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                                                                  Exhibit 10.21

                                BROOKTROUT, INC.

                          EXECUTIVE RETENTION AGREEMENT

        This Executive Retention Agreement, by and between Brooktrout, Inc., a
Massachusetts corporation (the "Company"), and R. Andrew O'Brien (the
"Executive") is made as of March 16, 2005 (the "Effective Date").

        WHEREAS, the Company recognizes that, as is the case with many
publicly-held corporations, the possibility of a change in control of the
Company exists and that such possibility, and the uncertainty and questions that
it may raise among key personnel, may result in the departure or distraction of
key personnel to the detriment of the Company and its stockholders; and

        WHEREAS, the Board of Directors of the Company (the "Board") has
determined that appropriate steps should be taken to reinforce and encourage the
continued employment and dedication of certain of the Company's key personnel
without distraction from the possibility of a change in control of the Company
and related events and circumstances;

        NOW, THEREFORE, as an inducement for and in consideration of the
Executive remaining in its employ, the Company agrees that the Executive shall
receive the severance benefits set forth in this Agreement in the event the
Executive's employment with the Company is terminated under the circumstances
described below subsequent to a Change in Control (as defined in Section 1.1).

        1. KEY DEFINITIONS.

        As used herein, the following terms shall have the following respective
meanings:

                1.1.    "CHANGE IN CONTROL" means an event or occurrence set
        forth in any one or more of subsections (a) through (e) below (including
        an event or occurrence that constitutes a Change in Control under one of
        such subsections but is specifically exempted from another such
        subsection):

                        (a)  the acquisition by an individual, entity or group
                             (within the meaning of Section 13(d)(3) or 14(d)(2)
                             of the Securities Exchange Act of 1934, as amended
                             (the "Exchange Act")) (a "Person") of beneficial
                             ownership of any capital stock of the Company if,
                             after such acquisition, such Person beneficially
                             owns (within the meaning of Rule 13d-3 promulgated
                             under the Exchange Act) at least 25%, but less than
                             35%, of either (x) the then-outstanding shares of
                             common stock of the Company (the "Outstanding
                             Company Common Stock") or (y) the combined voting
                             power of the then-outstanding securities of the
                             Company entitled to vote generally in the election
                             of directors (the "Outstanding Company Voting
                             Securities"); PROVIDED, HOWEVER, that for purposes
                             of this subsection (a), the following acquisitions
                             shall not constitute a Change in Control:

                             (i)   any acquisition directly from the Company
                                   (excluding an acquisition pursuant to the
                                   exercise, conversion or exchange of any
                                   security exercisable for, convertible into or
                                   exchangeable for common stock or voting
                                   securities of the Company, unless the Person
                                   exercising, converting or exchanging such
                                   security acquired such security directly from
                                   the Company or an underwriter or agent of the
                                   Company),

                             (ii)  any acquisition by the Company,

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                             (iii) any acquisition by any employee benefit plan
                                   (or related trust) sponsored or maintained by
                                   the Company or any corporation controlled by
                                   the Company, or

                             (iv)  any acquisition by any corporation pursuant
                                   to a transaction that complies with clauses
                                   (i) and (ii) of subsection (d) of this
                                   Section 1.1;

                        (b)  the acquisition by a Person of beneficial ownership
                             of any capital stock of the Company if, after such
                             acquisition, such Person beneficially owns (within
                             the meaning of Rule 13d-3 promulgated under the
                             Exchange Act) 35% or more of either (x) the
                             Outstanding Company Common Stock or (y) the
                             Outstanding Company Voting Securities;

                        (c)  such time as the Continuing Directors do not
                             constitute a majority of the Board (or, if
                             applicable, the board of directors of a successor
                             corporation to the Company), where the term
                             "Continuing Director" means at any date a member of
                             the Board:

                             (i)   who was a member of the Board on the date of
                                   the execution of this Agreement or;

                             (ii)  who was nominated or elected subsequent to
                                   such date by at least a majority of the
                                   directors who were Continuing Directors at
                                   the time of such nomination or election or
                                   whose election to the Board was recommended
                                   or endorsed by at least a majority of the
                                   directors who were Continuing Directors at
                                   the time of such nomination or election;
                                   PROVIDED, HOWEVER, that there shall be
                                   excluded from this clause (ii) any individual
                                   whose initial assumption of office occurred
                                   as a result of an actual or threatened
                                   election contest with respect to the election
                                   or removal of directors or other actual or
                                   threatened solicitation of proxies or
                                   consents, by or on behalf of a person other
                                   than the Board;

