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                                                                    Exhibit 10.1



                       NATURAL MICROSYSTEMS CORPORATION

                 1993 NON-EMPLOYEE DIRECTORS STOCK OPTION PLAN
                (Amended and Restated Effective March 12, 1999)

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1.   PURPOSE
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          The purpose of this Natural MicroSystems Corporation 1993 Non-Employee
Director Stock Option Plan (the "Plan") is to enable Natural MicroSystems
Corporation (the "Company") to attract and retain non-employee directors and
further align their interests with those of the shareholders by providing for or
increasing their equity interests in the Company.

2.   ADMINISTRATION
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          This Plan shall be administered by the Board of Directors of the
Company (the "Board") or by the Compensation Committee appointed by the Board
(the "Committee"). In the event the Board refrains from delegating
administration of this Plan to the Committee, the Board shall have all power and
authority to administer this Plan. In such event, the word "Committee" wherever
used herein shall be deemed to mean the Board. The Committee shall, subject to
the provisions of the Plan, have the power to construe this Plan, to determine
all questions hereunder, and to adopt and amend such rules and regulations for
the administration of this Plan as it may deem desirable.

3.   ELIGIBILITY
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          Each member of the Board who is not an employee of the Company or any
of its subsidiaries (a "Non-Employee Director") shall be eligible for the grant
of Options (as hereinafter defined) under this Plan.

4.   AVAILABLE SHARES
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          The total number of shares of Common Stock, par value $.01 per share,
of the Company ("Common Shares"), for which options may be granted under this
Plan shall not exceed 240,000 shares, subject to adjustment as provided in
Section 6 hereof. Shares covered by unexercised Options which are no longer
exercisable for any reason shall be available for issuance under Options granted
hereunder for purposes of computing the foregoing limitation unless the Plan has
been terminated. Shares delivered on exercise of Options may be made available
from authorized and the Treasury of the Company.

5.   OPTIONS
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          (a) Initial Grants. On the date the Company consummates an
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underwritten initial public offering of the Common Stock, each person who is a
Non-Employee Director at the time of approval of this Plan by the Board (the
"Effective Date") shall automatically be
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granted an option ("Option") to purchase 2,500 Common Shares, subject to
adjustment as provided in Section 6 hereof. In addition, each person who first
becomes a Non-Employee Director after the Effective Date shall, on the date such
person becomes a Non-Employee Director, automatically be granted an Option to
purchase 15,000 (post-split, November 22, 1996) Common Shares, subject to
adjustment as provided in Section 6 hereof.

         (b) Annual Grants. On the date of each annual meeting of Stockholders
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of the Company, each person who is a Non-Employee Director shall automatically
be granted an Option to purchase 5,000 (post-split, November 22, 1996) Common
Shares, subject to adjustment as provided in Section 6 hereof.

         (c) Insufficient Shares. Notwithstanding the foregoing, if, on any date
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upon which Options are to be granted under Section 5(a) or 5(b) hereof, the
number of Common Shares remaining available for issuance under this Plan is
insufficient for the grant of Options to purchase the total number of Common
Shares specified in such sections, then each Non-Employee Director entitled to
receive an Option on such date shall be granted an Option to purchase a
proportionate amount of the available number of Common Shares (rounded down to
the greatest number of whole shares). Except for the specific Options referred
to in Sections 5(a) and 5(b) above, no other Options shall be granted under this
Plan.

         (d) Option Price and Terms. Each Option shall be evidenced by a written
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option agreement that shall contain the following terms and provisions:

               (i)    The exercise price per Common Share shall be equal to the
         Fair Market Value (as hereinafter defined) of one Common Share on the
         date of grant of such Option. If, at the time an Option is granted the
         Company's Common Shares are publicly traded, "Fair Market Value" shall
         be determined as of the last business day for which the prices or
         quotes discussed in this sentence are available prior to the date such
         Option is granted and shall mean (i) the average (on that date) of the
         high and low prices of the Common Shares on the principal national
         securities exchange on which the Common Shares are traded, if the
         Common Shares are then listed on a national securities exchange; or
         (ii) the last reported sale price (on that date) of the Common Shares
         on NASDAQ if the Common Shares are not then listed on a national
         securities exchange; or, if not so reported or listed, (iii) the
         closing bid price (or average of bid prices) last quoted (on that date)
         of the Common Shares on the over-the-counter market. If, at the time an
         Option is granted under the Plan, the Company's Common Shares are not
         publicly traded, "Fair Market Value" shall be the fair market value on
         the date the Option is granted as determined by the Committee in good
         faith.

               (ii)   Payment of the exercise price of the Option shall be made
         in full in cash or by check concurrently with the exercise of the
         Option.

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               (iii)  The Option shall be nontransferable by the optionee other
         than by will or the laws of descent and distribution, and shall be
         exercisable during the optionee's life time only by the optionee or the
         optionee's guardian or legal representative.

