<PAGE>   1

Coherent Communications Systems Corporation                      EXHIBIT 10.4




                   COHERENT COMMUNICATIONS SYSTEMS CORPORATION
               AMENDED AND RESTATED 1993 EQUITY COMPENSATION PLAN

SECTION 1.        Purpose; Definitions

     The purpose of the Coherent Communications Systems Corporation 1993 Equity
Compensation Plan (the "Plan") is to provide employees (including employees who
are also officers or directors), non-employee directors, and Eligible
Independent Contractors (as hereinafter defined) of Coherent Communications
Systems Corporation (the "Company") with the opportunity to receive grants of
incentive stock options, nonqualified stock options, stock appreciation rights
and restricted stock awards. The Company believes that the Plan will enable the
Company to attract, retain and motivate its employees, non-employee directors
and Eligible Independent Contractors, will encourage Plan participants to
contribute materially to the growth of the Company for the benefit of the
Company's stockholders, and will align the economic interests of the Plan
participants with those of the stockholders.

     For the purposes of the Plan, the following terms shall be defined as set
forth below:

          a. "Board" means the Board of Directors of the Company.

          b. "Code" means the Internal Revenue Code of 1986, as amended from
     time to time, and any successor thereto.

          c. "Committee" means the Committee designated by the Board to
     administer the Plan.

          d. "Company" means Coherent Communications Systems Corporation, its
     subsidiaries or any successor organization.

          e. "Disability" means permanent and total disability within the
     meaning of Section-22(e)(3) of the Code.

          f. "Eligible Independent Contractor" means an independent consultant
     or advisor hired by the Company to provide bona fide services for the
     Company that are not in connection with the offer or sale of securities in
     a capital-raising transaction.

          g. "Employed by the Company" shall mean employment as an employee or
     Eligible Independent Contractor or member of the Board, so that for
     purposes of exercising Stock Options and Stock Appreciation Rights and
     satisfying conditions with respect to Restricted Stock Grants, a
     Participant shall not be considered to have terminated employment until the
     Participant ceases to be an employee, Eligible Independent Contractor or
     member of the Board, unless the Committee determines otherwise.
<PAGE>   2

Coherent Communications Systems Corporation                      EXHIBIT 10.4


          h. "Exchange Act" means the Securities Exchange Act of 1934, as
     amended.

          i. "Fair Market Value" means the fair market value of the Stock as
     determined by the Committee in good faith based on the best available facts
     and circumstances at the time; provided, however, that where there is a
     public market for the Stock and the Stock is registered under the Exchange
     Act, Fair Market Value shall mean the per share or aggregate value of the
     Stock as of any given date, determined as follows: (i) if the principal
     trading market for the Stock is a national securities exchange or the
     Nasdaq National Market, the last reported sale price thereof on the
     relevant date or, if there were no trades on that date, the latest
     preceding date upon which a sale was reported, or (ii) if the Stock is not
     principally traded on such exchange or market, the mean between the last
     reported "bid" and "asked" prices of Stock on the relevant date, as
     reported on Nasdaq or, if not so reported, as reported by the National
     Daily Quotation Bureau, Inc. or as reported in a customary financial
     reporting services, as applicable and as the Committee determines.

          j. "Grant" means any Stock Option, Stock Appreciation Right or
     Restricted Stock award granted pursuant to the Plan.

          k. "Incentive Stock Option" means any Stock Option intended to be and
     designated as an "Incentive Stock Option" within the meaning of Section 422
     of the Code.

          l. "Insider" means a Participant who is subject to Section 16 of the
     Exchange Act.

          m. "Non-Qualified Stock Option" means any Stock Option that is not an
     Incentive Stock Option.

          n. "Participant" means an employee, non-employee director or Eligible
     Independent Contractor to whom an award is granted pursuant to the Plan.

          o. "Plan" means the Coherent Communications Systems Corporation 1993
     Equity Compensation Plan, as hereinafter amended from time to time.

          p. "Restricted Stock" means an award of shares of Stock that is
     subject to restrictions pursuant to Section 7 below.

          q. "Securities Act" shall mean the Securities Act of 1933, as amended.

          r. "Securities Broker" means the registered securities broker
     acceptable to the Company who agrees to effect the cashless exercise of an
     Option pursuant to Section 5(d) hereof.

          s. "Stock" means the Common Stock of the Company, par value $.01 per
     share.