                        (d)  the consummation of a merger, consolidation,
                             reorganization, recapitalization or statutory share
                             exchange involving the Company or a sale or other
                             disposition of all or substantially all of the
                             assets of the Company in one or a series of
                             transactions (a "Business Combination"), unless,
                             immediately following such Business Combination,
                             each of the following two conditions is satisfied:

                             (i)   all or substantially all of the individuals
                                   and entities who were the beneficial owners
                                   of the Outstanding Company Common Stock and
                                   Outstanding Company Voting Securities
                                   immediately prior to such Business
                                   Combination beneficially own, directly or
                                   indirectly, more than 50% of the
                                   then-outstanding shares of common stock and
                                   the combined voting power of the
                                   then-outstanding securities entitled to vote
                                   generally in the election of directors,
                                   respectively, of the resulting or acquiring
                                   corporation in such Business Combination
                                   (which shall include a corporation that as a
                                   result of such transaction owns the Company
                                   or substantially all of the Company's assets
                                   either directly or through one or more
                                   subsidiaries) (such resulting or acquiring
                                   corporation is referred to herein as the
                                   "Acquiring Corporation") in substantially the
                                   same proportions as their ownership,
                                   immediately prior to such Business
                                   Combination, of the Outstanding Company
                                   Common Stock and Outstanding Company Voting
                                   Securities, respectively; and

                             (ii)  no Person (excluding any employee benefit
                                   plan (or related trust) maintained or
                                   sponsored by the Company or by the Acquiring
                                   Corporation) beneficially

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                                   owns, directly or indirectly, 25% or more of
                                   the then outstanding shares of common stock
                                   of the Acquiring Corporation, or of the
                                   combined voting power of the then-outstanding
                                   securities of such corporation entitled to
                                   vote generally in the election of directors
                                   (except to the extent that such ownership
                                   existed prior to the Business Combination);
                                   or

                        (e)  approval by the stockholders of the Company of a
                             complete liquidation or dissolution of the Company.

                1.2.    "CHANGE IN CONTROL DATE" means the first date during the
        Term (as defined in Section 2) on which a Change in Control occurs.
        Anything in this Agreement to the contrary notwithstanding, if:

                        (a)  a Change in Control occurs,

                        (b)  the Executive's employment with the Company is
                             terminated prior to the date on which the Change in
                             Control occurs, and

                        (c)  it is reasonably demonstrated by the Executive that
                             such termination of employment (i) was at the
                             request of a third party who has taken steps
                             reasonably calculated to effect a Change in Control
                             or (ii) otherwise arose in connection with or in
                             anticipation of a Change in Control,

        then for all purposes of this Agreement the "Change in Control Date"
        shall mean the date immediately prior to the date of such termination of
        employment.

                1.3.    "CAUSE" means:

                        (a)  the Executive's willful and continued failure to
                             substantially perform the Executive's reasonable
                             assigned duties as an officer of the Company (other
                             than any such failure resulting from incapacity due
                             to physical or mental illness or any failure after
                             the Executive gives notice of termination for Good
                             Reason), which failure is not cured within 30 days
                             after a written demand for substantial performance
                             is received by the Executive from the Board that
                             specifically identifies the manner in which the
                             Board believes the Executive has not substantially
                             performed the Executive's duties; or

                        (b)  the Executive's willful engagement in illegal
                             conduct or gross misconduct that is materially and
                             demonstrably injurious to the Company.

        For purposes of this Section 1.3, no act or failure to act by the
        Executive shall be considered "willful" unless it is done, or omitted to
        be done, in bad faith and without reasonable belief that the Executive's
        action or omission was in the best interests of the Company.

