategy. The Fund may also borrow money for the purpose
of leveraging its investments and lend its portfolio securities, as discussed
under "Risk Considerations" below.
 
OPTIONS AND FUTURES TRANSACTIONS
 
OPTIONS.  The Fund is permitted to enter into call and put options on U.S.
Treasury notes, bonds and bills which are listed on Exchanges and written in
over-the-counter transactions ("OTC options"). Listed options are issued by the
Options Clearing Corporation ("OCC"). Ownership of a listed call option gives
the Fund the right to buy from the OCC the underlying security covered by the
option at the stated exercise price (the price per unit of the underlying
security) by filing an exercise notice prior to the expiration date of the
option. The writer (seller) of the option would then have the obligation to sell
to the OCC the underlying security at that exercise price prior to the
expiration date of the option, regardless of its then current market price.
Ownership of a listed put option would give the Fund the right to sell the
underlying security to the OCC at the stated exercise price.
 
OTC OPTIONS.  OTC options are purchased from or sold (written) to dealers or
financial institutions which have entered into direct agreements with the Fund.
With OTC options, such variables as expiration date, exercise price and premium
will be agreed upon between the Fund and the transacting dealer, without the
intermediation of a third party such as the OCC. The Fund will engage in OTC
option transactions only with member banks of the Federal Reserve System or
primary U.S. Government securities dealers or with affiliates of such banks or
dealers which have capital of at least $50 million or whose obligations are
guaranteed by an entity having capital of at least $50 million.
 
COVERED CALL WRITING.  The Fund is permitted to write covered call options on
U.S. Government securities only, without limit, in order to aid it in achieving
its investment objective. As a writer of a call option, the Fund has the
obligation, upon notice of exercise of the option, to deliver the security
underlying the option (certain listed call options written by the Fund will be
exercisable by the purchaser only on a specific date). See "Options and Futures
Transactions--Covered Call Writing" in the Statement of Additional Information.
 
COVERED PUT WRITING.  As a writer of covered put options, the Fund incurs an
obligation to buy the security underlying the option from the purchaser of the
put at the option's exercise price at any time during the option period. The
Fund will write put options for two purposes: (1) to receive the premiums paid
by purchasers; and (2) when the Investment Manager wishes to purchase the
security underlying the option at a price lower than its current market price,
in which case it will write the covered put at an exercise price reflecting the
lower purchase price sought. The aggregate value of the obligations underlying
the puts determined as of the date the options are sold will not exceed 50% of
the Fund's net assets. See "Options and Futures Transactions--Covered Put
Writing" in the Statement of Additional Information.
 
PURCHASING CALL AND PUT OPTIONS.  The Fund may invest up to 10% of its total
assets in the purchase of put and call options on U.S. Government securities.
The Fund may purchase call options only in order to close out a covered call
position. The Fund may purchase put options on U.S. Government securities which
it holds (or has the right to acquire) in its portfolio only to protect itself
against a decline in the value of the security. The Fund may also purchase put
options to close out written put positions in a manner similar to call option
closing purchase transactions. There are no other limits on the Fund's ability
to purchase call and put options.
 
FUTURES CONTRACTS.  The Fund may also purchase and sell interest rate futures
contracts ("futures contracts") that are traded on U.S. commodity exchanges on
such underlying securities as U.S. Treasury bonds, notes and bills and GNMA
certificates. As a futures contract purchaser, the Fund incurs an obligation to
take delivery of a specified amount of the obligation underlying the contract at
a specified time in the future for a specified price. As a seller of a futures
contract, the Fund incurs an obligation to deliver the specified amount of the
underlying obligation at a specified time in return for an agreed upon price.
The Fund will purchase or sell futures contracts only for the purpose of hedging
its portfolio (or anticipated portfolio) securities against changes in
prevailing interest rates. The Fund may also purchase and write call and put
options on futures contracts which are traded on an Exchange and enter into
closing transactions with respect to such options to terminate an existing
position. See "Options and Futures Transactions--Futures Contracts" and "Options
on Futures Contracts" in the Statement of Additional Information.
 
    For a discussion of the risks of options and futures transactions, see "Risk
Considerations" below and "Options and Futures Transactions" in the Statement of
Additional Information.
 
                                                                               9
<PAGE>
RISK CONSIDERATIONS
 
The net asset value of the Fund's shares will fluctuate with changes in the
market value of its portfolio securities. The Fund's yield will also vary based
on the yield of the Fund's portfolio securities. Neither the value nor the yield
of the U.S. Government securities invested in by the Fund (or the value or yield
of the shares of the Fund) is guaranteed by the U.S. Government. Such values and
yield will fluctuate with changes in prevailing interest rates and other
factors.
 
    Generally, as prevailing interest rates rise, the value of the U.S.
Government securities held by the Fund, and, concomitantly, the net asset value
of the Fund's shares, will fall. Such securities with longer maturities
generally tend to produce higher yields and are subject to greater market
fluctuation as a result of changes in interest rates than debt securities with
shorter maturities. As noted above, the Fund is not limited as to the maturities
of the U.S. Government securities in which it may invest.
 
RISKS OF MORTGAGE-BACKED SECURITIES.  Mortgage-Backed Securities have certain
different characteristics than traditional debt securities. Among the major
differences are that interest and principal payments are made more frequently,
usually monthly, and that principal may be prepaid at any time because the
underlying mortgage loans or other assets generally may be prepaid at any time.
As a result, if the Fund purchases such a security at a premium, a prepayment
rate that is faster than expected may reduce yield to maturity, while a
prepayment rate that is slower than expected may have the opposite effect of
increasing yield to maturity. Alternatively, if the Fund purchases these
securities at a discount, faster than expected prepayments will increase, while
slower than expected prepayments may reduce, yield to maturity.
 
    Mortgage-Backed Securities, like all fixed-income securities, generally
decrease in value as a result of increases in interest rates. In addition,
although generally the value of fixed-income securities increases during periods
of falling interest rates, Mortgage-Backed Securities may benefit less than
other fixed-income securities from declining interest rates because of the risk
of prepayments.
 
    The average life of Mortgage-Backed Securities varies with the maturities of
the underlying mortgage instruments, which may be up to thirty years but which
may include mortgage instruments with maturities of fifteen years, adjustable
rate mortgage instruments, variable rate mortgage instruments, graduated rate
mortgage instruments and/or other types of mortgage instruments. The assumed
average life of mortgages backing the majority of GNMA and FNMA certificates is
twelve years, and of FHLMC certificates is ten years. This average life is
likely to be substantially shorter than the original maturity of the mortgage
pools underlying the certificates, as a pool's duration may be shortened by
unscheduled or early payments of principal on the underlying mortgages. As
prepayment rates vary widely, it is not possible to accurately predict the
average life of a particular pool.
 
    Although the extent of prepayments on a pool of mortgage loans depends on
various factors, including the prevailing level of interest rates, general
economic conditions, the location and age of the mortgage and other social and
demographic conditions, as a general rule prepayments on fixed rate mortgage
loans will increase during a period of falling interest rates and decrease
during a period of rising interest rates. If the Fund has purchased securities
backed by pools containing mortgages whose yields exceed the prevailing interest
rate, any premium paid for such securities may be lost. As a result, the net
asset value of shares of the Fund and the Fund's ability to achieve its
investment objective may be adversely affected by mortgage prepayments. Amounts
available for reinvestment by the Fund are likely to be greater during a period
of declining interest rates and, as a result, likely to be reinvested at lower
interest rates than during a period of rising interest rates.
 
    There are certain risks associated specifically with CMOs. CMOs issued by
private entities are not U.S. Government securities and are not guaranteed by
any government agency, although the securities underlying a CMO may be subject
to a guarantee. Therefore, if the collateral securing the CMO, as well as any
third party credit support or guarantees, is insufficient to make payment, the
holder could sustain a loss. However, the Fund will invest in CMOs issued by
private entities only if the CMOs are rated Aaa by Moody's or AAA by S&P, or, if
unrated, such CMOs are determined to be of comparable quality to the permitted
rated investments. Also, a number of different factors, including the extent of
prepayment of principal of the Mortgage Assets, affect the availability of cash
for principal payments by the CMO issuer on any payment date and, accordingly,
affect the timing of principal payments on each CMO class.
 
RISKS OF OPTIONS AND FUTURES TRANSACTIONS.  The Fund may close out its position
as writer of an option only if a liquid secondary market exists for options of
that series. There is no assurance that such a market will exist, particularly
in the case of OTC options, as such options will generally only be closed out by
entering into a closing purchase transaction with the purchasing dealer. Also,
Exchanges may limit the amount by which the price of a futures contract may move
on any day. If the price moves equal the daily limit on successive days, then it
may prove impossible to liquidate a futures position until the daily limit moves
have ceased.
 
    The extent to which the Fund may enter into transactions involving options
and futures contracts may be limited by the Internal Revenue Code's requirements
for qualification as a regulated investment company and the Fund's intention to
qualify as such. See "Dividends, Distributions and Taxes."
 
    While the futures contracts and options transactions to be engaged in by the
Fund for the purpose of hedging the
 
10
<PAGE>
Fund's portfolio securities are not speculative in nature, there are risks
inherent in the use of such instruments. One such risk is that the Investment
Manager could be incorrect in its expectations as to the direction or extent of
various interest rate movements or the time span within which the movements take
place. For example, if the Fund sold futures contracts for the sale of
securities in anticipation of an increase in interest rates, and then interest
rates went down instead, causing bond prices to rise, the Fund would lose money
on the sale. Another risk which may arise in employing futures contracts to
protect against the price volatility of portfolio securities is that the prices
of securities subject to futures contracts (and thereby the futures contract
prices) may correlate imperfectly with the behavior of the cash prices of the
Fund's portfolio securities. See the Statement of Additional Information for
further discussion of such risks.
 
REPURCHASE AGREEMENTS.  The Fund may enter into repurchase agreements, which may
be viewed as a type of secured lending by the Fund, and which typically involve
the acquisition by the Fund of debt securities from a selling financial
institution such as a bank, savings and loan association or broker-dealer. The
agreement provides that the Fund will sell back to the institution, and that the
institution will repurchase, the underlying security at a specified price and at
a fixed time in the future, usually not more than seven days from the date of
purchase. While repurchase agreements involve certain risks not associated with
direct investments in debt securities, including the risks of default or
bankruptcy of the selling financial institution, the Fund follows procedures
designed to minimize those risks. These procedures include effecting repurchase
transactions only with large, well-capitalized and well-established financial
institutions whose financial condition will be continually monitored by the
Investment Manager subject to procedures established by the Board of Trustees of
the Fund. In addition, the value of the collateral underlying the repurchase
agreement will be at least equal to the repurchase price, including any accrued
interest earned on the repurchase agreement. In the event of a default or
bankruptcy by a selling financial institution, the Fund will seek to liquidate
such collateral. However, the exercising of the Fund's right to liquidate such
collateral could involve certain costs or delays and, to the extent that
proceeds from any sale upon a default of the obligation to repurchase were less
than the repurchase price, the Fund could suffer a loss. The Fund may not invest
in repurchase agreements that do not mature within seven days if any such
investment, together with any other illiquid assets held by the Fund, amounts to
more than 10% of its total assets.
 
