1
                                                                   EXHIBIT 10.18

                              VOICETEK CORPORATION

                             1996 STOCK OPTION PLAN
                      FOR NON-EMPLOYEE DIRECTORS AND CLERK

       1. PURPOSE

       The purpose of this Voicetek Corporation 1996 Stock Option Plan for
Non-Employee Directors (the "Plan") is to attract and retain the services of
experienced and knowledgeable independent directors who are not employees
(sometimes referred to herein collectively as "Participants") of Voicetek
Corporation ("Voicetek") for the benefit of Voicetek and its stockholders and to
provide additional incentive for such Participants to continue to work in the
best interests of Voicetek and its stockholders through continuing ownership of
its common stock.

       2. SHARES SUBJECT TO THE PLAN

       The total number of shares of common stock, par value $.01 per share
("Shares"), of Voicetek for which options may be granted under the Plan shall
not exceed 90,000 in the aggregate, subject to adjustment in accordance with
Section 9 hereof.
 
       3. ELIGIBILITY; GRANT OF OPTION

       Each of John Blaeser, Christopher Lynch, Alan Voulgaris and Sherman Wolf,
who are the four current directors of Voicetek who are not otherwise employees
of Voicetek or any subsidiary, and upon their election to the Board of Directors
of Voicetek (the "Board"), all new non-employee directors duly elected in the
five year period commencing on the date of the adoption of the Plan, shall be
granted an option to acquire twelve thousand (12,000) Shares under the Plan. In
addition, Anthony J. Medaglia, Jr., the Clerk of the Corporation, shall be
granted an option to acquire ten thousand (10,000) Shares under the Plan. The
date of grant for such options
   2
granted to the Clerk and four current non-employee directors named above shall
be the date of adoption of the Plan by the Board, but such options shall become
effective as of such date of grant only upon shareholder approval of this Plan
in accordance with Section 13 hereof. The options shall be non-qualified options
not intended to meet the requirements of Section 422 of the Internal Revenue
Code of 1986, as amended (the "Code"). The date of grant for each subsequently
elected non-employee director shall be the date of election.

       4. OPTION AGREEMENT

       Each option granted under the Plan shall be evidenced by an option
agreement (the "Agreement") duly executed on behalf of Voicetek and by the Clerk
or the director to whom such option is granted, which Agreements shall (i)
comply with and be subject to the terms and conditions of the Plan and (ii)
provide that the optionee agrees to continue to serve as the Clerk or a director
of Voicetek, as the case may be, during the term for which he was elected.

       5. OPTION EXERCISE PRICE

       Subject to the provisions of Section 9 hereof, the option exercise price
for the options granted to the Clerk and four current non-employee directors
named above under the Plan shall be $5.00. Subject to the provisions of Section
9 hereof, the option exercise price for options granted to any subsequently
elected clerk or non-employee director under the Plan shall be the fair market
value of the Shares of the common stock of Voicetek covered by the option on the
date of grant of the option. For the purposes of this Section 5 and of Section
6(b) herein, the fair market value of the common stock of Voicetek shall be the
mean between the high and low sales prices of the common stock of Voicetek on
the NASDAQ National Market System as reported in the Wall Street Journal on the
date of grant for the immediately preceding business day; provided

                                        2
   3
that if the common stock of Voicetek is not listed on or actually trading on the
NASDAQ National Market System, fair market value shall be determined in good
faith by the Board.

       6. TIME AND MANNER OF EXERCISE OF OPTION

       (a) Options granted under the Plan shall, subject to the provisions of
Section 7, become exercisable in equal increments on the first, second and third
anniversaries of the date at the grant of such options; provided, however, that
no option granted under the Plan may be exercised prior to approval of the Plan
by the stockholders of Voicetek.

       (b) To the extent that the right to exercise an option has accrued and is
in effect, the option may be exercised in full at one time or in part from time
to time by giving written notice to Voicetek, signed by the person or persons
exercising the option, stating the number of Shares with respect to which the
option is being exercised, accompanied by payment in full for such Shares, which
payment may be in cash or in whole or in part in Shares of the common stock of
Voicetek already owned for a period of at least six months by the person or
persons exercising the option, valued at fair market value, as determined under
Section 5 hereof, on the date of exercise; provided, however, that there shall
be no such exercise at any one time as to fewer than one hundred (100) Shares
or all of the remaining Shares then purchasable by the person or persons
exercising the option, if fewer than one hundred (100) Shares. Upon such
exercise, delivery of a certificate for paid-up non-assessable Shares shall be
made at the principal Massachusetts office of Voicetek to the person or persons
exercising the option at such time, during ordinary business hours, not more
than thirty (30) days from the date of receipt of the notice by Voicetek, as
shall be designated in such notice, or at such time, place and manner as may be
agreed upon by Voicetek and the person or persons exercising the option.