                1.4.    "GOOD REASON" means the occurrence, without the
        Executive's written consent, of any of the following events or
        circumstances:

                        (a)  the assignment to the Executive of duties that are
                             inconsistent in any material respect with the
                             Executive's position (including status, offices,
                             titles and reporting requirements), authority or
                             responsibilities in effect immediately prior to the
                             earliest to occur of:

                             (i)   the Change in Control Date,

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                             (ii)  the date of the execution by the Company of
                                   the initial written agreement or instrument
                                   providing for the Change in Control, and

                             (iii) the date of the adoption by the Board of
                                   Directors of a resolution providing for the
                                   Change in Control (with the earliest to occur
                                   of such dates referred to herein as the
                                   "Measurement Date"),

                             or any other action or omission by the Company that
                             results in a material diminution in such position,
                             authority or responsibilities;

                        (b)  a reduction in the Executive's annual base salary
                             as in effect on the Measurement Date or as the same
                             was or may be increased thereafter from time to
                             time;

                        (c)  the failure by the Company to:

                             (i)   continue in effect any material compensation
                                   or benefit plan or program (including any
                                   life insurance, medical, health and accident
                                   or disability plan and any vacation or
                                   automobile program or policy) (a "Benefit
                                   Plan") in which the Executive participates or
                                   that is applicable to the Executive
                                   immediately prior to the Measurement Date,
                                   unless an equitable arrangement (embodied in
                                   an ongoing substitute or alternative plan)
                                   has been made with respect to such plan or
                                   program,

                             (ii)  continue the Executive's participation
                                   therein (or in such substitute or alternative
                                   plan) on a basis not materially less
                                   favorable, both in terms of the amount of
                                   benefits provided and the level of the
                                   Executive's participation relative to other
                                   participants, than the basis existing
                                   immediately prior to the Measurement Date, or

                             (iii) award cash bonuses to the Executive in
                                   amounts and in a manner substantially
                                   consistent with past practice in light of the
                                   Company's financial performance;

                        (d)  a change by the Company in the location at which
                             the Executive performs the Executive's principal
                             duties for the Company to a new location that is
                             both:

                             (i)   outside a radius of 35 miles from the
                                   Executive's principal residence immediately
                                   prior to the Measurement Date, and

                             (ii)  more than 20 miles from the location at which
                                   the Executive performed the Executive's
                                   principal duties for the Company immediately
                                   prior to the Measurement Date,

                             or a requirement by the Company that the Executive
                             travel on Company business to a substantially
                             greater extent than required immediately prior to
                             the Measurement Date;

                        (e)  the failure of the Company to obtain the agreement
                             from any successor to the Company to assume and
                             agree to perform this Agreement, as required by
                             Section 6.1;

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                        (f)  any failure of the Company to pay or provide to the
                             Executive any portion of the Executive's
                             compensation or benefits due under any Benefit Plan
                             within seven days of the date such compensation or
                             benefits are due; or

                        (g)  any material breach by the Company of this
                             Agreement or any employment agreement with the
                             Executive.

        Notwithstanding the occurrence of any such event or circumstance, such
        occurrence shall not be deemed to constitute Good Reason if, prior to
        the Date of Termination specified in the Notice of Termination (each as
        defined in Section 3.2(a)) given by the Executive in respect thereof,
        such event or circumstance has been fully corrected and the Executive
        has been reasonably compensated for any losses or damages resulting
        therefrom, PROVIDED that such right of correction by the Company shall
        only apply to the first Notice of Termination for Good Reason given by
        the Executive. For purposes of this Agreement, any good faith
        determination of "Good Reason" made by the Executive shall be
        conclusive, binding and final. The Executive's right to terminate the
        Executive's employment for Good Reason shall not be affected by the
        Executive's incapacity due to physical or mental illness.

                1.5.    "DISABILITY" means the Executive's absence from the
        full-time performance of the Executive's duties with the Company for 180
        consecutive calendar days as a result of incapacity due to mental or
        physical illness that is determined to be total and permanent by a
        physician selected by the Company or its insurers and acceptable to the
        Executive or the Executive's legal representative.

                1.6.    "QUALIFYING OPTION" means an outstanding stock option
        agreement granted, either before or after the date hereof, to the
        Executive under any stock option or incentive plan of the Company,
        whether in existence on the date hereof or adopted by the Company after
        the date hereof, which agreement provides (either by its terms or by
        incorporation from such plan) for the acceleration of vesting, in whole
        or in part, upon a change-in-control, sale or similar event, as defined
        for purposes thereof (with respect to such Qualifying Option, a
        "QUALIFYING OPTION EVENT"), regardless of whether such Qualifying Option
        Event constitutes a Change in Control.