                                      -2-
<PAGE>   3

Coherent Communications Systems Corporation                      EXHIBIT 10.4

          t. "Stock Appreciation Right" means the right, pursuant to an award
     granted under Section 6 below, to surrender to the Company all (or a
     portion) of a Stock Option in exchange for an amount in cash and/or shares
     of Stock equal in value to the excess of (i) the Fair Market Value, as of
     the date such right is exercised and the related Stock Option (or such
     portion thereof) is surrendered, of the shares of Stock covered by such
     Stock Option (or such portion thereof), over (ii) the aggregate exercise
     price of such Stock Appreciation Right (or such portion thereof).

          u. "Stock Option" or "Option" means any option to purchase shares of
     Stock (including Restricted Stock, if the Committee so determines) granted
     pursuant to Section 5 below.

          v. "Termination for Cause" shall mean, except to the extent specified
     otherwise by the Committee, a finding by the Committee that the Participant
     has breached his or her employment or service contract, non-competition
     agreement or other obligation with the Company, or has been engaged in
     disloyalty to the Company, including, without limitation, fraud,
     embezzlement, theft, commission of a felony or proven dishonesty in the
     course of his or her employment or service, or has disclosed trade secrets
     or confidential information of the Company to persons not entitled to
     receive such information.

SECTION 2.        Administration

     The Plan shall be administered by a Committee which shall consist of two or
more non-employee directors appointed by the Board. In the absence of the
designation of a Committee to administer the Plan, the Plan shall be
administered by the full Board.

          The Committee shall have the authority to:

          (a) select the Participants to whom Grants may from time to time be
     made hereunder;

          (b) determine the type, size and terms of the Grants to be made to
     each such Participant;

          (c) determine the time when the Grants will be made and the duration
     of any applicable exercise or restriction period, including the criteria
     for exercisability and the acceleration of exercisability;

          (d) amend the terms of any outstanding award (with the consent of the
     Participant) to reflect terms not otherwise inconsistent with the Plan,
     including, but not limited to, amendments concerning vesting acceleration
     or forfeiture waiver regarding any award or the extension of a
     Participant's right with respect to Grants under the Plan as a result of
     termination of employment or service or otherwise, based on such factors


                                      -3-
<PAGE>   4

Coherent Communications Systems Corporation                      EXHIBIT 10.4

     as the Committee shall determine, in its sole discretion, or substitution
     of new Stock Options for previously granted Stock Options, including
     previously granted Stock Options having high option prices;

          (e) establish from time to time any policy or program to encourage or
     require Participants to achieve or maintain equity ownership in the Company
     through the use of the Plan upon such terms and conditions as the Committee
     may determine in its sole discretion, and thereafter to amend, modify or
     terminate such policy or program as the Committee may from time to time
     deem appropriate; and

          (f) deal with any other matters arising under the Plan.

     The Committee shall have full power and authority to administer and
interpret the Plan and any Grant made under the Plan, to make factual
determinations and to adopt, alter and repeal such administrative rules,
guidelines, practices, agreements and instruments for implementing the Plan and
for the conduct of its business as it deems necessary or advisable, in its sole
discretion. All decisions made by the Committee pursuant to the provisions of
the Plan shall be final and binding on all persons having any interest in the
Plan or in any Grants made hereunder. All power of the Committee shall be
executed in its sole discretion, in the best interest of the Company, not as a
fiduciary, and in keeping with the objectives of the Plan.

     No member of the Board or the Committee shall be liable for any action or
determination made in good faith with respect to the Plan or any Grant made
under it. Nothing herein shall be deemed to expand the personal liability of a
member of the Board or Committee beyond that which may arise under any
applicable standards set forth in the Company's Certificate of Incorporation,
by-laws and Delaware law, nor shall anything herein limit any rights to
indemnification or advancement of expenses to which any member of the Board or
the Committee may be entitled under any applicable law, the Company's
Certificate of Incorporation or by-laws, agreement, vote of the stockholders or
directors, or otherwise.