LEVERAGING.  The Fund may borrow money, but only from a bank and in an amount up
to 25% of the Fund's total assets taken at the lower of market value or cost,
not including the amount borrowed. When the Fund borrows it will be because it
seeks additional income by leveraging its investments through purchasing
securities with the borrowed funds. The Fund will be required to maintain an
asset coverage (including the proceeds of borrowings) of at least 300% of such
borrowings in accordance with the provisions of the Investment Company Act of
1940, as amended (the "Act"). The investment policy provides that the Fund may
not purchase or sell a security on margin. Borrowings for leveraging will be
subject to current margin requirements of the Federal Reserve Board and where
necessary the Fund may use any or all of its securities as collateral for such
borrowings. Any investment gains made with the additional monies in excess of
interest paid will cause the net asset value of the Fund's shares to rise to a
greater extent than would otherwise be the case. Conversely, if the investment
performance of the additional monies fails to cover their cost to the Fund, net
asset value will decrease to a greater extent than would otherwise be the case.
This is the speculative factor involved in leverage. If, due to market
fluctuations or other reasons, the value of the Fund's assets (including the
proceeds of borrowings) becomes at any time less than three times the amount of
any outstanding bank debt, the Fund, within three business days, will reduce its
bank debt to the extent necessary to meet the required 300% asset coverage. In
doing this, the Fund may have to sell a portion of its investments at a time
when it may be disadvantageous to do so.
 
ZERO COUPON SECURITIES.  A portion of the fixed-income securities purchased by
the Fund may be zero coupon securities. Such securities are purchased at a
discount from their face amount, giving the purchaser the right to receive their
full value at maturity. The interest earned on such securities is, implicitly,
automatically compounded and paid out at maturity. While such compounding at a
constant rate eliminates the risk of receiving lower yields upon reinvestment of
interest if prevailing interest rates decline, the owner of a zero coupon
security will be unable to participate in higher yields upon reinvestment of
interest received on interest-paying securities if prevailing interest rates
rise.
 
    A zero coupon security pays no interest to its holder during its life.
Therefore, to the extent the Fund invests in zero coupon securities, it will not
receive current cash available for distribution to shareholders. In addition,
zero coupon securities are subject to substantially greater price fluctuations
during periods of changing prevailing interest rates than are comparable
securities which pay interest on a current basis. Current federal tax law
requires that a holder (such as the Fund) of a zero coupon security accrue a
portion of the discount at which the security was purchased as income each year
even though the Fund receives no interest payments in cash on the security
during the year.
 
WHEN-ISSUED AND DELAYED DELIVERY SECURITIES AND FIRM COMMITMENTS.  From time to
time, in the ordinary course of business, the Fund may purchase U.S. Government
securities on a when-issued or delayed delivery basis or may purchase or sell
U.S. Government securities on a firm commitment basis. When such transactions
are negotiated, the price is fixed at the time of the commitment, but delivery
and payment can take place a month or more after the
 
                                                                              11
<PAGE>
date of the commitment. There is no overall limit on the percentage of the
Fund's assets which may be committed to the purchase of securities on a
when-issued, delayed delivery or forward commitment basis. An increase in the
percentage of the Fund's assets committed to the purchase of securities on a
when-issued, delayed delivery or forward commitment basis may increase the
volatility of the Fund's net asset value.
 
REVERSE REPURCHASE AGREEMENTS AND DOLLAR ROLLS.  The Fund may also use reverse
repurchase agreements and dollar rolls as part of its investment strategy.
Reverse repurchase agreements involve sales by the Fund of portfolio assets
concurrently with an agreement by the Fund to repurchase the same assets at a
later date at a fixed price. The Fund may enter into dollar rolls in which the
Fund sells securities for delivery in the current month and simultaneously
contracts to repurchase substantially similar (same type and coupon) securities
on a specified future date. Reverse repurchase agreements and dollar rolls
involve the risk that the market value of the securities the Fund is obligated
to repurchase under the agreement may decline below the repurchase price. In the
event the buyer of securities under a reverse repurchase agreement or dollar
roll files for bankruptcy or becomes insolvent, the Fund's use of the proceeds
of the agreement may be restricted pending a determination by the other party,
or its trustee or receiver, whether to enforce the Fund's obligation to
repurchase the securities.
 
    Reverse repurchase agreements and dollar rolls are speculative techniques
involving leverage, and are considered borrowings by the Fund.
 
LENDING OF PORTFOLIO SECURITIES.  Consistent with applicable regulatory
requirements, the Fund may lend its portfolio securities to brokers, dealers and
other financial institutions, provided that such loans are callable at any time
by the Fund (subject to certain notice provisions described in the Statement of
Additional Information), and are at all times secured by cash or money market
instruments, which are maintained in a segregated account pursuant to applicable
regulations and that are equal to at least the market value, determined daily,
of the loaned securities. As with any extensions of credit, there are risks of
delay in recovery and in some cases even loss of rights in the collateral should
the borrower of the securities fail financially. However, loans of portfolio
securities will only be made to firms deemed by the Investment Manager to be
creditworthy and when the income which can be earned from such loans justifies
the attendant risks.
 
    For additional risk disclosure, please refer to the discussion of specific
investments under the "Investment Objective and Policies" section of the
Prospectus and the "Investment Practices and Policies" section of the Statement
of Additional Information.
 
PORTFOLIO MANAGEMENT
 
The Fund's portfolio is actively managed by its Investment Manager with a view
to achieving the Fund's investment objective. In determining which securities to
purchase for the Fund or hold in the Fund's portfolio, the Investment Manager
will rely on information from various sources, including research, analysis and
appraisals of brokers and dealers, including Dean Witter Reynolds Inc. ("DWR")
and other broker-dealer affiliates of InterCapital, and others regarding
economic developments and interest rate trends, and the Investment Manager's own
analysis of factors it deems relevant. The Fund is managed within InterCapital's
Taxable Fixed-Income Group, which manages twenty-four funds and fund portfolios,
with approximately $12.8 billion in assets at June 30, 1997. Rajesh K. Gupta,
Senior Vice President of InterCapital and a member of InterCapital's Taxable
Fixed-Income Group, has been the primary portfolio manager of the Fund since
June, 1987 and has been managing portfolios comprised of government securities
at InterCapital for over five years.
 
    Brokerage commissions are not normally charged on the purchase or sale of
U.S. Government obligations, but such transactions may involve costs in the form
of spreads between bid and asked prices. Orders for transactions in other
portfolio securities and commodities are placed for the Fund with a number of
brokers and dealers, including DWR and other brokers and dealers that are
affiliates of the Investment Manager. The Fund may incur brokerage commissions
on transactions conducted through such affiliates. Pursuant to an order of the
Securities and Exchange Commission, the Fund may effect principal transactions
in certain money market instruments with DWR. It is not anticipated that the
portfolio trading engaged in by the Fund will result in its portfolio turnover
rate exceeding 100%.
 
    Except as specified, the investment policies noted above are not fundamental
policies and may be changed without shareholder approval.
 
INVESTMENT RESTRICTIONS
- --------------------------------------------------------------------------------
 
The investment restrictions listed below are among the restrictions that have
been adopted by the Fund as fundamental policies. Under the Act, a fundamental
policy may not be changed without the vote of a majority of the outstanding
voting securities of the Fund, as defined in the Act.
 
    The Fund may not:
        1. Invest more than 5% of the value of its total assets in the
    securities of any one issuer (other than obligations issued, or guaranteed
    by, the United States Government, its agencies or instrumentalities).
 
12
<PAGE>
        2. Purchase more than 10% of all outstanding voting securities or any
    class of securities of any one issuer.
 
        3. Invest more than 10% of its total assets in "illiquid securities"
    (securities for which market quotations are not readily available) and
    repurchase agreements which have a maturity of longer than seven days. The
    staff of the Securities and Exchange Commission ("SEC") has taken the
    position that purchased OTC options and the assets used as "cover" for
    written OTC options are illiquid securities. The Investment Manager
    disagrees with this position. Nevertheless, the Fund has agreed to treat OTC
    options and the covering assets thereon as illiquid securities for purposes
    of this investment restriction.
 
        4. Invest more than 5% of the value of its total assets in securities of
    issuers having a record, together with predecessors, of less than three
    years of continuous operation. This restriction shall not apply to any
    obligation of the United States Government, its agencies or
    instrumentalities.
 
        5. Purchase or sell commodities or commodities contracts except that the
    Fund may purchase or write interest rate futures contracts and related
    options thereon.
 
        6. Pledge its assets or assign or otherwise encumber them except to
    secure permitted borrowings. (For the purpose of this restriction,
    collateral arrangements with respect to the writing of options and
    collateral arrangements with respect to initial or variation margin for
    futures are not deemed to be pledges of assets.)
 
        7. Purchase securities on margin (but the Fund may obtain short-term
    loans as are necessary for the clearance of transactions). The deposit or
    payment by the Fund of initial or variation margin in connection with
    futures contracts or related options thereon is not considered the purchase
    of a security on margin.
 
        8. Borrow money, except from banks for investment purposes or as a
    temporary measure for extraordinary or emergency purposes in an amount up to
    25% of the Fund's total assets, within the limits set forth in the Act or
    enter into reverse repurchase agreements in an amount exceeding 10% of the
    Fund's total assets other than for purposes of meeting redemptions.
 
    If a percentage restriction is adhered to at the time of investment, a later
increase or decrease in percentage resulting from a change in values of
portfolio securities or amount of total or net assets will not be considered a
violation of any of the foregoing restrictions.
 
    Notwithstanding any other investment policy or restriction, the Fund may
seek to achieve its investment objective by investing all or substantially all
of its assets in another investment company having substantially the same
investment objective and policies as the Fund.
 
