Document:

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                                                                    Exhibit 10.1

                       NATURAL MICROSYSTEMS CORPORATION

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

                               _________________

1.   PURPOSE
     -------

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

          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
     -----------

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

          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
     -------

          (a) Initial Grants. On the date the Company consummates an
              --------------
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
             -------------
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
             -------------------
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
             ----------------------
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
               --------------------------------------
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
               ---------------------------
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
    ---------------------------------

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

         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.

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

         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.

                                      -5-<PAGE>

                                                                    EXHIBIT 10.2

                       NATURAL MICROSYSTEMS CORPORATION
                       1993 EMPLOYEE STOCK PURCHASE PLAN
              (As Amended and Restated Effective March 12, 1999)

     l.  PURPOSE.  The purpose of this Employee Stock Purchase Plan (the "Plan")
         -------
is to provide employees of Natural MicroSystems Corporation, a Delaware
corporation (the "Company"), and its subsidiaries, an opportunity to purchase
Common Stock, $.01 par value, of the Company (the "Shares").  The Plan is
intended to qualify as an "employee stock purchase plan" within the meaning of
Section 423 of the Internal Revenue Code of 1986, as amended (the "Code").

     2.  ADMINISTRATION OF THE PLAN.  The Board of Directors or any committee or
         --------------------------
persons to whom it delegates its authority (the "Administrator") shall
administer, interpret and apply all provisions of the Plan.  The Administrator
may waive such provisions of the Plan as it deems necessary to meet special
circumstances not anticipated or covered expressly by the Plan.  Nothing
contained in this Section shall be deemed to authorize the Administrator to
alter or administer the provisions of the Plan in a manner inconsistent with the
provisions of Section 423 of the Code.  No member of the Administrator shall be
liable for any action or determination made in good faith with respect to the
Plan or any right granted under it.

     3.  ELIGIBLE EMPLOYEES.  Subject to the provisions of Sections 8, 9 and 10
         ------------------
below, any individual who is in the full-time employment (as defined below) of
the Company, or any of its subsidiaries (as defined in Section 424(f) of the
Code) the employees of which are designated by the Board of Directors as
eligible to participate in the Plan, is eligible to participate in any Offering
of Shares (as defined in Section 4 below) made by the Company hereunder.  Full-
time employment shall include all employees whose customary employment is:  (a)
in excess of 20 hours per week; and (b) more than five months in the relevant
calendar year.

     4.  OFFERING DATES.  From time to time the Company, by action of the Board
         --------------
of Directors, will grant rights to purchase Shares to employees eligible to
participate in the Plan pursuant to one or more offerings (each of which is an
"Offering") on a date or series of dates (each of which is an "Offering Date")
designated for this purpose by the Board of Directors.

     5.  PRICES.  The price per share for each grant of rights hereunder shall
         ------
be the lesser of: (a) eighty-five percent (85%) of the fair market value of a
Share on the Offering Date on which such right was granted; or (b) eighty-five
percent (85%) of the fair market value of a Share on the date such right is
exercised. At its discretion, the Board of Directors may determine a higher
price for a grant of rights. For purposes of this Plan, the term "fair market
value" on any date means shall mean (i) the average (on that date) of the high
and low prices for shares of the Common Stock on the principal national
securities exchange on which the Common Stock are traded, if the Common Stock is
then listed on a national securities exchange; or (ii) the last reported sale
price (on that date) of shares of the Common Stock on NASDAQ if the Common Stock
is not then listed on a national securities exchange; or, if not so reported or
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listed, (iii) the closing bid price (or average of bid prices) last quoted (on
that date) of shares of the Common Stock on the over-the-counter market. If the
Company's Common Stock is not publicly traded at the time a right is granted
under this Plan, "fair market value" shall mean the fair market value of shares
of the Common Stock as determined by the Administrator after taking into
consideration all factors which it deems appropriate, including, without
limitation, recent sale and offer prices of shares of the Common Stock in
private transactions negotiated at arm's length.

     6.  EXERCISE OF RIGHTS AND METHOD OF PAYMENT.  (a)  Rights granted under
         ----------------------------------------
the Plan will be exercisable periodically on specified dates as determined by
the Board of Directors.

         (b)  The method of payment for Shares purchased upon exercise of
rights granted hereunder shall be through regular payroll deductions or by lump
sum cash payment, or both, as determined by the Board of Directors.  No interest
shall be paid upon payroll deductions unless specifically provided for by the
Board of Directors.

         (c)  Any payments received by the Company from a participating
employee and not utilized for the purchase of Shares upon exercise of a right
granted hereunder shall be promptly returned to such employee by the Company
after termination of the right to which the payment relates.

     7.  TERM OF RIGHTS.  Rights granted on any Offering Date shall be
         --------------
exercisable upon the expiration of such period ("Offering Period") as shall be
determined by the Board of Directors when it authorizes the Offering, provided
that such Offering Period shall in no event be longer than twenty-seven (27)
months.