SECTION 3.        Stock Subject to the Plan

     (a) The aggregate number of shares of Stock that may be issued or
transferred under the Plan is 1,500,000, subject to adjustment pursuant to
Section 3(b) below. Such shares may be authorized but unissued shares or
reacquired shares of Stock, including shares purchased by the Company on the
open market for purposes of the Plan. In the event the number of shares of Stock
issued under the Plan and the number of shares of Stock subject to outstanding
awards equals the maximum number of shares of Stock authorized under the Plan,
no further awards shall be made unless the Plan is amended to increase the
number of shares of Stock issuable and transferable hereunder or additional
shares of Stock become available for further awards under the Plan. If and to
the extent that Options or Stock Appreciation Rights granted under the


                                      -4-
<PAGE>   5

Coherent Communications Systems Corporation                      EXHIBIT 10.4

Plan terminate, expire or are canceled, forfeited, exchanged or surrendered
without having been exercised, or if any shares of Restricted Stock are
forfeited, the shares subject to such Grants shall again be available for
subsequent awards under the Plan.

     (b) If there is any change in the number or kind of shares of Company Stock
outstanding (i) by reason of a stock dividend, spin off, recapitalization, stock
split, or combination or exchange of shares, (ii) by reason of a merger,
reorganization or consolidation in which the Company is the surviving
corporation, (iii) by reason of a reclassification or change in par value, or
(iv) by reason of any other extraordinary or unusual event affecting the
outstanding Company Stock as a class without the Company's receipt of
consideration, or if the value of outstanding shares of Company Stock is
substantially reduced as a result of a spin off or the Company's payment of an
extraordinary dividend or distribution, then unless such event or change results
in the termination of all outstanding awards under the Plan, the Committee shall
preserve the value of the outstanding awards by adjusting the maximum number and
class of shares issuable under the Plan to reflect the effect of such event or
change in the Company's capital structure, and by making appropriate adjustments
to the number and class of shares subject to an outstanding award and/or the
option price of each outstanding Option and Stock Appreciation Right, except
that any fractional shares resulting from such adjustments shall be eliminated
by rounding any portion of a share equal to .5 or greater up, and any portion of
a share equal to less than .5 down, in each case to the nearest whole number.

SECTION 4.        Eligibility; Participant Limitations Concerning Issuances

     All employees, non-employee directors and Eligible Independent Contractors
are eligible to participate in the Plan. The maximum aggregate number of shares
of Stock that shall be subject to Grants made under the Plan to any Participant
shall not exceed 600,000. The terms and provisions of Grants made under the Plan
may vary between Participants or as to the same Participant to whom more than
one Grant may be awarded.

SECTION 5.        Stock Options

     Stock Options may be granted alone, in addition to, or in tandem with other
awards granted under the Plan. Any Stock Option granted under the Plan shall be
in such form as the Committee may from time to time approve. Stock Options
granted under the Plan may be of two types: (i) Incentive Stock Options and (ii)
Non-Qualified Stock Options.

     The Committee shall have the authority to grant Incentive Stock Options,
Non-Qualified Stock Options or both types of Stock Options (in each case with or
without Stock Appreciation Rights). To the extent that any Stock Option does not
qualify as an Incentive Stock Option, it shall constitute a Non-Qualified Stock
Option.


                                      -5-
<PAGE>   6

Coherent Communications Systems Corporation                      EXHIBIT 10.4

     Anything in the Plan to the contrary notwithstanding, no term of this Plan
relating to Incentive Stock Options shall be interpreted, amended or altered,
nor shall any discretion or authority granted under the Plan be so exercised, so
as to disqualify the Plan under Section 422 of the Code, or, without the consent
of the Participant affected, to disqualify any Incentive Stock Option under
Section 422.

     Options granted under the Plan shall be subject to the following terms and
conditions and shall contain such additional terms and conditions, not
inconsistent with the terms of the Plan, as the Committee shall deem
appropriate:

     (a) Option Price. The option price per share of Stock purchasable under a
Stock Option shall be determined by the Committee at the time of grant,
provided, however, that the option price per share for any Incentive Stock
Option shall be not less than 100% of the Fair Market Value of the Stock at the
time of grant.

     Any Incentive Stock Option granted to any Participant who, at the time the
Option is granted, owns more than 10% of the voting power of all classes of
stock of the Company or of a Parent or Subsidiary corporation (within the
meaning of Section 424 of the Code), shall have an exercise price no less than
110% of the Fair Market Value per share on the date of the grant.