PURCHASE OF FUND SHARES
- --------------------------------------------------------------------------------
 
GENERAL
 
The Fund offers each class of its shares for sale to the public on a continuous
basis. Pursuant to a Distribution Agreement between the Fund and Dean Witter
Distributors Inc. (the "Distributor"), an affiliate of the Investment Manager,
shares of the Fund are distributed by the Distributor and offered by DWR and
other dealers who have entered into selected dealer agreements with the
Distributor ("Selected Broker-Dealers"). The principal executive office of the
Distributor is located at Two World Trade Center, New York, New York 10048.
 
    The Fund offers four classes of shares (each, a "Class"). Class A shares are
sold to investors with an initial sales charge that declines to zero for larger
purchases; however, Class A shares sold without an initial sales charge are
subject to a contingent deferred sales charge ("CDSC") of 1.0% if redeemed
within one year of purchase, except for certain specific circumstances. Class B
shares are sold without an initial sales charge but are subject to a CDSC
(scaled down from 5.0% to 1.0%) payable upon most redemptions within six years
after purchase. (Class B shares purchased by certain qualified
employer-sponsored benefit plans are subject to a CDSC scaled down from 2.0% to
1.0% if redeemed within three years after purchase.) Class C shares are sold
without an initial sales charge but are subject to a CDSC of 1.0% on most
redemptions made within one year after purchase. Class D shares are sold without
an initial sales charge or CDSC and are available only to investors meeting an
initial investment minimum of $5 million, and to certain other limited
categories of investors. At the discretion of the Board of Trustees of the Fund,
Class A shares may be sold to categories of investors in addition to those set
forth in this prospectus at net asset value without a front-end sales charge,
and Class D shares may be sold to certain other categories of investors, in each
case as may be described in the then current prospectus of the Fund. See
"Alternative Purchase Arrangements-- Selecting a Particular Class" for a
discussion of factors to consider in selecting which Class of shares to
purchase.
 
    The minimum initial purchase is $1,000 for each Class of shares, although
Class D shares are only available to persons investing $5 million or more and to
certain other limited categories of investors. For the purpose of meeting the
minimum $5 million initial investment for Class D shares, and subject to the
$1,000 minimum initial investment for each Class of the Fund, an investor's
existing
 
                                                                              13
<PAGE>
holdings of Class A shares of the Fund and other Dean Witter Funds that are
multiple class funds ("Dean Witter Multi-Class Funds") and shares of Dean Witter
Funds sold with a front-end sales charge ("FSC Funds") and concurrent
investments in Class D shares of the Fund and other Dean Witter Multi-Class
Funds will be aggregated. Subsequent purchases of $100 or more may be made by
sending a check, payable to Dean Witter Federal Securities Trust, directly to
Dean Witter Trust Company (the "Transfer Agent") at P.O. Box 1040, Jersey City,
NJ 07303 or by contacting an account executive of DWR or other Selected
Broker-Dealer. When purchasing shares of the Fund, investors must specify
whether the purchase is for Class A, Class B, Class C or Class D shares. If no
Class is specified, the Transfer Agent will not process the transaction until
the proper Class is identified. The minimum initial purchase in the case of
investments through EasyInvest-SM-, an automatic purchase plan (see "Shareholder
Services"), is $100, provided that the schedule of automatic investments will
result in investments totalling $1,000 within the first twelve months. In the
case of investments pursuant to Systematic Payroll Deduction Plans (including
Individual Retirement Plans), the Fund, in its discretion, may accept
investments without regard to any minimum amounts which would otherwise be
required, if the Fund has reason to believe that additional investments will
increase the investment in all accounts under such Plans to at least $1,000.
Certificates for shares purchased will not be issued unless requested by the
shareholder in writing to the Transfer Agent.
 
    Shares of the Fund are sold through the Distributor on a normal three
business day settlement basis; that is, payment is due on the third business day
(settlement date) after the order is placed with the Distributor. Shares of the
Fund purchased through the Distributor are entitled to dividends beginning on
the next business day following settlement date. Since DWR and other Selected
Broker-Dealers forward investors' funds on settlement date, they will benefit
from the temporary use of the funds if payment is made prior thereto. Shares
purchased through the Transfer Agent are entitled to dividends beginning on the
next business day following receipt of an order. As noted above, orders placed
directly with the Transfer Agent must be accompanied by payment. Investors will
be entitled to receive capital gains distributions if their order is received by
the close of business on the day prior to the record date for such
distributions. Sales personnel of a Selected Broker-Dealer are compensated for
selling shares of the Fund at the time of their sale by the Distributor or any
of its affiliates and/or the Selected Broker-Dealer. In addition, some sales
personnel of the Selected Broker-Dealer will receive various types of non-cash
compensation as special sales incentives, including trips, educational and/or
business seminars and merchandise. The Fund and the Distributor reserve the
right to reject any purchase orders.
 
ALTERNATIVE PURCHASE ARRANGEMENTS
 
The Fund offers several Classes of shares to investors designed to provide them
with the flexibility of selecting an investment best suited to their needs. The
general public is offered three Classes of shares: Class A shares, Class B
shares and Class C shares, which differ principally in terms of sales charges
and rate of expenses to which they are subject. A fourth Class of shares, Class
D shares, is offered only to limited categories of investors (see "No Load
Alternative--Class D Shares" below).
 
    Each Class A, Class B, Class C or Class D share of the Fund represents an
identical interest in the investment portfolio of the Fund except that Class A,
Class B and Class C shares bear the expenses of the ongoing shareholder service
fees, Class B and Class C shares bear the expenses of the ongoing distribution
fees and Class A, Class B and Class C shares which are redeemed subject to a
CDSC bear the expense of the additional incremental distribution costs resulting
from the CDSC applicable to shares of those Classes. The ongoing distribution
fees that are imposed on Class A, Class B and Class C shares will be imposed
directly against those Classes and not against all assets of the Fund and,
accordingly, such charges against one Class will not affect the net asset value
of any other Class or have any impact on investors choosing another sales charge
option. See "Plan of Distribution" and "Redemptions and Repurchases."
 
    Set forth below is a summary of the differences between the Classes and the
factors an investor should consider when selecting a particular Class. This
summary is qualified in its entirety by detailed discussion of each Class that
follows this summary.
 
CLASS A SHARES.  Class A shares are sold at net asset value plus an initial
sales charge of up to 4.25%. The initial sales charge is reduced for certain
purchases. Investments of $1 million or more (and investments by certain other
limited categories of investors) are not subject to any sales charges at the
time of purchase but are subject to a CDSC of 1.0% on redemptions made within
one year after purchase, except for certain specific circumstances. Class A
shares are also subject to a 12b-1 fee of up to 0.25% of the average daily net
assets of the Class. See "Initial Sales Charge Alternative--Class A Shares."
 
CLASS B SHARES.  Class B shares are offered at net asset value with no initial
sales charge but are subject to a CDSC (scaled down from 5.0% to 1.0%) if
redeemed within six years of purchase. (Class B shares purchased by certain
qualified employer-sponsored benefit plans are subject to a CDSC scaled down
from 2.0% to 1.0% if redeemed within three years after purchase.) This CDSC may
be waived for certain redemptions. Class B shares are also subject to an annual
12b-1 fee of 0.85% of the lesser of: (a) the average daily aggregate gross sales
of the Fund's Class B shares since the inception of the Fund (not including
reinvestments of dividends or capital gains distributions), less the
 
14
<PAGE>
average daily aggregate net asset value of the Fund's Class B shares redeemed
since the Fund's inception upon which a CDSC has been imposed or waived, or (b)
the average daily net assets of Class B. The Class B shares' distribution fee
will cause that Class to have higher expenses and pay lower dividends than Class
A or Class D shares.
 
    After approximately ten (10) years, Class B shares will convert
automatically to Class A shares of the Fund, based on the relative net asset
values of the shares of the two Classes on the conversion date. In addition, a
certain portion of Class B shares that have been acquired through the
reinvestment of dividends and distributions will be converted at that time. See
"Contingent Deferred Sales Charge Alternative--Class B Shares."
 
CLASS C SHARES.  Class C shares are sold at net asset value with no initial
sales charge but are subject to a CDSC of 1.0% on redemptions made within one
year after purchase. This CDSC may be waived for certain redemptions. They are
subject to an annual 12b-1 fee of up to 0.85% of the average daily net assets of
the Class C shares. The Class C shares' distribution fee may cause that Class to
have higher expenses and pay lower dividends than Class A or Class D shares. See
"Level Load Alternative--Class C Shares."
 
CLASS D SHARES.  Class D shares are available only to limited categories of
investors (see "No Load Alternative-- Class D Shares" below). Class D shares are
sold at net asset value with no initial sales charge or CDSC. They are not
subject to any 12b-1 fees. See "No Load Alternative-- Class D Shares."
 
SELECTING A PARTICULAR CLASS.  In deciding which Class of Fund shares to
purchase, investors should consider the following factors, as well as any other
relevant facts and circumstances:
 
    The decision as to which Class of shares is more beneficial to an investor
depends on the amount and intended length of his or her investment. Investors
who prefer an initial sales charge alternative may elect to purchase Class A
shares. Investors qualifying for significantly reduced or, in the case of
purchases of $1 million or more, no initial sales charges may find Class A
shares particularly attractive because similar sales charge reductions are not
available with respect to Class B or Class C shares. Moreover, Class A shares
are subject to lower ongoing expenses than are Class B or Class C shares over
the term of the investment. As an alternative, Class B and Class C shares are
sold without any initial sales charge so the entire purchase price is
immediately invested in the Fund. Any investment return on these additional
investment amounts may partially or wholly offset the higher annual expenses of
these Classes. Because the Fund's future return cannot be predicted, however,
there can be no assurance that this would be the case.
 
    Finally, investors should consider the effect of the CDSC period and any
conversion rights of the Classes in the context of their own investment time
frame. For example, although Class C shares are subject to a significantly lower
CDSC upon redemptions, they do not, unlike Class B shares, convert into Class A
shares after approximately ten years, and, therefore, are subject to an ongoing
12b-1 fee of 0.85% (rather than the 0.25% fee applicable to Class A shares) for
an indefinite period of time. Thus, Class B shares may be more attractive than
Class C shares to investors with longer term investment outlooks. Other
investors, however, may elect to purchase Class C shares if, for example, they
determine that they do not wish to be subject to a front-end sales charge and
they are uncertain as to the length of time they intend to hold their shares.
 
    For the purpose of meeting the $5 million minimum investment amount for
Class D shares, holdings of Class A shares in all Dean Witter Multi-Class Funds,
shares of FSC Funds and shares of Dean Witter Funds for which such shares have
been exchanged will be included together with the current investment amount.
 
    Sales personnel may receive different compensation for selling each Class of
shares. Investors should understand that the purpose of a CDSC is the same as
that of the initial sales charge in that the sales charges applicable to each
Class provide for the financing of the distribution of shares of that Class.
 