                                        3
   4
       7. TERM OF OPTIONS

       (a) Each option shall expire ten (10) years from the date of the granting
thereof, but shall be subject to earlier termination as herein provided.

       (b) In the event of the death of an optionee, the option granted to such
optionee may be exercised, to the extent the optionee was entitled to do so on
the date of such optionee's death, by the estate of such optionee or by any
person or persons who acquired the right to exercise such option by bequest or
inheritance or otherwise by reason of the death of such optionee. Such option
may be exercised at any time within one (1) year after the date of death of such
optionee, at which time the option shall terminate, or prior to the date on
which the option otherwise expires by its terms, whichever is earlier.

       (c) In the event that an optionee ceases to be the Clerk or a director of
Voicetek, as the case may be, the option granted to such optionee may be
exercised by him, but only to the extent that under Section 6 hereof the right
to exercise the option has accrued and is in effect on the date that the
optionee ceases to be the Clerk or a director, as the case may be. Such option
may be exercised at any time within seven (7) business days after the date such
optionee ceases to be a director of Voicetek, as the case may be, at which time
the option shall terminate, but in any event prior to the date on which the
option expires by its terms, whichever is earlier, unless termination as a
director (a) was by Voicetek for cause, in which case the option shall terminate
immediately at the time the optionee ceases to be a director of Voicetek, (b)
was because the optionee has become disabled (within the meaning of Section
22(e)(3) of the Code), or (c) was by reason of the death of the optionee. In the
case of death, see Section 7(b) above. In the case of disability, the option may
be exercised, to the extent exercisable under Section 6 hereof when

                                        4
   5
the optionee ceased to be a director, at any time within one (1) year after the
date of termination of the optionee's directorship with Voicetek, at which time
the option shall terminate, but in any event prior to the date on which the
option otherwise expires by its terms, whichever is earlier.

       8. OPTIONS NOT TRANSFERABLE

       The right of any optionee to exercise an option granted to him under the
Plan shall not be assignable or transferable by such optionee otherwise than by
will or the laws of descent and distribution, or pursuant to a qualified
domestic relations order as defined by the Code or Title I of the Employee
Retirement Income Security Act, or the rules thereunder. Any option granted
under the Plan shall be exercisable during the lifetime of such optionee only by
him. Any option granted under the Plan shall be null and void and without effect
upon the bankruptcy of the optionee, or upon any attempted assignment or
transfer, except as herein provided, including without limitation any purported
assignment, whether voluntary or by operation of law, pledge, hypothecation or
other disposition, attachment, trustee process or similar process, whether legal
or equitable, upon such option.

       9. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION

       In the event that the outstanding Shares of the common stock of Voicetek
are changed into or exchanged for a different number or kind of shares or other
securities of Voicetek or of another corporation by reason of any
reorganization, merger, consolidation, recapitalization, reclassification, stock
split-up, combination of shares or dividends payable in capital stock,
appropriate adjustment shall be made in the number and kind of shares as to
which outstanding options, or portions thereof then unexercised, shall be
exercisable, to the end that the proportionate interest of the optionee shall be
maintained as before the occurrence of such event,

                                        5
   6
and such adjustment in outstanding options shall be made without change in the
total price applicable to the unexercised portion of such options and with a
corresponding adjustment in the option price per share.

       10. RESTRICTIONS ON ISSUE OF SHARES

       Notwithstanding the provisions of Section 6 hereof, Voicetek may delay
the issuance of Shares covered by the exercise of any option and the delivery of
a certificate for such Shares until one of the following conditions shall be
satisfied:

             (i) the Shares with respect to which an option has been exercised
are at the time of the issue of such Shares effectively registered under
applicable Federal and state securities acts now in force or hereafter amended;
or

             (ii) counsel for Voicetek shall have given an opinion, which
opinion shall not be unreasonably conditioned or withheld, that such Shares are
exempt from registration under applicable Federal and state securities acts now
in force or hereafter amended.

       It is intended that all exercises of options shall be effective.
Accordingly, Voicetek shall use its best efforts to bring about compliance with
the above conditions within a reasonable time, except that Voicetek shall be
under no obligation to cause a registration statement or a post-effective
amendment to any registration statement to be prepared at its expense solely for
the purpose of covering the issue of Shares in respect of which any option may
be exercised, except as otherwise agreed to by Voicetek in writing.