     (b) Option Term. The term of each Stock Option shall be fixed by the
Committee, but no Stock Option shall be exercisable more than ten years after
the date the Stock Option is granted. However, any Incentive Stock Option
granted to any Participant who, at the time the Option is granted, owns more
than 10% of the voting power of all classes of stock of the Company or of a
Parent or Subsidiary corporation may not have a term of more than five years. No
Stock Option may be exercised by any person after expiration of the term of the
Stock Option.

     (c) Exercisability. Stock Options shall be exercisable at such time or
times and subject to such terms and conditions as shall be determined by the
Committee at or after grant. If the Committee provides, in its discretion, that
any Stock Option is exercisable only in installments, the Committee may waive
such installment exercise provisions at any time at or after grant in whole or
in part, based on such factors as the Committee shall determine, in its sole
discretion.

     (d) Method of Exercise. Subject to whatever installment exercise provisions
apply under Section 5(c), Stock Options may be exercised, in whole or in part at
any time and from time to time during the Option period, by giving written
notice of exercise to the Company specifying the number of shares to be
purchased. Such notice shall be accompanied by payment in full of the purchase
price, either by cash, check, or such other instrument as the Committee may
accept. As determined by the Committee, in its sole discretion, at or after
grant,


                                      -6-
<PAGE>   7

Coherent Communications Systems Corporation                      EXHIBIT 10.4

payment in full or in part may also be made in the form of unrestricted Stock
already owned by the Participant (including Company Stock acquired in connection
with the exercise of an Option, subject to such restrictions as the Committee
deems appropriate); provided, however, that (i) in the case of an Incentive
Stock Option, the right to make a payment in the form of unrestricted Stock
already owned by the Participant may be authorized only at the time the Option
is granted and (ii) the Company may require that the Stock has been owned by the
Participant for the requisite period of time necessary to avoid a charge to the
Company's earnings for financial reporting purposes and adverse accounting
consequences to the Company with respect to the Option.

     If specified by the Committee in the agreement governing a Stock Option at
the time of grant, the Committee may, in its sole discretion, upon receipt of
such Participant's written notice to exercise, elect to cash out all or part of
the portion of the Stock Option to be exercised by paying the Participant an
amount, in cash or Stock, equal to the excess of the Fair Market Value of the
Stock over the option price on the effective date of such cash-out.

     To the extent permitted under the applicable laws and regulations, at the
request of the Participant and if authorized by the Committee, in its sole
discretion, at or after grant, the Company agrees to cooperate in a "cashless
exercise" of a Stock Option. The cashless exercise shall be effected by the
Participant delivering to the Securities Broker instructions to sell a
sufficient number of shares of Stock to cover the cost and expenses associated
therewith.

     No shares of Stock shall be issued until full payment therefor has been
made. A Participant shall not have any right to dividends or other rights of a
stockholder with respect to shares subject to the Option until such time as
Stock is issued in the name of the Participant following exercise of the Option
in accordance with the Plan.

     (e) Stock Option Agreement. Each Option granted under this Plan shall be
evidenced by an appropriate Stock Option agreement, which agreement shall
expressly specify whether such Option is an Incentive Stock Option or a
Non-Qualified Stock Option and shall be executed by the Company and the
Participant. The agreement shall contain such terms and provisions, not
inconsistent with the Plan, as shall be determined by the Committee.

     (f) Replacement Options. The Committee may, in its sole discretion and at
the time of the original option grant, authorize the Participant to
automatically receive replacement Options pursuant to this part of the Plan. Any
such replacement option shall be granted upon such terms and subject to such
conditions and limitations as the Committee may deem appropriate. Any
replacement option shall cover a number of shares determined by the Committee,
but in no event equal to more than the number of shares covered by the original
option exercised. The per share exercise price of any replacement option shall
equal the then current Fair Market Value of a share of Stock, and


                                      -7-
<PAGE>   8

Coherent Communications Systems Corporation                      EXHIBIT 10.4

shall have a term as determined by the Committee at the time of grant of the
original Option.

     The Committee shall have the right, and may reserve the right in any Option
grant, in its sole discretion and at any time, to discontinue the automatic
grant of replacement options if it determines the continuance of such grants to
no longer be in the best interest of the Company.