        2. TERM OF AGREEMENT.

        This Agreement, and all rights and obligations of the parties hereunder,
shall take effect upon the Effective Date and shall expire upon the first to
occur of:

        (a)     the expiration of the Term (as defined below) if a Change in
                Control has not occurred during the Term,

        (b)     the termination of the Executive's employment with the Company
                prior to the Change in Control Date,

        (c)     the date 12 months after the Change in Control Date, if the
                Executive is still employed by the Company as of such later
                date, or

        (d)     the fulfillment by the Company of all of its obligations under
                Sections 4 and 5.2 if the Executive's employment with the
                Company terminates within 12 months following the Change in
                Control Date.

"Term" shall mean the period commencing as of the Effective Date and continuing
in effect through April 1, 2008; PROVIDED, HOWEVER, that commencing on April 1,
2008 and each April 1st thereafter, the Term shall be automatically extended for
one additional year unless, not later than 90 days prior to the

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scheduled expiration of the Term (or any extension thereof), the Company shall
have given the Executive written notice that the Term will not be extended.

        3. EMPLOYMENT STATUS; TERMINATION FOLLOWING CHANGE IN CONTROL.

                3.1.    NOT AN EMPLOYMENT CONTRACT. The Executive acknowledges
        that this Agreement does not constitute a contract of employment or
        impose on the Company any obligation to retain the Executive as an
        employee and that this Agreement does not prevent the Executive from
        terminating employment at any time. If the Executive's employment with
        the Company terminates for any reason and subsequently a Change in
        Control shall occur, the Executive shall not be entitled to any benefits
        hereunder except as otherwise provided pursuant to Section 1.2.

                3.2.    TERMINATION OF EMPLOYMENT.

                        (a) If the Change in Control Date occurs during the
                Term, any termination of the Executive's employment by the
                Company or by the Executive within 12 months following the
                Change in Control Date (other than due to the death of the
                Executive) shall be communicated by a written notice to the
                other party hereto (the "Notice of Termination"), given in
                accordance with Section 7. Any Notice of Termination shall:

                             (i)   indicate the specific termination provision
                                   (if any) of this Agreement relied upon by the
                                   party giving such notice,

                             (ii)  to the extent applicable, set forth in
                                   reasonable detail the facts and circumstances
                                   claimed to provide a basis for termination of
                                   the Executive's employment under the
                                   provision so indicated and

                             (iii) specify the Date of Termination (as defined
                                   below).

                The effective date of an employment termination (the "Date of
                Termination") shall be the close of business on the date
                specified in the Notice of Termination (which date may not be
                less than 15 days or more than 120 days after the date of
                delivery of such Notice of Termination), in the case of a
                termination other than one due to the Executive's death, or the
                date of the Executive's death, as the case may be. In the event
                the Company fails to satisfy the requirements of Section 3.2(a)
                regarding a Notice of Termination, the purported termination of
                the Executive's employment pursuant to such Notice of
                Termination shall not be effective for purposes of this
                Agreement.

                        (b)  The failure by the Executive or the Company to set
                forth in the Notice of Termination any fact or circumstance that
                contributes to a showing of Good Reason or Cause shall not waive
                any right of the Executive or the Company, respectively,
                hereunder or preclude the Executive or the Company,
                respectively, from asserting any such fact or circumstance in
                enforcing the Executive's or the Company's rights hereunder.

                        (c)  Any Notice of Termination for Cause given by the
                Company must be given within 90 days of the occurrence of the
                event(s) or circumstance(s) that constitute(s) Cause. Prior to
                any Notice of Termination for Cause being given (and prior to
                any termination for Cause being effective), the Executive shall
                be entitled to a hearing before the Board of Directors of the
                Company at which the Executive may, at the Executive's election,
                be represented by counsel and at which the Executive shall have
                a reasonable opportunity to be heard. Such hearing shall be held
                on not less than 15 days prior written notice to the Executive
                stating the Board of Directors' intention to terminate the
                Executive for Cause and stating in detail the particular

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                event(s) or circumstance(s) that the Board of Directors believes
                constitutes Cause for termination.