    Set forth below is a chart comparing the sales charge, 12b-1 fees and
conversion options applicable to each Class of shares:
 
<TABLE>
<CAPTION>
                                                   CONVERSION
  CLASS          SALES CHARGE         12b-1 FEE      FEATURE
<C>        <S>                        <C>        <C>
    A      Maximum 4.25% initial        0.25%          No
           sales charge reduced for
           purchases of $25,000 and
           over; shares sold without
           an initial sales charge
           generally subject to a
           1.0% CDSC during first
           year.
    B      Maximum 5.0% CDSC during     0.85%    B shares
           the first year decreasing             convert to A
           to 0 after six years                  shares
                                                 automatically
                                                 after
                                                 approximately
                                                 ten years
    C      1.0% CDSC during first       0.85%          No
           year
    D                None               None           No
</TABLE>
 
    See "Purchase of Fund Shares" and "The Fund and its Management" for a
complete description of the sales charges and service and distribution fees for
each Class of shares and "Determination of Net Asset Value," "Dividends,
Distributions and Taxes" and "Shareholder Services--Exchange Privilege" for
other differences between the Classes of shares.
 
                                                                              15
<PAGE>
INITIAL SALES CHARGE ALTERNATIVE-- CLASS A SHARES
 
Class A shares are sold at net asset value plus an initial sales charge. In some
cases, reduced sales charges may be available, as described below. Investments
of $1 million or more (and investments by certain other limited categories of
investors) are not subject to any sales charges at the time of purchase but are
subject to a CDSC of 1.0% on redemptions made within one year after purchase
(calculated from the last day of the month in which the shares were purchased),
except for certain specific circumstances. The CDSC will be assessed on an
amount equal to the lesser of the current market value or the cost of the shares
being redeemed. The CDSC will not be imposed (i) in the circumstances set forth
below in the section "Contingent Deferred Sales Charge Alternative--Class B
Shares-- CDSC Waivers," except that the references to six years in the first
paragraph of that section shall mean one year in the case of Class A shares, and
(ii) in the circumstances identified in the section "Additional Net Asset Value
Purchase Options" below. Class A shares are also subject to an annual 12b-1 fee
of up to 0.25% of the average daily net assets of the Class.
 
    The offering price of Class A shares will be the net asset value per share
next determined following receipt of an order (see "Determination of Net Asset
Value" below), plus a sales charge (expressed as a percentage of the offering
price) on a single transaction as shown in the following table:
 
<TABLE>
<CAPTION>
                                         SALES CHARGE
                             -------------------------------------
                               PERCENTAGE OF       APPROXIMATE
         AMOUNT OF            PUBLIC OFFERING     PERCENTAGE OF
    SINGLE TRANSACTION             PRICE         AMOUNT INVESTED
- ---------------------------  -----------------  ------------------
<S>                          <C>                <C>
Less than $25,000..........          4.25%               4.44%
$25,000 but less
  than $50,000.............          4.00%               4.17%
$50,000 but less
  than $100,000............          3.50%               3.63%
$100,000 but less
  than $250,000............          2.75%               2.83%
$250,000 but less
  than $1 million..........          1.75%               1.78%
$1 million and over........             0                   0
</TABLE>
 
    Upon notice to all Selected Broker-Dealers, the Distributor may reallow up
to the full applicable sales charge as shown in the above schedule during
periods specified in such notice. During periods when 90% or more of the sales
charge is reallowed, such Selected Broker-Dealers may be deemed to be
underwriters as that term is defined in the Securities Act of 1933.
 
    The above schedule of sales charges is applicable to purchases in a single
transaction by, among others: (a) an individual; (b) an individual, his or her
spouse and their children under the age of 21 purchasing shares for his, her or
their own accounts; (c) a trustee or other fiduciary purchasing shares for a
single trust estate or a single fiduciary account; (d) a pension, profit-sharing
or other employee benefit plan qualified or non-qualified under Section 401 of
the Internal Revenue Code; (e) tax-exempt organizations enumerated in Section
501(c)(3) or (13) of the Internal Revenue Code; (f) employee benefit plans
qualified under Section 401 of the Internal Revenue Code of a single employer or
of employers who are "affiliated persons" of each other within the meaning of
Section 2(a)(3)(c) of the Act; and for investments in Individual Retirement
Accounts of employees of a single employer through Systematic Payroll Deduction
plans; or (g) any other organized group of persons, whether incorporated or not,
provided the organization has been in existence for at least six months and has
some purpose other than the purchase of redeemable securities of a registered
investment company at a discount.
 
COMBINED PURCHASE PRIVILEGE.  Investors may have the benefit of reduced sales
charges in accordance with the above schedule by combining purchases of Class A
shares of the Fund in single transactions with the purchase of Class A shares of
other Dean Witter Multi-Class Funds and shares of FSC Funds. The sales charge
payable on the purchase of the Class A shares of the Fund, the Class A shares of
the other Dean Witter Multi-Class Funds and the shares of the FSC Funds will be
at their respective rates applicable to the total amount of the combined
concurrent purchases of such shares.
 
RIGHT OF ACCUMULATION.  The above persons and entities may benefit from a
reduction of the sales charges in accordance with the above schedule if the
cumulative net asset value of Class A shares purchased in a single transaction,
together with shares of the Fund and other Dean Witter Funds previously
purchased at a price including a front-end sales charge (including shares of the
Fund and other Dean Witter Funds acquired in exchange for those shares, and
including in each case shares acquired through reinvestment of dividends and
distributions), which are held at the time of such transaction, amounts to
$25,000 or more. If such investor has a cumulative net asset value of shares of
FSC Funds and Class A and Class D shares equal to at least $5 million, such
investor is eligible to purchase Class D shares subject to the $1,000 minimum
initial investment requirement of that Class of the Fund. See "No Load
Alternative--Class D Shares" below.
 
    The Distributor must be notified by DWR or a Selected Broker-Dealer or the
shareholder at the time a purchase order is placed that the purchase qualifies
for the reduced charge under the Right of Accumulation. Similar notification
must be made in writing by the dealer or shareholder when such an order is
placed by mail. The reduced sales charge will not be granted if: (a) such
notification is not furnished at the time of the order; or (b) a review of the
records of the Selected Broker-Dealer or the Transfer Agent fails to confirm the
investor's represented holdings.
 
LETTER OF INTENT.  The foregoing schedule of reduced sales charges will also be
available to investors who enter into a written Letter of Intent providing for
the purchase, within a thirteen-month period, of Class A shares of the Fund from
 
16
<PAGE>
DWR or other Selected Broker-Dealers. The cost of Class A shares of the Fund or
shares of other Dean Witter Funds which were previously purchased at a price
including a front-end sales charge during the 90-day period prior to the date of
receipt by the Distributor of the Letter of Intent, or of Class A shares of the
Fund or shares of other Dean Witter Funds acquired in exchange for shares of
such funds purchased during such period at a price including a front-end sales
charge, which are still owned by the shareholder, may also be included in
determining the applicable reduction.
 
ADDITIONAL NET ASSET VALUE PURCHASE OPTIONS.  In addition to investments of $1
million or more, Class A shares also may be purchased at net asset value by the
following:
 
    (1) trusts for which Dean Witter Trust Company ("DWTC") or Dean Witter Trust
FSB ("DWTFSB") (each of which is an affiliate of the Investment Manager)
provides discretionary trustee services;
 
    (2) persons participating in a fee-based program approved by the
Distributor, pursuant to which such persons pay an asset based fee for services
in the nature of investment advisory or administrative services (such
investments are subject to all of the terms and conditions of such programs,
which may include termination fees and restrictions on transferability of Fund
shares);
 
    (3) retirement plans qualified under Section 401(k) of the Internal Revenue
Code ("401(k) plans") and other employer-sponsored plans qualified under Section
401(a) of the Internal Revenue Code with at least 200 eligible employees and for
which DWTC or DWTFSB serves as Trustee or the 401(k) Support Services Group of
DWR serves as recordkeeper;
 
    (4) 401(k) plans and other employer-sponsored plans qualified under Section
401(a) of the Internal Revenue Code for which DWTC or DWTFSB serves as Trustee
or the 401(k) Support Services Group of DWR serves as recordkeeper whose Class B
shares have converted to Class A shares, regardless of the plan's asset size or
number of eligible employees;
 
    (5) investors who are clients of a Dean Witter account executive who joined
Dean Witter from another investment firm within six months prior to the date of
purchase of Fund shares by such investors, if the shares are being purchased
with the proceeds from a redemption of shares of an open-end proprietary mutual
fund of the account executive's previous firm which imposed either a front-end
or deferred sales charge, provided such purchase was made within sixty days
after the redemption and the proceeds of the redemption had been maintained in
the interim in cash or a money market fund; and
 
    (6) other categories of investors, at the discretion of the Board, as
disclosed in the then current prospectus of the Fund.
 
    No CDSC will be imposed on redemptions of shares purchased pursuant to
paragraphs (1), (2) or (5), above.
 
    For further information concerning purchases of the Fund's shares, contact
DWR or another Selected Broker-Dealer or consult the Statement of Additional
Information.
 
CONTINGENT DEFERRED SALES CHARGE ALTERNATIVE--CLASS B SHARES
 
Class B shares are sold at net asset value next determined without an initial
sales charge so that the full amount of an investor's purchase payment may be
immediately invested in the Fund. A CDSC, however, will be imposed on most Class
B shares redeemed within six years after purchase. The CDSC will be imposed on
any redemption of shares if after such redemption the aggregate current value of
a Class B account with the Fund falls below the aggregate amount of the
investor's purchase payments for Class B shares made during the six years (or,
in the case of shares held by certain employer-sponsored benefit plans, three
years) preceding the redemption. In addition, Class B shares are subject to an
annual 12b-1 fee of 0.85% of the lesser of: (a) the average daily aggregate
gross sales of the Fund's Class B shares since the inception of the Fund (not
including reinvestments of dividends or capital gains distributions), less the
average daily aggregate net asset value of the Fund's Class B shares redeemed
since the Fund's inception upon which a CDSC has been imposed or waived, or (b)
the average daily net assets of Class B.
 