     (g) Non-transferability of Options. Except as provided below, no Stock
Option shall be transferable by the Participant other than by will or by the
laws of descent and distribution, and all Stock Options shall be exercisable,
during the Participant's lifetime, only by the Participant. When a Participant
dies, the representative or other person entitled to succeed to the rights of
the Grantee may exercise such rights, subject to the Company receiving
satisfactory proof of his or her right to receive the Grant under the
Participant's will or under the applicable laws of descent and distribution.
Notwithstanding the foregoing, the Committee may provide, at or after Grant,
that a Participant may transfer Nonqualified Stock Options pursuant to a
domestic relations order or to family members or other persons or entities
according to such terms as the Committee may determine.

     (h) Termination of Employment; Disability; Death

          (i) Unless otherwise determined by the Committee at or after grant, in
     the event of a Participant's termination of employment (voluntary or
     involuntary) for any reason other than as provided below, any Stock Option
     held by such Participant may thereafter be exercised by the Participant, to
     the extent it was exercisable at the time of such termination or on such
     accelerated basis as the Committee may determine at or after grant, for a
     period of three months (or such shorter period as the Committee may specify
     at grant) from the date of such termination of employment or until the
     expiration of the stated term of such Stock Option, whichever period is
     shorter.

          (ii) Unless otherwise determined by the Committee at or after grant,
     if any Participant ceases to be employed by the Company on account of a
     Termination for Cause by the Company, any Stock Option held by such
     Participant shall terminate as of the date the Participant ceases to be
     employed by the Company, and the Participant shall automatically forfeit
     all Stock underlying any exercised portion of an Option for which the
     Company has not yet delivered the share certificates, upon refund by the
     Company of the Exercise Price paid by the Participant for such Stock.

          (iii) Unless otherwise determined by the Committee at or after grant,
     if a Participant's employment by the Company terminates by reason of
     Disability, any Stock Option held by such Participant may thereafter be
     exercised by the Participant, to the extent it was exercisable at the time


                                      -8-
<PAGE>   9

Coherent Communications Systems Corporation                      EXHIBIT 10.4

     of termination, or on such accelerated basis as the Committee may determine
     at or after grant, for a period of one year (or such shorter period as the
     Committee may specify at grant) from the date of such termination of
     employment or until the expiration of the stated term of such Stock Option,
     whichever period is shorter.

          (iv) Unless otherwise determined by the Committee at or after grant,
     if any Participant dies while employed by the Company or within three
     months after the date on which the Participant ceases to be employed by the
     Company on account of termination of employment specified in Section
     5(h)(i) above (or within such other period of time as may be specified by
     the Committee), any Stock Option held by such Participant may thereafter be
     exercised, to the extent then exercisable or on such accelerated basis as
     the Committee may determine at or after grant, by the legal representative
     of the estate or by the legatee of the Participant under the will of the
     Participant, for a period of one year (or such shorter period as the
     Committee may specify at grant) from the date of such termination of
     employment or until the expiration of the stated term of such Stock Option,
     whichever period is shorter.

          (i) Incentive Stock Option Limitation. The aggregate Fair Market Value
     (determined as of the time of grant) of the Stock with respect to which
     Incentive Stock Options are exercisable for the first time by the
     Participant during any calendar year under the Plan and/or any other stock
     option plan of the Company shall not exceed $100,000. An Incentive Stock
     Option shall not be granted to any person who is not an employee of the
     Company or a parent or subsidiary (within the meaning of section 424(f) of
     the Code).

          (j) Issuance of Shares Issuance of Shares and Compliance with
     Securities Acts. Within a reasonable time after exercise of an Option, the
     Company shall cause to be delivered to the Participant a certificate for
     the Stock purchased pursuant to the exercise of the Option.


                                      -9-
<PAGE>   10

Coherent Communications Systems Corporation                      EXHIBIT 10.4

SECTION 6.         Stock Appreciation Rights

     (a) Grant and Exercise. Stock Appreciation Rights may be granted either
separately or in tandem with all or part of any Stock Option granted under the
Plan. The provisions of Stock Appreciation Rights awarded under the Plan need
not be the same with respect to each Participant. In the case of a Non-Qualified
Stock Option, such rights may be granted either at the grant of such Stock
Option or at any time thereafter while the Option remains outstanding. In the
case of an Incentive Stock Option, such rights may be granted only at the time
of the grant of such Stock Option. The Committee shall establish the base amount
of the Stock Appreciation Rights at the time the Stock Appreciation Right is
granted. Unless the Committee determines otherwise, the base amount of each
Stock Appreciation Right shall be equal to the per share option price of the
related Stock Option or, if there is no related Stock Option, the Fair Market
Value of a share of Stock as of the date of grant of such Stock Appreciation
Right.