                        (d)  Any Notice of Termination for Good Reason given by
                the Executive must be given within 60 days of the occurrence of
                the event(s) or circumstance(s) that constitute(s) Good Reason.

        4. BENEFITS TO EXECUTIVE.

                4.1.    COMPENSATION AND STOCK ACCELERATION. If the Change in
        Control Date occurs during the Term and the Executive's employment with
        the Company terminates within 12 months following the Change in Control
        Date, the Executive shall be entitled to the following benefits:

                        (a)  If the Executive's employment with the Company is
                terminated by the Company (other than for Cause, Disability or
                death) or by the Executive for Good Reason within 12 months
                following the Change in Control Date, then the Executive shall
                be entitled to the following benefits:

                             (i)   the Company shall pay to the Executive in a
                                   lump sum in cash within 30 days after the
                                   Date of Termination the aggregate of the
                                   following amounts:

                                   (1)  the sum of (A) the Executive's base
                                        salary through the Date of Termination,
                                        (B) the product of (x) the annual bonus
                                        paid or payable (including any bonus or
                                        portion thereof that has been earned but
                                        deferred) for the most recently
                                        completed fiscal year and (y) a
                                        fraction, the numerator of which is the
                                        number of days in the current fiscal
                                        year through the Date of Termination,
                                        and the denominator of which is 365 and
                                        (C) any accrued vacation pay, in each
                                        case to the extent not previously paid;
                                        and

                                   (2)  the amount equal to the sum of (x) the
                                        Executive's highest annual base salary
                                        during the five-year period prior to the
                                        Change in Control Date and (y) the
                                        Executive's highest annual bonus during
                                        the five-year period prior to the Change
                                        in Control Date.

                             (ii)  for 12 months after the Date of Termination,
                                   or such longer period as may be provided by
                                   the terms of the appropriate plan, program,
                                   practice or policy, the Company shall
                                   continue to provide benefits to the Executive
                                   and the Executive's family at least equal to
                                   those that would have been provided to them
                                   if the Executive's employment had not been
                                   terminated, in accordance with the applicable
                                   Benefit Plans in effect on the Measurement
                                   Date or, if more favorable to the Executive
                                   and the Executive's family, in effect
                                   generally at any time thereafter with respect
                                   to other peer executives of the Company and
                                   its affiliated companies; PROVIDED, HOWEVER,
                                   that if the Executive becomes reemployed with
                                   another employer and is eligible to receive a
                                   particular type of benefits (e.g., health
                                   insurance benefits) from such employer on
                                   terms at least as favorable to the Executive
                                   and the Executive's family as those being
                                   provided by the Company, then the Company
                                   shall no longer be required to provide those
                                   particular benefits to the Executive and the
                                   Executive's family;

                             (iii) to the extent not previously paid or
                                   provided, the Company shall timely pay or
                                   provide to the Executive any other amounts or
                                   benefits required to be paid or

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                                   provided or that the Executive is eligible to
                                   receive following the Executive's termination
                                   of employment under any plan, program,
                                   policy, practice, contract or agreement of
                                   the Company and its affiliated companies; and

                             (iv)  for purposes of determining eligibility (but
                                   not the time of commencement of benefits) of
                                   the Executive for retiree benefits to which
                                   the Executive is entitled, the Executive
                                   shall be considered to have remained employed
                                   by the Company until 12 months after the Date
                                   of Termination.

                             (v)   if the Change in Control relating to such
                                   Change in Control Date did not constitute a
                                   Qualifying Option Event under any Qualifying
                                   Option held by the Executive, then:

                                   (1)  any such Qualifying Option that provides
                                        for acceleration of vesting in full upon
                                        a Qualifying Option Event shall become
                                        immediately exercisable in full as of
                                        the Date of Termination; and

                                   (2)  the vesting of any other such Qualifying
                                        Option shall accelerate in part, with
                                        the number of shares so vesting being
                                        equal to the number of shares that would
                                        have vested as of the date of the
                                        Qualifying Option Event, assuming such
                                        Change in Control would have constituted
                                        a Qualifying Option Event.