                                        6
   7
    11. RIGHTS OF HOLDER ON PURCHASE FOR INVESTMENT; SUBSEQUENT REGISTRATION

    Unless the Shares to be issued upon exercise of an option granted under the
Plan have been effectively registered under the Securities Act of 1933, as now
in force or hereafter amended, Voicetek shall be under no obligation to issue
any Shares covered by any option unless the person who exercises such option, in
whole or in part, shall give a written representation and undertaking to
Voicetek which is satisfactory in form and scope to counsel to Voicetek and upon
which, in the opinion of such counsel, Voicetek may reasonably rely, that he is
acquiring the Shares issued to him pursuant to such exercise of the option for
his own account as an investment and not with a view to, or for sale in
connection with, the distribution of any such Shares, and that he will make no
transfer of the same except in compliance with any rules and regulations in
force at the time of such transfer under the Securities Act of 1933, or any
other applicable law, and that if Shares are issued without such registration a
legend to this effect may be endorsed upon the securities so issued. In the
event that Voicetek shall, nevertheless, deem it necessary or desirable to
register under the Securities Act of 1933 or other applicable statutes any
Shares with respect to which an option shall have been exercised, or to qualify
any such Shares for exemption from the Securities Act of 1933 or other
applicable statutes, then Voicetek shall take such action at its own expense and
may require from each optionee such information in writing for use in any
registration statement, prospectus, preliminary prospectus or offering circular
as is reasonably necessary for such purpose and may require reasonable indemnity
to Voicetek and its officers and directors from such holder against all losses,
claims, damages and liabilities arising from such use of the information so
furnished and caused by any untrue statement of any material fact

                                        7
   8
therein or caused by the omission to state a material fact required to be stated
therein or necessary to make the statements therein not misleading in light of
the circumstances under which they were made.

    12. LOANS PROHIBITED

    Voicetek shall not, directly or indirectly, lend money to an optionee or to
any person or persons entitled to exercise an option by reason of the death of
an optionee for the purpose of assisting him or them in the acquisition of
Shares covered by an option granted under the Plan.

    13. APPROVAL OF STOCKHOLDERS

    The Plan shall be subject to approval by the affirmative vote of the holders
of a majority of the securities of Voicetek present or represented and entitled
to vote at a duly held stockholders' meeting, or by written consent of all of
the stockholders, and shall take effect immediately as of its date of adoption
upon such approval.

    14. EXPENSES OF THE PLAN

    All costs and expenses of the adoption and administration of the Plan shall
be borne by Voicetek, and none of such expenses shall be charged to any
optionee.

    15. TERMINATION AND AMENDMENT OF PLAN

    Unless sooner terminated as herein provided, the Plan shall terminate ten
(10) years from the date upon which the Plan was duly approved by the
stockholders. The Board may at any time terminate the Plan or make such
modification or amendment thereof as it deems advisable; provided, however,
that, except as provided in Section 9 hereof, no modification or amendment to
the provisions of the Plan may be made more than once every six (6) months other
than to comport with changes in the Code, the Employee Retirement Income
Security Act, or the rules

                                        8
   9
thereunder, if the effect of such amendment or modification would be to change
(i) the requirements for eligibility under the Plan, (ii) the timing of the
grants of options to be granted under the Plan or the exercise price or vesting
schedule thereof, or (iii) the number of Shares subject to options to be granted
under the Plan either in the aggregate or to the Clerk or one director. Any
amendment to the provisions of the Plan which (i) materially increases the
number of Shares which may be subject to options granted under the Plan, (ii)
materially increases the benefits accruing to Participants under the Plan, or
(iii) materially modifies the requirement for eligibility to participate in the
Plan, shall be subject to approval by the stockholders of Voicetek obtained in
the manner stated in Section 13 hereof. Termination or any modification or
amendment of the Plan shall not, without the consent of an optionee, affect his
rights under an option previously granted to him.

    16. LIMITATION OF RIGHTS IN THE OPTION SHARES

    An optionee shall not be deemed for any purpose to be a stockholder of
Voicetek with respect to any of the options except to the extent that the option
shall have been exercised with respect thereto and, in addition, a certificate
shall have been issued theretofore and delivered to the optionee.

    17. NOTICES

    Any communication or notice required or permitted to be given under the Plan
shall be in writing, and mailed by registered or certified mail or delivered by
hand, if to Voicetek, to its principal place of business, Attention: President,
and, if to an optionee, to the address as appearing on the records of Voicetek.

                                        9
   10
    18. COMPLIANCE WITH RULE 16b-3.

    It is the intention of Voicetek that the Plan comply in all respects with
Rule 16b-3 promulgated under Section 16(b) of the Securities Exchange Act of
1934 (the "Act") and that Participants remain disinterested persons for purposes
of administering other employee benefit plans of Voicetek and having
transactions under such other plans be exempt from Section 16(b) of the Act.
Therefore, if any Plan provision is found not to be in compliance with Rule
16b-3 or if any Plan provisions would disqualify Participants from remaining
disinterested persons, that provisions shall be deemed null and void, and in all
events the Plan shall be construed in favor of its meeting the requirements of
Rule 16b-3.

APPROVED BY THE BOARD OF DIRECTORS:  AUGUST 1, 1996


APPROVED BY THE STOCKHOLDERS:  ________________________________________

                                       10