     A Stock Appreciation Right or applicable portion thereof granted with
respect to a given Stock Option shall terminate and no longer be exercisable
upon the termination or exercise of the related Stock Option, except that,
unless otherwise determined by the Committee, in its sole discretion, at the
time of grant, a Stock Appreciation Right granted with respect to less than the
full number of shares covered by a related Stock Option shall not be reduced
until the number of shares covered by an exercise or termination of the related
Stock Option exceeds the number of shares not covered by the Stock Appreciation
Right.

     A Stock Appreciation Right may be exercised by a Participant, in accordance
with Section 6(b), by surrendering the applicable portion of the related Stock
Option. Upon such exercise and surrender, the Participant shall be entitled to
receive an amount determined in the manner prescribed in Section 6(b). Stock
Options which have been so surrendered, in whole or in part, shall no longer be
exercisable to the extent the related Stock Appreciation Rights have been
exercised.

     (b) Terms and Conditions. Stock Appreciation Rights shall be subject to
such terms and conditions, not inconsistent with the provisions of the Plan, as
shall be determined from time to time by the Committee, including the following:

          (i) Stock Appreciation Rights shall be exercisable only at such time
     or times and to the extent that the Stock Options to which they relate, if
     any, shall be exercisable in accordance with the provisions of Section 5
     and this Section 6 of the Plan.

          (ii) Upon the exercise of a Stock Appreciation Right, a Participant
     shall be entitled to receive up to, but not more than, an amount in cash


                                      -10-
<PAGE>   11

Coherent Communications Systems Corporation                      EXHIBIT 10.4

     and/or shares of Stock equal in value to the excess of the Fair Market
     Value of one share of Stock (as of the date the Stock Appreciation Right is
     exercised and the related Stock Option is surrendered) over the exercise
     price of the Stock Appreciation Right, multiplied by the number of shares
     of Stock in respect of which the Stock Appreciation Right shall have been
     exercised, with the Committee having the right to determine the form of
     payment.

          (iii) Stock Appreciation Rights shall be transferable only when and to
     the extent that the underlying Stock Option would be transferable under
     Section 5(g) of the Plan.

          (iv) A Stock Appreciation Right granted in connection with an
     Incentive Stock Option may be exercised only if and when the market price
     of the Stock subject to the Incentive Stock Option exceeds the exercise
     price of such Stock Option.

SECTION 7.        Restricted Stock

     (a) Administration. Shares of Restricted Stock may be issued either alone
or in addition to other awards granted under the Plan. The Committee shall
determine the employees, non-employee directors or Eligible Independent
Contractors to whom, and the time or times at which, grants of Restricted Stock
will be made, the number of shares to be awarded, the price (if any) to be paid
by the recipient of Restricted Stock (subject to Section 7(b)), the time or
times within which such awards may be subject to forfeiture, and all other
conditions of the awards. The Committee may condition the grant of Restricted
Stock upon the attainment of specified performance goals or such other factors
as the Committee may determine, in its sole discretion. The provisions of
Restricted Stock awards need not be the same with respect to each Participant.

     (b) Awards and Certificates. The prospective recipient of a Restricted
Stock award shall not have any rights with respect to such award unless and
until such recipient has executed an agreement evidencing the award and has
delivered a fully executed copy thereof to the Company, and has otherwise
complied with the applicable terms and conditions of such award.

          (i) The purchase price for shares of Restricted Stock shall be
     established by the Committee and may be zero.

          (ii) Awards of Restricted Stock may be accepted within a period of 60
     days (or such shorter period as the Committee may specify at grant) after
     the grant date, by executing a Restricted Stock award agreement and paying
     whatever price (if any) is required under Section 7(b)(i).

          (iii) Each Participant receiving a Restricted Stock award shall be
     issued a certificate in respect of such shares of Restricted Stock. Such
     certificate shall be registered in the name of such Participant, and shall


                                      -11-
<PAGE>   12

Coherent Communications Systems Corporation                      EXHIBIT 10.4

     bear an appropriate legend referring to the terms, conditions, and
     restrictions applicable to such award, substantially in the following form:

          "The transferability of this certificate and the shares of stock
     represented hereby are subject to the terms and conditions (including
     forfeiture) of the Coherent Communications Systems Corporation 1993 Equity
     Compensation Plan and an Agreement entered into between the registered
     owner and Coherent Communications Systems Corporation. Copies of such Plan
     and Agreement are on file at the offices of Coherent Communications Systems
     Corporation."