                        (b)  If the Executive voluntarily terminates the
                Executive's employment with the Company within 12 months
                following the Change in Control Date, excluding a termination
                for Good Reason, or if the Executive's employment with the
                Company is terminated by reason of the Executive's death or
                Disability within 12 months following the Change in Control
                Date, then the Company shall (i) pay the Executive (or the
                Executive's estate, if applicable), in a lump sum in cash within
                30 days after the Date of Termination, the amounts due pursuant
                to clauses (A), (B) and (C) of Section 4.1(a)(i)(1) and (ii)
                timely pay or provide to the Executive the amounts due pursuant
                to Section 4.1(iii).

                        (c)  If the Company terminates the Executive's
                employment with the Company for Cause within 12 months following
                the Change in Control Date, then the Company shall (i) pay the
                Executive, in a lump sum in cash within 30 days after the Date
                of Termination, the sum of the Executive's annual base salary
                through the Date of Termination, to the extent not previously
                paid, and (ii) timely pay or provide to the Executive the
                amounts due pursuant to Section 4.1(iii)

                4.2.    TAXES.

                        (a)  In the event that the Company undergoes a "Change
                in Ownership or Control" (as defined below), the Company shall,
                within 30 days after each date on which the Executive becomes
                entitled to receive (whether or not then due) a Contingent
                Compensation Payment (as defined below) relating to such Change
                in Ownership or Control, determine and notify the Executive
                (with reasonable detail regarding the basis for its
                determinations) (i) which of the payments or benefits due to the
                Executive (under this Agreement or otherwise) following such
                Change in Ownership or Control constitute Contingent
                Compensation Payments, (ii) the amount, if any, of the excise
                tax (the "Excise Tax") payable pursuant to Section 4999 of the
                Internal Revenue Code of 1986, as amended (the "Code"), by the
                Executive with respect to such Contingent Compensation Payment
                and (iii) the amount of the Gross-Up Payment (as defined below)
                due to the Executive with respect to such Contingent
                Compensation Payment.

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                Within 30 days after delivery of such notice to the Executive,
                the Executive shall deliver a response to the Company (the
                "Executive Response") stating either (A) that the Executive
                agrees with the Company's determination pursuant to the
                preceding sentence or (B) that the Executive disagrees with such
                determination, in which case the Executive shall indicate which
                payment and/or benefits should be characterized as a Contingent
                Compensation Payment, the amount of the Excise Tax with respect
                to such Contingent Compensation Payment and the amount of the
                Gross-Up Payment due to the Executive with respect to such
                Contingent Compensation Payment. The amount and characterization
                of any item in the Executive Response shall be final; provided,
                however, that in the event that the Executive fails to deliver
                an Executive Response on or before the required date, the
                Company's initial determination shall be final. Within 90 days
                after the due date of each Contingent Compensation Payment to
                the Executive, the Company shall pay to the Executive, in cash,
                the Gross-Up Payment with respect to such Contingent
                Compensation Payment, in the amount determined pursuant to this
                Section 4.2(a).

                        (b)  For purposes of this Section 4.2, the following
                terms shall have the following respective meanings:

                             (i)   "Change in Ownership or Control" shall mean a
                                   change in the ownership or effective control
                                   of the Company or in the ownership of a
                                   substantial portion of the assets of the
                                   Company determined in accordance with Section
                                   280G(b)(2) of the Code.

                             (ii)  "Contingent Compensation Payment" shall mean
                                   any payment (or benefit) in the nature of
                                   compensation that is made or made available
                                   (under this Agreement, the terms of any stock
                                   option agreement (whether outstanding as of
                                   the date of this agreement or granted
                                   subsequently, even if the vesting of options
                                   granted thereunder may be accelerated by an
                                   event or occurrence that constitutes a Change
                                   in Control for purposes of this agreement),
                                   or otherwise) to a "disqualified individual"
                                   (as defined in Section 280G(c) of the Code)
                                   and that is contingent (within the meaning of
                                   Section 280G(b)(2)(A)(i) of the Code) on a
                                   Change in Ownership or Control of the
                                   Company.

                             (iii) "Gross-Up Payment" shall mean an amount equal
                                   to the sum of (i) the amount of the Excise
                                   Tax payable with respect to a Contingent
                                   Compensation Payment and (ii) the amount
                                   necessary to pay all additional taxes imposed
                                   on (or economically borne by) the Executive
                                   (including the Excise Taxes, state and
                                   federal income taxes and all applicable
                                   employment taxes) attributable to the receipt
                                   of such Gross-Up Payment. For purposes of the
                                   preceding sentence, all taxes attributable to
                                   the receipt of the Gross-Up Payment shall be
                                   computed assuming the application of the
                                   maximum tax rates provided by law.