    Except as noted below, Class B shares of the Fund which are held for six
years or more after purchase (calculated from the last day of the month in which
the shares were purchased) will not be subject to any CDSC upon redemption.
Shares redeemed earlier than six years after purchase may, however, be subject
to a CDSC which will be a percentage of the dollar amount of shares redeemed and
will be assessed on an amount equal to the lesser of the current market value or
the cost of the shares being redeemed. The size of this percentage will depend
upon how long the shares have been held, as set forth in the following table:
 
<TABLE>
<CAPTION>
               YEAR SINCE                 CDSC AS A PERCENTAGE
         PURCHASE PAYMENT MADE             OF AMOUNT REDEEMED
- ----------------------------------------  ---------------------
<S>                                       <C>
First...................................             5.0%
Second..................................             4.0%
Third...................................             3.0%
Fourth..................................             2.0%
Fifth...................................             2.0%
Sixth...................................             1.0%
Seventh and thereafter..................             None
</TABLE>
 
    In the case of Class B shares of the Fund held by 401(k) plans or other
employer-sponsored plans qualified under Section 401(a) of the Internal Revenue
Code for which DWTC or DWTFSB serves as Trustee or the 401(k) Support Services
Group of DWR serves as recordkeeper
 
                                                                              17
<PAGE>
and whose accounts are opened on or after July 28, 1997, shares held for three
years or more after purchase (calculated as described in the paragraph above)
will not be subject to any CDSC upon redemption. However, shares redeemed
earlier than three years after purchase may be subject to a CDSC (calculated as
described in the paragraph above), the percentage of which will depend on how
long the shares have been held, as set forth in the following table:
 
<TABLE>
<CAPTION>
               YEAR SINCE                 CDSC AS A PERCENTAGE
         PURCHASE PAYMENT MADE             OF AMOUNT REDEEMED
- ----------------------------------------  ---------------------
<S>                                       <C>
First...................................             2.0%
Second..................................             2.0%
Third...................................             1.0%
Fourth and thereafter...................             None
</TABLE>
 
CDSC WAIVERS.  A CDSC will not be imposed on: (i) any amount which represents an
increase in value of shares purchased within the six years (or, in the case of
shares held by certain employer-sponsored benefit plans, three years) preceding
the redemption; (ii) the current net asset value of shares purchased more than
six years (or, in the case of shares held by certain employer-sponsored benefit
plans, three years) prior to the redemption; and (iii) the current net asset
value of shares purchased through reinvestment of dividends or distributions
and/or shares acquired in exchange for shares of FSC Funds or of other Dean
Witter Funds acquired in exchange for such shares. Moreover, in determining
whether a CDSC is applicable it will be assumed that amounts described in (i),
(ii) and (iii) above (in that order) are redeemed first.
 
    In addition, the CDSC, if otherwise applicable, will be waived in the case
of:
 
    (1) redemptions of shares held at the time a shareholder dies or becomes
disabled, only if the shares are:  (a) registered either in the name of an
individual shareholder (not a trust), or in the names of such shareholder and
his or her spouse as joint tenants with right of survivorship; or  (b) held in a
qualified corporate or self-employed retirement plan, Individual Retirement
Account ("IRA") or Custodial Account under Section 403(b)(7) of the Internal
Revenue Code ("403(b) Custodial Account"), provided in either case that the
redemption is requested within one year of the death or initial determination of
disability;
 
    (2) redemptions in connection with the following retirement plan
distributions:  (a) lump-sum or other distributions from a qualified corporate
or self-employed retirement plan following retirement (or, in the case of a "key
employee" of a "top heavy" plan, following attainment of age 59 1/2); (b)
distributions from an IRA or 403(b) Custodial Account following attainment of
age 59 1/2; or (C) a tax-free return of an excess contribution to an IRA; and
 
    (3) all redemptions of shares held for the benefit of a participant in a
401(k) plan or other employer-sponsored plan qualified under Section 401(a) of
the Internal Revenue Code which offers investment companies managed by the
Investment Manager or its subsidiary, Dean Witter Services Company Inc., as
self-directed investment alternatives and for which DWTC or DWTFSB serves as
Trustee or the 401(k) Support Services Group of DWR serves as recordkeeper
("Eligible Plan"), provided that either: (a) the plan continues to be an
Eligible Plan after the redemption; or  (b) the redemption is in connection with
the complete termination of the plan involving the distribution of all plan
assets to participants.
 
    With reference to (1) above, for the purpose of determining disability, the
Distributor utilizes the definition of disability contained in Section 72(m)(7)
of the Internal Revenue Code, which relates to the inability to engage in
gainful employment. With reference to (2) above, the term "distribution" does
not encompass a direct transfer of IRA, 403(b) Custodial Account or retirement
plan assets to a successor custodian or trustee. All waivers will be granted
only following receipt by the Distributor of confirmation of the shareholder's
entitlement.
 
CONVERSION TO CLASS A SHARES.  All shares of the Fund held prior to July 28,
1997 have been designated Class B shares. Shares held before May 1, 1997 will
convert to Class A shares in May, 2007. In all other instances Class B shares
will convert automatically to Class A shares, based on the relative net asset
values of the shares of the two Classes on the conversion date, which will be
approximately ten (10) years after the date of the original purchase. The ten
year period is calculated from the last day of the month in which the shares
were purchased or, in the case of Class B shares acquired through an exchange or
a series of exchanges, from the last day of the month in which the original
Class B shares were purchased, provided that shares originally purchased before
May 1, 1997 will convert to Class A shares in May, 2007. The conversion of
shares purchased on or after May 1, 1997 will take place in the month following
the tenth anniversary of the purchase. There will also be converted at that time
such proportion of Class B shares acquired through automatic reinvestment of
dividends and distributions owned by the shareholder as the total number of his
or her Class B shares converting at the time bears to the total number of
outstanding Class B shares purchased and owned by the shareholder. In the case
of Class B shares held by a 401(k) plan or other employer-sponsored plan
qualified under Section 401(a) of the Internal Revenue Code and for which DWTC
or DWTFSB serves as Trustee or the 401(k) Support Services Group of DWR serves
as recordkeeper, the plan is treated as a single investor and all Class B shares
will convert to Class A shares on the conversion date of the first shares of a
Dean Witter Multi-Class Fund purchased by that plan. In the case of Class B
shares previously exchanged for shares of an "Exchange Fund" (see "Shareholder
Services--Exchange Privilege"), the period of time the shares were held in the
Exchange Fund (calculated from the last day of the month in which the Exchange
Fund shares were acquired) is excluded from the
 
18
<PAGE>
holding period for conversion. If those shares are subsequently re-exchanged for
Class B shares of a Dean Witter Multi-Class Fund, the holding period resumes on
the last day of the month in which Class B shares are reacquired.
 
    If a shareholder has received share certificates for Class B shares, such
certificates must be delivered to the Transfer Agent at least one week prior to
the date for conversion. Class B shares evidenced by share certificates that are
not received by the Transfer Agent at least one week prior to any conversion
date will be converted into Class A shares on the next scheduled conversion date
after such certificates are received.
 
    Effectiveness of the conversion feature is subject to the continuing
availability of a ruling of the Internal Revenue Service or an opinion of
counsel that (i) the conversion of shares does not constitute a taxable event
under the Internal Revenue Code, (ii) Class A shares received on conversion will
have a basis equal to the shareholder's basis in the converted Class B shares
immediately prior to the conversion, and (iii) Class A shares received on
conversion will have a holding period that includes the holding period of the
converted Class B shares. The conversion feature may be suspended if the ruling
or opinion is no longer available. In such event, Class B shares would continue
to be subject to Class B 12b-1 fees.
 
    Class B shares purchased before July 28, 1997 by trusts for which DWTC or
DWTFSB provides discretionary trustee services will convert to Class A shares on
or about August 29, 1997. The CDSC will not be applicable to such shares.
 
LEVEL LOAD ALTERNATIVE--
CLASS C SHARES
 
Class C shares are sold at net asset value next determined without an initial
sales charge but are subject to a CDSC of 1.0% on most redemptions made within
one year after purchase (calculated from the last day of the month in which the
shares were purchased). The CDSC will be assessed on an amount equal to the
lesser of the current market value or the cost of the shares being redeemed. The
CDSC will not be imposed in the circumstances set forth above in the section
"Contingent Deferred Sales Charge Alternative-- Class B Shares--CDSC Waivers,"
except that the references to six years in the first paragraph of that section
shall mean one year in the case of Class C shares. Class C shares are subject to
an annual 12b-1 fee of up to 0.85% of the average daily net assets of the Class.
Unlike Class B shares, Class C shares have no conversion feature and,
accordingly, an investor that purchases Class C shares will be subject to 12b-1
fees applicable to Class C shares for an indefinite period subject to annual
approval by the Fund's Board of Trustees and regulatory limitations.
 
NO LOAD ALTERNATIVE--
CLASS D SHARES
 
Class D shares are offered without any sales charge on purchase or redemption
and without any 12b-1 fee. Class D shares are offered only to investors meeting
an initial investment minimum of $5 million and the following categories of
investors: (i) investors participating in the InterCapital mutual fund asset
allocation program pursuant to which such persons pay an asset based fee; (ii)
persons participating in a fee-based program approved by the Distributor,
pursuant to which such persons pay an asset based fee for services in the nature
of investment advisory or administrative services (subject to all of the terms
and conditions of such programs, which may include termination fees and
restrictions on transferability of Fund shares); (iii) 401(k) plans established
by DWR and SPS Transaction Services, Inc. (an affiliate of DWR) for their
employees; (iv) certain Unit Investment Trusts sponsored by DWR; (v) certain
other open-end investment companies whose shares are distributed by the
Distributor; and (vi) other categories of investors, at the discretion of the
Board, as disclosed in the then current prospectus of the Fund. Investors who
require a $5 million minimum initial investment to qualify to purchase Class D
shares may satisfy that requirement by investing that amount in a single
transaction in Class D shares of the Fund and other Dean Witter Multi-Class
Funds, subject to the $1,000 minimum initial investment required for that Class
of the Fund. In addition, for the purpose of meeting the $5 million minimum
investment amount, holdings of Class A shares in all Dean Witter Multi-Class
Funds, shares of FSC Funds and shares of Dean Witter Funds for which such shares
have been exchanged will be included together with the current investment
amount. If a shareholder redeems Class A shares and purchases Class D shares,
such redemption may be a taxable event.
 