               (iv)   Options granted pursuant to Section 5(a) shall become
         exercisable by the optionee in three annual installments of 33%, 33%
         and 34% on the first, second and third anniversaries, respectively, of
         the date of grant and shall expire upon the first to occur of the
         following:

                           (A)  the third anniversary of the date upon which the
                      optionee shall cease to be a Non-Employee Director, or

                           (B)   the tenth anniversary of the date of grant.

               (v)    Options granted pursuant to Section 5(b) shall become
         exercisable by the optionee on the first anniversary of the date of
         grant and shall expire upon the first to occur of the following:

                           (A)   the third anniversary of the date upon which
                      the optionee shall cease to be a Non-Employee Director, or

                           (B)   the tenth anniversary of the date of grant.

               (vi)   In the event that the optionee shall cease to be a
         Non-Employee Director prior to the date all or any portion of an Option
         becomes exercisable in accordance with clause (iv) or clause (v) above,
         such Option or portion thereof (A) shall become exercisable in full at
         any time within one year of the date of such event if it occurred as a
         result of the optionee's death or permanent disability, or (B) shall
         terminate in full on the date of such event if it occurred for any
         other reason.

               (vii)  Such other terms and conditions, not inconsistent with the
         terms of this Plan, as the Committee shall include in the written
         option agreement.

               (viii) Notwithstanding the provisions of (iv) and (v) above, all
         options granted hereunder shall become fully exercisable upon a change
         of control. For purposes hereof, a "change of control" shall mean (i)
         the direct or indirect acquisition by any person, entity or group
         acting in concert of more than 35% of the aggregate voting power of the
         outstanding securities of the Company having the right to vote at
         elections of directors,(ii) a majority of the board of directors of the
         Company ceasing to consist of individuals who are members of such board
         on December 19, 1997 or for whose nomination for such membership a
         majority of such members voted in favor, or (iii) the disposition by
         the Company of substantially all its business, other than in connection
         with a mere change of place of incorporation or similar mere change in
         form.

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6.  ADJUSTMENTS
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         (a)   Stock Dividends, Recapitalization, Etc. If the outstanding
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securities of the class then subject to this Plan are increased, decreased or
exchanged for or converted into a different number or kind of securities of the
Company, or if cash, property or securities are distributed in respect of such
outstanding securities, in either case as a result of a reorganization, merger,
consolidation, recapitalization, restructuring, reclassification, dividend
(other than a regular cash dividend) or other distribution, stock split, reverse
stock split or the like, then, unless the terms of such transaction shall
provide otherwise, the Committee shall make appropriate and proportionate
adjustments in (i) the number and type of shares or other securities or cash or
other property that may be acquired pursuant to Options theretofore granted
under this Plan, and (ii) the maximum number and type of shares or other
securities that may be issued pursuant to Options thereafter granted under this
Plan.

         (b)   Merger, Sale of Assets, Etc. If the Company is merged into or
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consolidated with another corporation under circumstances where the Company is
not the surviving corporation or if the Company is liquidated or sells or
otherwise disposes of all or substantially all of its assets while unexercised
Options remain outstanding under the Plan, as of the date thirty (30) days prior
to such transaction (i) all outstanding Options shall become fully vested and
exercisable in full, and (ii) any Options which remain unexercised as of the day
prior to the effective date of the transaction shall be cancelled as of such day
and shall not thereafter be exercisable by anyone; provided that the accelerated
exercisability of Options shall be contingent on completion of the transaction
and shall be null and void if the transaction is not consummated; and provided,
further, that accelerated exercisability pursuant to this provision shall not
extend the expiration date for any Option determined pursuant to Section 5.

7.  AMENDMENT AND TERMINATION OF PLAN
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         The Board may amend or terminate this Plan at any time and in any
manner, subject to the following:

         (a) no such amendment or termination shall deprive the recipient of any
Option theretofore granted under this Plan, without the consent of such
recipient, of any of his or her rights thereunder or with respect thereto; and

         (b) Section 5 hereof shall not be amended more than once every six
months other than to comport with changes in the Internal Revenue Code, the
Employee Retirement Income Security Act of 1974, or the rules thereunder.

8.  EFFECTIVE DATE AND DURATION OF PLAN
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         This Plan shall become effective and shall be deemed to have been
adopted on October 22, 1993, the date the Plan was adopted by the Board. The
stockholders of the

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Company approved the Plan on January 13, 1994. This Plan shall terminate and no
Options shall be granted hereunder after October 22, 2003.


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         Amended by the Board of Directors on March 8, 1996, with the approval
of the stockholders on May 3, 1996.
         Amended by the Board of Directors on December 19, 1997, with the
approval of the stockholders on April 16, 1998.
         Amended by the Board of Directors on March 12, 1999, with the approval
of the stockholders on April 30, 1999.

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