                4.3.    MITIGATION. The Executive shall not be required to
        mitigate the amount of any payment or benefits provided for in this
        Section 4 by seeking other employment or otherwise. Further, except as
        provided in Section 4.1(a)(ii), the amount of any payment or benefits
        provided for in this Section 4 shall not be reduced by any compensation
        earned by the Executive as a result of employment by another employer,
        by retirement benefits, by offset against any amount claimed to be owed
        by the Executive to the Company or otherwise.

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        5. DISPUTES.

                5.1.    SETTLEMENT OF DISPUTES; ARBITRATION. All claims by the
        Executive for benefits under this Agreement shall be directed to and
        determined by the Board of Directors of the Company and shall be in
        writing. Any denial by the Board of Directors of a claim for benefits
        under this Agreement shall be delivered to the Executive in writing and
        shall set forth the specific reasons for the denial and the specific
        provisions of this Agreement relied upon. The Board of Directors shall
        afford a reasonable opportunity to the Executive for a review of the
        decision denying a claim. Any further dispute or controversy arising
        under or in connection with this Agreement shall be settled exclusively
        by arbitration in Boston, Massachusetts, in accordance with the rules of
        the American Arbitration Association then in effect. Judgment may be
        entered on the arbitrator's award in any court having jurisdiction.

                5.2.    EXPENSES. The Company agrees to pay as incurred, to the
        full extent permitted by law, all legal, accounting and other fees and
        expenses that the Executive may reasonably incur as a result of any
        claim or contest (regardless of the outcome thereof) by the Company, the
        Executive or others regarding the validity or enforceability of, or
        liability under, any provision of this Agreement or any guarantee of
        performance thereof (including as a result of any contest by the
        Executive regarding the amount of any payment or benefits pursuant to
        this Agreement), plus in each case interest on any delayed payment at
        the applicable Federal rate provided for in Section 7872(f)(2)(A) of the
        Code.

        6. SUCCESSORS.

                6.1.    SUCCESSOR TO COMPANY. The Company shall require any
        successor (whether direct or indirect, by purchase, merger,
        consolidation or otherwise) to all or substantially all of the business
        or assets of the Company expressly to assume and agree to perform this
        Agreement to the same extent that the Company would be required to
        perform it if no such succession had taken place. Failure of the Company
        to obtain an assumption of this Agreement at or prior to the
        effectiveness of any succession shall be a breach of this Agreement and
        shall constitute Good Reason if the Executive elects to terminate
        employment, except that for purposes of implementing the foregoing, the
        date on which any such succession becomes effective shall be deemed the
        Date of Termination. As used in this Agreement, "Company" shall mean the
        Company as defined above and any successor to its business or assets as
        aforesaid that assumes and agrees to perform this Agreement, by
        operation of law or otherwise.

                6.2.    SUCCESSOR TO EXECUTIVE. This Agreement shall inure to
        the benefit of and be enforceable by the Executive's personal or legal
        representatives, executors, administrators, successors, heirs,
        distributees, devisees and legatees. If the Executive should die while
        any amount would still be payable to the Executive or the Executive's
        family hereunder if the Executive had continued to live, all such
        amounts, unless otherwise provided herein, shall be paid in accordance
        with the terms of this Agreement to the executors, personal
        representatives or administrators of the Executive's estate.

        7. NOTICE.

        All notices, instructions and other communications given hereunder or in
connection herewith shall be in writing. Any such notice, instruction or
communication shall be sent either:

        (a)     by registered or certified mail, return receipt requested,
                postage prepaid, or

        (b)     prepaid via a reputable nationwide overnight courier service,

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in each case addressed to the Company, at 250 First Avenue, Needham,
Massachusetts 02494, Attention: President, and to the Executive at the
Executive's address indicated on the signature page of this Agreement (or to
such other address as either the Company or the Executive may have furnished to
the other in writing in accordance herewith). Any such notice, instruction or
communication shall be deemed to have been delivered five business days after it
is sent by registered or certified mail, return receipt requested, postage
prepaid, or one business day after it is sent via a reputable nationwide
overnight courier service. Either party may give any notice, instruction or
other communication hereunder using any other means, but no such notice,
instruction or other communication shall be deemed to have been duly delivered
unless and until it actually is received by the party for whom it is intended.