PLAN OF DISTRIBUTION
 
The Fund has adopted a Plan of Distribution pursuant to Rule 12b-1 under the Act
with respect to the distribution of Class A, Class B and Class C shares of the
Fund. In the case of Class A and Class C shares, the Plan provides that the Fund
will reimburse the Distributor and others for the expenses of certain activities
and services incurred by them specifically on behalf of those shares.
Reimbursements for these expenses will be made in monthly payments by the Fund
to the Distributor, which will in no event exceed amounts equal to payments at
the annual rates of 0.25% and 0.85% of the average daily net assets of Class A
and Class C, respectively. In the case of Class B shares, the Plan provides that
the Fund will pay the Distributor a fee, which is accrued daily and paid
monthly, at the annual rate of 0.85% of the lesser of: (a) the average daily
aggregate gross sales of the Fund's Class B shares since the inception of the
Fund (not including reinvestments of dividends or capital gains distributions),
less the average daily aggregate
 
                                                                              19
<PAGE>
net asset value of the Fund's Class B shares redeemed since the Fund's inception
upon which a CDSC has been imposed or waived, or (b) the average daily net
assets of Class B. The fee is treated by the Fund as an expense in the year it
is accrued. In the case of Class A shares, the entire amount of the fee
currently represents a service fee within the meaning of the NASD guidelines. In
the case of Class B and Class C shares, a portion of the fee payable pursuant to
the Plan, equal to 0.20% and 0.25% of the average daily net assets of each of
these Classes, respectively, is currently characterized as a service fee. A
service fee is a payment made for personal service and/or the maintenance of
shareholder accounts.
 
    Additional amounts paid under the Plan in the case of Class B and Class C
shares are paid to the Distributor for services provided and the expenses borne
by the Distributor and others in the distribution of the shares of those
Classes, including the payment of commissions for sales of the shares of those
Classes and incentive compensation to and expenses of DWR's account executives
and others who engage in or support distribution of shares or who service
shareholder accounts, including overhead and telephone expenses; printing and
distribution of prospectuses and reports used in connection with the offering of
the Fund's shares to other than current shareholders; and preparation, printing
and distribution of sales literature and advertising materials. In addition, the
Distributor may utilize fees paid pursuant to the Plan in the case of Class B
shares to compensate DWR and other Selected Broker-Dealers for their opportunity
costs in advancing such amounts, which compensation would be in the form of a
carrying charge on any unreimbursed expenses.
 
    For the fiscal year ended October 31, 1996, Class B shares of the Fund
accrued payments under the Plan amounting to $6,554,450, which amount is equal
to 0.85% of the Fund's average daily net assets for the fiscal year. The
payments accrued under the Plan were calculated pursuant to clause (b) of the
compensation formula under the Plan. All shares held prior to July 28, 1997 have
been designated Class B shares.
 
    In the case of Class B shares, at any given time, the expenses in
distributing Class B shares of the Fund may be in excess of the total of (i) the
payments made by the Fund pursuant to the Plan, and (ii) the proceeds of CDSCs
paid by investors upon the redemption of Class B shares. For example, if $1
million in expenses in distributing Class B shares of the Fund had been incurred
and $750,000 had been received as described in (i) and (ii) above, the excess
expense would amount to $250,000. The Distributor has advised the Fund that such
excess amounts, including the carrying charge described above, totalled
$27,489,031 at October 31, 1996, which was equal to 3.82% of the net assets of
the Fund on such date. Because there is no requirement under the Plan that the
Distributor be reimbursed for all distribution expenses or any requirement that
the Plan be continued from year to year, such excess amount does not constitute
a liability of the Fund. Although there is no legal obligation for the Fund to
pay expenses incurred in excess of payments made to the Distributor under the
Plan, and the proceeds of CDSCs paid by investors upon redemption of shares, if
for any reason the Plan is terminated the Trustees will consider at that time
the manner in which to treat such expenses. Any cumulative expenses incurred,
but not yet recovered through distribution fees or CDSCs, may or may not be
recovered through future distribution fees or CDSCs.
 
    In the case of Class A and Class C shares, expenses incurred pursuant to the
Plan in any calendar year in excess of 0.25% or 0.85% of the average daily net
assets of Class A or Class C, respectively, will not be reimbursed by the Fund
through payments in any subsequent year, except that expenses representing a
gross sales commission credited to account executives at the time of sale may be
reimbursed in the subsequent calendar year. No interest or other financing
charges will be incurred on any Class A or Class C distribution expenses
incurred by the Distributor under the Plan or on any unreimbursed expenses due
to the Distributor pursuant to the Plan.
 
DETERMINATION OF NET ASSET VALUE
 
The net asset value per share is determined once daily at 4:00 p.m., New York
time (or, on days when the New York Stock Exchange closes prior to 4:00 p.m., at
such earlier time), on each day that the New York Stock Exchange is open by
taking the net assets of the Fund, dividing by the number of shares outstanding
and adjusting to the nearest cent. The assets belonging to the Class A, Class B,
Class C and Class D shares will be invested together in a single portfolio. The
net asset value of each Class, however, will be determined separately by
subtracting each Class's accrued expenses and liabilities. The net asset value
per share will not be determined on Good Friday and on such other federal and
non-federal holidays as are observed by the New York Stock Exchange.
 
    In the calculation of the Fund's net asset value: (1) all portfolio
securities for which over-the-counter market quotations are readily available
are valued at the latest bid price prior to the time of valuation, and (2) when
market quotations are not readily available, including circumstances under which
it is determined by the Investment Manager that sale or bid prices are not
reflective of a security's market value, portfolio securities are valued at
their fair value as determined in good faith under procedures established by and
under the general supervision of the Fund's Trustees (valuation of securities
for which market quotations are not readily available may also be based upon
current market prices of securities which are comparable in coupon, rating and
maturity or an appropriate matrix utilizing similar factors).
 
    Short-term debt securities with remaining maturities of sixty days or less
at the time of purchase are valued at
 
20
<PAGE>
amortized cost, unless the Trustees determine such does not reflect the
securities' market value, in which case these securities will be valued at their
fair value as determined by the Trustees. The value of other assets will be
determined in good faith under procedures established by and under the
supervision of the Trustees.
 
    Certain of the Fund's portfolio securities may be valued by an outside
pricing service approved by the Fund's Trustees. The pricing service may utilize
a matrix system incorporating security quality, maturity and coupon as the
evaluation model parameters, and/or research evaluations by its staff, including
review of broker-dealer market price quotations, in determining what it believes
is the fair valuation of the portfolio securities valued by such pricing
service.
 
SHAREHOLDER SERVICES
- --------------------------------------------------------------------------------
 
AUTOMATIC INVESTMENT OF DIVIDENDS AND DISTRIBUTIONS.  All income dividends and
capital gains distributions are automatically paid in full and fractional shares
of the applicable Class of the Fund (or, if specified by the shareholder, in
shares of any other open-end Dean Witter Fund), unless the shareholder requests
that they be paid in cash. Shares so acquired are acquired at net asset value
and are not subject to the imposition of a front-end sales charge or a CDSC (see
"Redemptions and Repurchases"). Such dividends and distributions will be paid,
at the net asset value per share, in shares of the applicable Class of the Fund
(or in cash if the shareholder so requests) on the monthly payment date, which
will be no later than the last business day of the month for which the dividend
or distribution is payable. Processing of dividend checks begins immediately
following the monthly payment date. Shareholders who have requested to receive
dividends in cash will normally receive their monthly dividend check during the
first ten days of the following month.
 
INVESTMENT OF DIVIDENDS AND DISTRIBUTIONS RECEIVED IN CASH.  Any shareholder who
receives a cash payment representing a dividend or capital gains distribution
may invest such dividend or distribution in shares of the applicable Class at
the net asset value per share next determined after receipt by the Transfer
Agent, by returning the check or the proceeds to the Transfer Agent within
thirty days after the payment date. Shares so acquired are acquired at net asset
value and are not subject to the imposition of a front-end sales charge or a
CDSC (see "Redemptions and Repurchases.")
 
EASYINVEST-SM-.  Shareholders may subscribe to EasyInvest, an automatic purchase
plan which provides for any amount from $100 to $5,000 to be transferred
automatically from a checking or savings account or following redemption of
shares of a Dean Witter money market fund, on a semi-monthly, monthly or
quarterly basis, to the Transfer Agent for investment in shares of the Fund (see
"Purchase of Fund Shares" and "Redemptions and Repurchases--Involuntary
Redemption").
 
SYSTEMATIC WITHDRAWAL PLAN.  A systematic withdrawal plan (the "Withdrawal
Plan") is available for shareholders who own or purchase shares of the Fund
having a minimum value of $10,000 based upon the then current net asset value.
The Withdrawal Plan provides for monthly or quarterly (March, June, September
and December) checks in any dollar amount, not less than $25, or in any whole
percentage of the account balance, on an annualized basis. Any applicable CDSC
will be imposed on shares redeemed under the Withdrawal Plan (see "Purchase of
Fund Shares"). Therefore, any shareholder participating in the Withdrawal Plan
will have sufficient shares redeemed from his or her account so that the
proceeds (net of any applicable CDSC) to the shareholder will be the designated
monthly or quarterly amount. Withdrawal plan payments should not be considered
as dividends, yields or income. If periodic withdrawal plan payments
continuously exceed net investment income and net capital gains, the
shareholder's original investment will be correspondingly reduced and ultimately
exhausted. Each withdrawal constitutes a redemption of shares and any gain or
loss realized must be recognized for federal income tax purposes.
 
    Shareholders should contact their DWR or other Selected Broker-Dealer
account executive or the Transfer Agent for further information about any of the
above services.
 
TAX-SHELTERED RETIREMENT PLANS.  Retirement plans are available through the
Distributor for use by corporations, the self-employed, Individual Retirement
Accounts and Custodial Accounts under Section 403(b)(7) of the Internal Revenue
Code. Adoption of such plans should be on advice of legal counsel or tax
adviser.
 
    For further information regarding plan administration, custodial fees and
other details, investors should contact their account executive or the Fund.
 
EXCHANGE PRIVILEGE
 
Shares of each Class may be exchanged for shares of the same Class of any other
Dean Witter Multi-Class Fund without the imposition of any exchange fee. Shares
may also be exchanged for shares of the following funds: Dean Witter Short-Term
U.S. Treasury Trust, Dean Witter Limited Term Municipal Trust, Dean Witter
Short-Term Bond Fund, Dean Witter Intermediate Term U.S. Treasury Trust and five
Dean Witter funds which are money market funds (the "Exchange Funds"). Class A
shares may also be exchanged for shares of Dean Witter Multi-State Municipal
Series Trust and Dean Witter Hawaii Municipal Trust,
 
                                                                              21
<PAGE>
which are Dean Witter Funds sold with a front-end sales charge ("FSC Funds").
Class B shares may also be exchanged for shares of Dean Witter Global Short-Term
Income Fund Inc., Dean Witter High Income Securities and Dean Witter National
Municipal Trust, which are Dean Witter Funds offered with a CDSC ("CDSC Funds").
Exchanges may be made after the shares of the Fund acquired by purchase (not by
exchange or dividend reinvestment) have been held for thirty days. There is no
waiting period for exchanges of shares acquired by exchange or dividend
reinvestment.
 