     8.  SHARES COVERED BY THE PLAN.  No more than 700,000 Shares may be sold
         --------------------------
pursuant to rights granted under the Plan; provided, however, that appropriate
adjustment shall be made in such number, in the number of Shares covered by
outstanding rights granted hereunder, in the exercise price of the rights and in
the maximum number of Shares which an employee may purchase (pursuant to Section
9 below) to give effect to any mergers, consolidations, reorganizations,
recapitalizations, stock splits, stock dividends or other relevant changes in
the capitalization of the Company occurring after the effective date of the
Plan, provided that no fractional Shares shall be subject to a right and each
right shall be adjusted downward to the nearest full Share.  Any agreement of
merger or consolidation will include provisions for protection of the then
existing rights of participating employees under the Plan.  Either authorized
and unissued Shares or issued Shares heretofore or hereafter reacquired by the
Company may be made subject to rights under the Plan.  If for any reason any
right under the Plan terminates in whole or in part, Shares subject to such
terminated right may again be subjected to a right under the Plan.

     9.  LIMITATIONS ON GRANTS.  (a)  No employee shall be granted a right
         ---------------------
hereunder if such employee, immediately after the right is granted, would own
stock or rights to

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purchase stock possessing five percent (5%) or more of the total combined voting
power or value of all classes of stock of the Company, or of any subsidiary,
computed in accordance with Sections 423(b)(3) and 424(d) of the Code.

          (b) No employee shall be granted a right which permits his right to
purchase shares under all employee stock purchase plans of the Company and its
subsidiaries to accrue at a rate which exceeds twenty-five thousand dollars
($25,000) (or such other maximum as may be prescribed from time to time by the
Code) of the fair market value of such Shares (determined at the time such right
is granted) for each calendar year in which such right is outstanding at any
time in accordance with the provisions of Section 423(b)(8) of the Code.

          (c) No right granted to any participating employee under a single
Offering shall cover more shares than may be purchased at an exercise price
equal to 10% of the compensation payable to the employee during the Offering not
taking into consideration any changes in the employee's rate of compensation
after the date the employee elects to participate in the Offering, or such other
percentage as determined by the Board of Directors from time to time.

     10.  LIMIT ON PARTICIPATION.  Participation in an Offering shall be limited
          ----------------------
to eligible employees who elect to participate in such Offering in the manner,
and within the time limitation, established by the Board of Directors when it
authorizes the offering.

     11.  CANCELLATION OF ELECTION TO PARTICIPATE.  An employee who has elected
          ---------------------------------------
to participate in an Offering may, unless the employee has waived this
cancellation right at the time of such election in a manner established by the
Board of Directors, cancel such election as to all (but not part) of the rights
granted under such Offering by giving written notice of such cancellation to the
Company before the expiration of the Offering Period.  Any amounts paid by the
employee for the Shares or withheld for the purchase of Shares from the
employee's compensation through payroll deductions shall be paid to the
employee, without interest, upon such cancellation.

     12.  TERMINATION OF EMPLOYMENT.  Upon termination of employment for any
          -------------------------
reason, including the death of the employee, before the date on which any rights
granted under the Plan are exercisable, all such rights shall immediately
terminate and amounts paid by the employee for the Shares or withheld for the
purchase of Shares from the employee's compensation through payroll deductions
shall be paid to the employee or to the employee's estate, without interest.

     13.  EMPLOYEE'S RIGHTS AS STOCKHOLDER.  No participating employee shall
          --------------------------------
have any rights as a stockholder in the Shares covered by a right granted
hereunder until such right has been exercised, full payment has been made for
the corresponding Shares and the Share certificate is actually issued.

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     14.  RIGHTS NOT TRANSFERABLE.  Rights under the Plan are not assignable or
          -----------------------
transferable by a participating employee and are exercisable only by the
employee.

     15.  LIMITS ON SALE OF STOCK PURCHASED UNDER THE PLAN.  The Plan is
          ------------------------------------------------
intended to provide shares of Common Stock for investment and not for resale.
The Company does not, however, intend to restrict or influence any employee in
the conduct of his/her own affairs.  An employee may, therefore, sell stock
purchased under the Plan at any time the employee chooses, subject to compliance
with any applicable Federal or state securities laws; provided, however, that
because of certain Federal tax requirements, each employee agrees by entering
the Plan, promptly to give the Company notice of any such stock disposed of
within two years after the date of grant of the applicable right showing the
number of such shares disposed of.  THE EMPLOYEE ASSUMES THE RISK OF ANY MARKET
FLUCTUATIONS IN THE PRICE OF THE STOCK.

     16.  AMENDMENTS TO OR DISCONTINUANCE OF THE PLAN.  The Board of Directors
          -------------------------------------------
may at any time terminate or amend this Plan without notice and without further
action on the part of stockholders of the Company, provided that no such
termination or amendment shall adversely affect the then existing rights of any
participating employee.

     17.  EFFECTIVE DATE AND APPROVALS.  The Plan is being adopted by the Board
          ----------------------------
of Directors on October 22, 1993 to become effective as of said date. The Plan
was  approved by the stockholders on January 13, 1994.  The Company's obligation
to offer, sell and deliver its Shares under the Plan is subject to the approval
of any governmental authority required in connection with the authorized
issuance or sale of such Shares and is further subject to the Company receiving
the opinion of its counsel that all applicable securities laws have been
complied with.

     18.  TERM OF PLAN.  No rights shall be granted under the Plan after October
          ------------
22, 2003.

                        ______________________________

     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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