        8. MISCELLANEOUS.

                8.1.    EMPLOYMENT BY SUBSIDIARY. For purposes of this
        Agreement, the Executive's employment with the Company shall not be
        deemed to have terminated solely as a result of the Executive continuing
        to be employed by a wholly owned subsidiary of the Company.

                8.2.    SEVERABILITY. The invalidity or unenforceability of any
        provision of this Agreement shall not affect the validity or
        enforceability of any other provision of this Agreement, which shall
        remain in full force and effect.

                8.3.    INJUNCTIVE RELIEF. The Company and the Executive agree
        that any breach of this Agreement by the Company is likely to cause the
        Executive substantial and irrevocable damage and therefore, in the event
        of any such breach, in addition to such other remedies that may be
        available, the Executive shall have the right to specific performance
        and injunctive relief.

                8.4.    GOVERNING LAW. The validity, interpretation,
        construction and performance of this Agreement shall be governed by the
        internal laws of the Commonwealth of Massachusetts, without regard to
        conflicts of law principles.

                8.5.    WAIVERS. No waiver by the Executive at any time of any
        breach of, or compliance with, any provision of this Agreement to be
        performed by the Company shall be deemed a waiver of that or any other
        provision at any subsequent time.

                8.6.    COUNTERPARTS. This Agreement may be executed in
        counterparts, each of which shall be deemed to be an original but both
        of which together shall constitute one and the same instrument.

                8.7.    TAX WITHHOLDING. Any payments provided for hereunder
        shall be paid net of any applicable tax withholding required under
        federal, state or local law.

                8.8.    ENTIRE AGREEMENT. This Agreement sets forth the entire
        agreement of the parties hereto in respect of the subject matter
        contained herein and supersedes all prior agreements, promises,
        covenants, arrangements, communications, representations or warranties,
        whether oral or written, by any officer, employee or representative of
        any party hereto in respect of the subject matter contained herein; and
        any prior agreement of the parties hereto in respect of the subject
        matter contained herein is hereby terminated and cancelled.
        Notwithstanding the foregoing, this Agreement shall not be deemed to
        supersede, in part or in whole, the terms of any stock option agreement,
        whether outstanding as of the date of this Agreement or granted
        subsequently, even if the vesting of options granted thereunder may be
        accelerated by an event or occurrence that constitutes a Change in
        Control for purposes of this Agreement.

                8.9.    CONSTRUCTION. The headings of the Sections of this
        Agreement are included only for convenience and shall not affect the
        meaning or interpretation of this Agreement. References herein

                                      -11-
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        to Sections shall mean such Sections of this Agreement, except as
        otherwise specified. The words "herein" and "hereof" and other words of
        similar import refer to this Agreement as a whole and not to any
        particular part of this Agreement. The word "including" as used herein
        shall not be construed so as to exclude any other thing not referred to
        or described.

                8.10.   AMENDMENTS. This Agreement may be amended or modified
        only by a written instrument executed by both the Company and the
        Executive.

                8.11.   EXECUTIVE'S ACKNOWLEDGEMENTS. The Executive acknowledges
        that the Executive:

                        (a)  has read this Agreement;

                        (b)  has been represented in the preparation,
                             negotiation, and execution of this Agreement by
                             legal counsel of the Executive's own choice or has
                             voluntarily declined to seek such counsel;

                        (c)  understands the terms and consequences of this
                             Agreement; and

                        (d)  understands that the law firm of Wilmer Cutler
                             Pickering Hale and Dorr LLP is acting as counsel to
                             the Company in connection with the transactions
                             contemplated by this Agreement, and is not acting
                             as counsel for the Executive.

        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first set forth above.

                                   BROOKTROUT, INC.


                                   By: /s/ Eric R. Giler
                                       -------------------------------------
                                       President and Chief Executive Officer


                                   /s/ R. Andrew O'Brien
                                   -----------------------------------------
                                   R. ANDREW O'BRIEN

                                   Address:

                                   6 Ashmont Road
                                   -----------------------------------------

                                   Waban, MA 02468
                                   -----------------------------------------

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


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