    An exchange to another Dean Witter Multi-Class Fund, any FSC Fund, any CDSC
Fund or any Exchange Fund that is not a money market fund is on the basis of the
next calculated net asset value per share of each fund after the exchange order
is received. When exchanging into a money market fund from the Fund, shares of
the Fund are redeemed out of the Fund at their next calculated net asset value
and the proceeds of the redemption are used to purchase shares of the money
market fund at their net asset value determined the following business day.
Subsequent exchanges between any of the money market funds and any of the Dean
Witter Multi-Class Funds, FSC Funds or CDSC Funds or any Exchange Fund that is
not a money market fund can be effected on the same basis.
 
    No CDSC is imposed at the time of any exchange of shares, although any
applicable CDSC will be imposed upon ultimate redemption. During the period of
time the shareholder remains in an Exchange Fund (calculated from the last day
of the month in which the Exchange Fund shares were acquired), the holding
period (for the purpose of determining the rate of the CDSC) is frozen. If those
shares are subsequently re-exchanged for shares of a Dean Witter Multi-Class
Fund or shares of a CDSC Fund, the holding period previously frozen when the
first exchange was made resumes on the last day of the month in which shares of
a Dean Witter Multi-Class Fund or shares of a CDSC Fund are reacquired. Thus,
the CDSC is based upon the time (calculated as described above) the shareholder
was invested in shares of a Dean Witter Multi-Class Fund or in shares of a CDSC
Fund (see "Purchase of Fund Shares"). In the case of exchanges of Class A shares
which are subject to a CDSC, the holding period also includes the time
(calculated as described above) the shareholder was invested in shares of a FSC
Fund. However, in the case of shares exchanged into an Exchange Fund on or after
April 23, 1990, upon a redemption of shares which results in a CDSC being
imposed, a credit (not to exceed the amount of the CDSC) will be given in an
amount equal to the Exchange Fund 12b-1 distribution fees incurred on or after
that date which are attributable to those shares. (Exchange Fund 12b-1
distribution fees are described in the prospectuses for those funds.) Class B
shares of the Fund acquired in exchange for Class B shares of another Dean
Witter Multi-Class Fund or shares of a CDSC Fund having a different CDSC
schedule than that of this Fund will be subject to the higher CDSC schedule,
even if such shares are subsequently re-exchanged for shares of the fund with
the lower CDSC schedule.
 
ADDITIONAL INFORMATION REGARDING EXCHANGES.  Purchases and exchanges should be
made for investment purposes only. A pattern of frequent exchanges may be deemed
by the Investment Manager to be abusive and contrary to the best interests of
the Fund's other shareholders and, at the Investment Manager's discretion, may
be limited by the Fund's refusal to accept additional purchases and/or exchanges
from the investor. Although the Fund does not have any specific definition of
what constitutes a pattern of frequent exchanges, and will consider all relevant
factors in determining whether a particular situation is abusive and contrary to
the best interests of the Fund and its other shareholders, investors should be
aware that the Fund and each of the other Dean Witter Funds may in their
discretion limit or otherwise restrict the number of times this Exchange
Privilege may be exercised by any investor. Any such restriction will be made by
the Fund on a prospective basis only, upon notice to the shareholder not later
than ten days following such shareholder's most recent exchange. Also, the
Exchange Privilege may be terminated or revised at any time by the Fund and/or
any of such Dean Witter Funds for which shares of the Fund have been exchanged,
upon such notice as may be required by applicable regulatory agencies.
Shareholders maintaining margin accounts with DWR or another Selected
Broker-Dealer are referred to their account executive regarding restrictions on
exchange of shares of the Fund pledged in the margin account.
 
    The current prospectus for each fund describes its investment objective(s)
and policies, and shareholders should obtain a copy and examine it carefully
before investing. Exchanges are subject to the minimum investment requirement of
each Class of shares and any other conditions imposed by each fund. In the case
of a shareholder holding a share certificate or certificates, no exchanges may
be made until all applicable share certificates have been received by the
Transfer Agent and deposited in the shareholder's account. An exchange will be
treated for federal income tax purposes the same as a repurchase or redemption
of shares, on which the shareholder may realize a capital gain or loss. However,
the ability to deduct capital losses on an exchange may be limited in situations
where there is an exchange of shares within ninety days after the shares are
purchased. The Exchange Privilege is only available in states where an exchange
may legally be made.
 
    If DWR or another Selected Broker-Dealer is the current dealer of record and
its account numbers are part of the account information, shareholders may
initiate an exchange of shares of the Fund for shares of any of the Dean Witter
Funds (for which the Exchange Privilege is available) pursuant to this Exchange
Privilege by contacting their account executive (no Exchange Privilege
Authorization Form is required). Other shareholders (and those shareholders who
are clients of DWR or another Selected
 
22
<PAGE>
Broker-Dealer but who wish to make exchanges directly by writing or telephoning
the Transfer Agent) must complete and forward to the Transfer Agent an Exchange
Privilege Authorization Form, copies of which may be obtained from the Transfer
Agent, to initiate an exchange. If the Authorization Form is used, exchanges may
be made in writing or by contacting the Transfer Agent at (800) 869-NEWS
(toll-free).
 
    The Fund will employ reasonable procedures to confirm that exchange
instructions communicated over the telephone are genuine. Such procedures may
include requiring various forms of personal identification such as name, mailing
address, social security or other tax identification number and DWR or other
Selected Broker-Dealer account number (if any). Telephone instructions may also
be recorded. If such procedures are not employed, the Fund may be liable for any
losses due to unauthorized or fraudulent instructions.
 
    Telephone exchange instructions will be accepted if received by the Transfer
Agent between 9:00 a.m. and 4:00 p.m., New York time, on any day the New York
Stock Exchange is open. Any shareholder wishing to make an exchange who has
previously filed an Exchange Privilege Authorization Form and who is unable to
reach the Fund by telephone should contact his or her DWR or other Selected
Broker-Dealer account executive, if appropriate, or make a written exchange
request. Shareholders are advised that during periods of drastic economic or
market changes, it is possible that the telephone exchange procedures may be
difficult to implement, although this has not been the case with the Dean Witter
Funds in the past.
 
    Shareholders should contact their DWR or other Selected Broker-Dealer
account executive or the Transfer Agent for further information about the
Exchange Privilege.
 
REDEMPTIONS AND REPURCHASES
- --------------------------------------------------------------------------------
 
REDEMPTION.  Shares of each Class of the Fund can be redeemed for cash at any
time at the net asset value per share next determined less the amount of any
applicable CDSC in the case of Class A, Class B or Class C shares (see "Purchase
of Fund Shares"). If shares are held in a shareholder's account without a share
certificate, a written request for redemption to the Fund's Transfer Agent at
P.O. Box 983, Jersey City, NJ 07303 is required. If certificates are held by the
shareholder(s), the shares may be redeemed by surrendering the certificate(s)
with a written request for redemption, along with any additional information
required by the Transfer Agent.
 
REPURCHASE.  DWR and other Selected Broker-Dealers are authorized to repurchase
shares represented by a share certificate which is delivered to any of their
offices. Shares held in a shareholder's account without a share certificate may
also be repurchased by DWR and other Selected Broker-Dealers upon the telephonic
request of the shareholder. The repurchase price is the net asset value next
computed (see "Purchase of Fund Shares") after such repurchase order is received
by DWR or other Selected Broker-Dealer, reduced by any applicable CDSC.
 
    The CDSC, if any, will be the only fee imposed upon repurchase by the Fund
or the Distributor. The offer by DWR and other Selected Broker-Dealers to
repurchase shares may be suspended without notice by them at any time. In that
event, shareholders may redeem their shares through the Fund's Transfer Agent as
set forth above under "Redemption."
 
PAYMENT FOR SHARES REDEEMED OR REPURCHASED.  Payment for shares presented for
repurchase or redemption will be made by check within seven days after receipt
by the Transfer Agent of the certificate and/or written request in good order.
Such payment may be postponed or the right of redemption suspended under unusual
circumstances; e.g., when normal trading is not taking place on the New York
Stock Exchange. If the shares to be redeemed have recently been purchased by
check, payment of the redemption proceeds may be delayed for the minimum time
needed to verify that the check used for investment has been honored (not more
than fifteen days from the time of receipt of the check by the Transfer Agent).
Shareholders maintaining margin accounts with DWR or another Selected
Broker-Dealer are referred to their account executive regarding restrictions on
redemption of shares of the Fund pledged in the margin account.
 
REINSTATEMENT PRIVILEGE.  A shareholder who has had his or her shares redeemed
or repurchased and has not previously exercised this reinstatement privilege
may, within 35 days after the date of the redemption or repurchase, reinstate
any portion or all of the proceeds of such redemption or repurchase in shares of
the Fund in the same Class from which such shares were redeemed or repurchased,
at the net asset value next determined after a reinstatement request, together
with the proceeds, is received by the Transfer Agent and receive a pro rata
credit for any CDSC paid in connection with such redemption or repurchase.
 
INVOLUNTARY REDEMPTION.  The Fund reserves the right, on sixty days' notice, to
redeem, at their net asset value, the shares of any shareholder (other than
shares held in an Individual Retirement Account or Custodial Account under
Section 403(b)(7) of the Internal Revenue Code) whose shares due to redemptions
by the shareholder have a value of less than $100 or such lesser amount as may
be fixed by the Trustees or, in the case of an account opened through
EasyInvest-SM-, if after twelve months the shareholder has invested less than
$1,000 in the account. However, before the Fund redeems such shares and sends
the proceeds to the shareholder, it will notify the shareholder that the value
 
                                                                              23
<PAGE>
of the shares is less than the applicable amount and allow him or her sixty days
to make an additional investment in an amount which will increase the value of
his of her account to at least the applicable amount before the redemption is
processed. No CDSC will be imposed on any involuntary redemption.
 
DIVIDENDS, DISTRIBUTIONS AND TAXES
- --------------------------------------------------------------------------------
 
DIVIDENDS AND DISTRIBUTIONS.  The Fund declares dividends separately for each
Class of shares and declares dividends from net investment income on each day
the New York Stock Exchange is open for business to shareholders of record as of
the close of business the preceding business day. Such dividends are paid
monthly.
 
    The Fund may pay quarterly dividends of realized net short-term capital
gains, if any. Such dividends may include a portion of the premiums received by
the Fund from expired call and put options written by the Fund on U.S.
Government securities, and of the net gains realized on closing purchase
transactions with respect to such options. The Fund may elect to retain a
portion of any net short-term capital gains for reinvestment. Net realized
long-term capital gains, if any, will be distributed at least once per year,
although the Investment Manager reserves the right to retain a portion of such
gains for reinvestment.
 
    As of October 31, 1996, the Fund had a net capital loss carryover of
approximately $58,206,000. To the extent of such carryover, the Fund could
retain gains realized in future years without either the Fund or its
shareholders being required to pay a tax on such gains. However, the Fund may
distribute to shareholders realized gains. Such distributions could,
notwithstanding the loss carryover, be taxable to shareholders to the extent of
the Fund's realized gains. Also, the Fund may at times make payments from
sources other than income or net capital gains. Payments from such sources will,
in effect, represent a return of a portion of each shareholder's investment.
All, or a portion, of such payments will not be taxable to shareholders.
 
    All dividends and capital gains distributions will be paid in additional
shares of the same Class and automatically credited to the shareholder's account
without issuance of a share certificate unless the shareholder requests in
writing that all dividends be paid in cash. Shares acquired by dividend and
distribution reinvestments will not be subject to any front-end sales charge or
CDSC. Class B shares acquired through dividend and distribution reinvestments
will become eligible for conversion to Class A shares on a pro rata basis.
Distributions paid on Class A and Class D shares will be higher than for Class B
and Class C shares because distribution fees paid by Class B and Class C shares
are higher. (See "Shareholder Services--Automatic Investment of Dividends and
Distributions".)
 
TAXES.  Because the Fund intends to distribute all of its net investment income
and net short-term capital gains to shareholders and otherwise continue to
qualify as a regulated investment company under Subchapter M of the Internal
Revenue Code, it is not expected that the Fund will be required to pay any
federal income tax on such income and capital gains.
 
    Gains or losses on the Fund's transactions in listed options on securities,
futures and options on futures may be treated as 60% long-term and 40%
short-term. When the Fund engages in options and futures transactions, various
tax regulations applicable to the Fund may have the effect of causing the Fund
to recognize a gain or loss for tax purposes before that gain or loss is
realized, or to defer recognition of a realized loss for tax purposes.
Recognition, for tax purposes, of an unrealized loss may result in a lesser
amount of the Fund's realized net short-term gains being available for quarterly
distribution.
 
    As a regulated investment company, the Fund is subject to the requirement
that less than 30% of its gross income be derived from the sale or other
disposition of securities held for less than three months. Accordingly, the Fund
may be restricted in the writing of options on securities held for less than
three months, in the writing of options which expire in less than three months,
and in effecting closing transactions with respect to call or put options which
have been written or purchased less than three months prior to such
transactions. The Fund may also be restricted in its ability to engage in
transactions involving futures contracts.
 
    Shareholders who are required to pay taxes on their income will normally
have to pay federal income taxes, and any applicable state and/or local income
taxes, on the dividends and distributions they receive from the Fund. Such
dividends and distributions, to the extent that they are derived from net
investment income and net short-term capital gains, are taxable to the
shareholder as ordinary dividend income regardless of whether the shareholder
receives such distributions in additional shares or in cash. Any dividends
declared in the last quarter of any calendar year which are paid in the
following year prior to February 1 will be deemed, for tax purposes, to have
been received by the shareholder in the prior year.
 
    Distributions of net long-term capital gains, if any, are taxable to
shareholders as long-term capital gains regardless of how long a shareholder has
held the Fund's shares and regardless of whether the distribution is received in
additional shares or in cash. Capital gains distributions are not eligible for
the corporate dividends received deduction.
 
    After the end of the calendar year, shareholders will be sent full
information on their dividends and capital gains distributions for tax purposes.
To avoid being subject to a 31% federal backup withholding tax on taxable
dividends, distributions and the proceeds of redemptions and
 
24
<PAGE>
repurchases, shareholders' taxpayer identification numbers must be furnished and
certified as to their accuracy.
 
    The foregoing discussion relates solely to the federal income tax
consequences of an investment in the Fund. Distributions may also be subject to
state and local taxes; therefore, each shareholder is advised to consult his or
her own tax adviser.
 
PERFORMANCE INFORMATION
- --------------------------------------------------------------------------------
 
From time to time the Fund may quote its "yield" and/or its "total return" in
advertisements and sales literature. These figures are computed separately for
Class A, Class B, Class C and Class D shares. Both the yield and the total
return of the Fund are based on historical earnings and are not intended to
indicate future performance. The yield of each Class of the Fund is computed by
dividing the Class's net investment income over a 30-day period by an average
value (using the average number of shares entitled to receive dividends and the
maximum offering price per share at the end of the period), all in accordance
with applicable regulatory requirements. Such amount is compounded for six
months and then annualized for a twelve-month period to derive the Fund's yield
for each Class.
 
    The "average annual total return" of the Fund refers to a figure reflecting
the average annualized percentage increase (or decrease) in the value of an
initial investment in a Class of the Fund of $1,000 over periods of one, five
and ten years, or the life of the Fund, if less than any of the foregoing.
Average annual total return reflects all income earned by the Fund, any
appreciation or depreciation of the Fund's assets, all expenses incurred by the
applicable Class and all sales charges incurred by shareholders, for the stated
periods. It also assumes reinvestment of all dividends and distributions paid by
the Fund.
 
    In addition to the foregoing, the Fund may advertise its total return for
each Class over different periods of time by means of aggregate, average,
year-by-year or other types of total return figures. Such calculations may or
may not reflect the deduction of any sales charge which, if reflected, would
reduce the performance quoted. The Fund may also advertise the growth of
hypothetical investments of $10,000, $50,000 and $100,000 in each Class of
shares of the Fund. The Fund from time to time may also advertise its
performance relative to certain performance rankings and indexes compiled by
independent organizations (such as Lipper Analytical Services, Inc. and Salomon
Brothers Treasury Index, Shearson Lehman Government Bond Index, Merrill Lynch
Mortgage Master Index and Donahue's Money Market Index).
 
ADDITIONAL INFORMATION
- --------------------------------------------------------------------------------
 
VOTING RIGHTS.  All shares of beneficial interest of the Fund are of $0.01 par
value and are equal as to earnings, assets and voting privileges except that
each Class will have exclusive voting privileges with respect to matters
relating to distribution expenses borne solely by such Class or any other matter
in which the interests of one Class differ from the interests of any other
Class. In addition, Class B shareholders will have the right to vote on any
proposed material increase in Class A's expenses, if such proposal is submitted
separately to Class A shareholders. Also, as discussed herein, Class A, Class B
and Class C bear the expenses related to the distribution of their respective
shares.
 
    The Fund is not required to hold Annual Meetings of Shareholders and in
ordinary circumstances the Fund does not intend to hold such meetings. The
Trustees may call Special Meetings of Shareholders for action by shareholder
vote as may be required by the Act or the Declaration of Trust. Under certain
circumstances the Trustees may be removed by action of the Trustees or by the
shareholders.
 
    Under Massachusetts law, shareholders of a business trust may, under certain
circumstances, be held personally liable as partners for the obligations of the
Fund. However, the Declaration of Trust contains an express disclaimer of
shareholder liability for acts or obligations of the Fund, requires that Fund
obligations include such disclaimer, and provides for indemnification and
reimbursement of expenses out of the Fund's property for any shareholder held
personally liable for the obligations of the Fund. Thus, the risk of a
shareholder incurring financial loss on account of shareholder liability is
limited to circumstances in which the Fund itself would be unable to meet its
obligations. Given the above limitations on shareholder personal liability, and
the nature of the Fund's assets and operations, the possibility of the Fund
being unable to meet its obligations is remote and, in the opinion of
Massachusetts counsel to the Fund, the risk to Fund shareholders of personal
liability is remote.
 
CODE OF ETHICS.  Directors, officers and employees of InterCapital, Dean Witter
Services Company Inc. and the Distributor are subject to a strict Code of Ethics
adopted by those companies. The Code of Ethics is intended to ensure that the
interests of shareholders and other clients are placed ahead of any personal
interest, that no undue personal benefit is obtained from a person's employment
activities and that actual and potential conflicts of interest are avoided. To
achieve these goals and comply with regulatory requirements, the Code of Ethics
requires, among other things, that personal securities transactions by employees
of the companies be subject to an advance clearance
 
                                                                              25
<PAGE>
process to monitor that no Dean Witter Fund is engaged at the same time in a
purchase or sale of the same security. The Code of Ethics bans the purchase of
securities in an initial public offering, and also prohibits engaging in futures
and options transactions and profiting on short-term trading (that is, a
purchase within sixty days of a sale or a sale within sixty days of a purchase)
of a security. In addition, investment personnel may not purchase or sell a
security for their personal account within thirty days before or after any
transaction in any Dean Witter Fund managed by them. Any violations of the Code
of Ethics are subject to sanctions, including reprimand, demotion or suspension
or termination of employment. The Code of Ethics comports with regulatory
requirements and the recommendations in the 1994 report by the Investment
Company Institute Advisory Group on Personal Investing.
 
MASTER/FEEDER CONVERSION.  The Fund reserves the right to seek to achieve its
investment objective by investing all of its investable assets in a diversified,
open-end management investment company having the same investment objective and
policies and substantially the same investment restrictions as those applicable
to the Fund.
 
SHAREHOLDER INQUIRIES.  All inquiries regarding the Fund should be directed to
the Fund at the telephone numbers or address set forth on the front cover of
this Prospectus.
 
26
<PAGE>
DEAN WITTER
FEDERAL SECURITIES TRUST
TWO WORLD TRADE CENTER
NEW YORK, NEW YORK 10048
 
TRUSTEES
Michael Bozic
Charles A. Fiumefreddo
Edwin J. Garn
John R. Haire
Dr. Manuel H. Johnson
Michael E. Nugent
Philip J. Purcell
John L. Schroeder
 
OFFICERS
Charles A. Fiumefreddo
Chairman and Chief Executive Officer
Barry Fink
Vice President, Secretary and
General Counsel
Rajesh K. Gupta
Vice President
Thomas F. Caloia
Treasurer
 
CUSTODIAN
The Bank of New York
90 Washington Street
New York, New York 10286
 
TRANSFER AGENT AND
DIVIDEND DISBURSING AGENT
Dean Witter Trust Company
Harborside Financial Center
Plaza Two
Jersey City, New Jersey 07311
 
INDEPENDENT ACCOUNTANTS
Price Waterhouse LLP
1177 Avenue of the Americas
New York, New York 10036
 
INVESTMENT MANAGER
Dean Witter InterCapital Inc.
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