          (iv) The Committee shall require that the certificates evidencing such
     Restricted Stock be held in custody by the Company until the restrictions
     thereon shall have lapsed, and that, as a condition of any Restricted Stock
     award, the Participant shall have delivered a stock power, endorsed in
     blank, relating to the Stock covered by such award.

     (c) Restrictions and Conditions. The shares of Restricted Stock awarded
pursuant to this Section 7 shall be subject to the following restrictions and
conditions:

          (i) Subject to the provisions of this Plan and the Restricted Stock
     award agreement, during a period set by the Committee commencing with the
     date of such award (the "Restriction Period"), the Participant shall not be
     permitted to sell, transfer, pledge, assign or otherwise encumber shares of
     Restricted Stock awarded under the Plan. Within these limits, the
     Committee, at its sole discretion, may provide for the lapse of such
     restrictions in installments and may accelerate or waive such restrictions
     in whole or in part, based on service, performance and/or such other
     factors or criteria as the Committee may determine, in its sole discretion.

          (ii) Except as provided in this paragraph (ii) and Section 7(c)(i),
     the Participant shall have, with respect to the shares of Restricted Stock,
     all of the rights of a stockholder of the Company, including the right to
     vote the shares and the right to receive any cash dividends. The Committee,
     in its sole discretion, as determined at the time of award, may permit or
     require the payment of cash dividends to be deferred and, if the Committee
     so determines, reinvested in additional Restricted Stock to the extent
     shares are available under Section 3.

          (iii) Subject to the applicable provisions of the Restricted Stock
     award agreement and this Section 7, upon termination of a Participant's
     employment with the Company for any reason during the Restriction Period,
     all shares still subject to restriction shall be forfeited by the
     Participant, subject to any payments for such shares as may be provided in
     the Restricted Stock award agreement.


                                      -12-
<PAGE>   13

Coherent Communications Systems Corporation                      EXHIBIT 10.4

          (iv) The Committee may, in its sole discretion, waive in whole or in
     part any or all remaining restrictions with respect to such Participant's
     shares of Restricted Stock, based on such factors as the Committee may deem
     appropriate.

          (v) If and when the Restriction Period expires without a prior
     forfeiture of the Restricted Stock subject to such Restriction Period, the
     certificates for such shares shall be delivered to the Participant
     promptly.

SECTION 8.        Withholding and Use of Shares to Satisfy Tax Obligations

     (a) Required Withholding. All Grants under the Plan shall be subject to
applicable federal (including FICA), state and local withholding requirements.
The Company shall have the right to deduct from all Grants paid in cash, or from
other wages paid to the Participant, any federal, state or local taxes required
by law to be withheld with respect to such Grants. In the case of Grants paid in
Company Stock, the Company may require the Participant or other person receiving
such Stock to pay to the Company the amount of any such taxes that the Company
is required to withhold with respect to such Grants, or the Company may deduct
from other wages paid by the Company the amount of any withholding taxes due
with respect to such Grants.

     (b) Election to Withhold Shares. If the Committee so permits, a Participant
may elect to satisfy the Company's income tax withholding obligation with
respect to a Grant paid in Company Stock by having shares withheld up to an
amount that does not exceed the Participant's maximum marginal tax rate for
federal (including FICA), state and local tax liabilities. The election must be
in a form and manner prescribed by the Committee and shall be subject to the
prior approval of the Committee.

SECTION 9.        Amendments and Termination

     The Board may amend or terminate the Plan at any time and from time to
time, but no amendment or termination shall be made which would impair the
rights of a Participant under a Grant theretofore awarded without the
Participant's consent; and provided, further, that the Board shall not amend the
Plan without stockholder approval if such approval is required pursuant to the
Code or the rules of any national securities exchange or over-the-counter market
on which the Company's Stock is then listed or included. Subject to the above
provisions, the Board shall have broad authority to amend the Plan to take into
account changes in applicable tax laws, securities laws and accounting rules, as
well as other developments.

SECTION 10.         Unfunded Status of Plan

     The Plan is intended to constitute an "unfunded" plan. The Company shall
not be required to establish any special or separate fund or to make any other


                                      -13-
<PAGE>   14

Coherent Communications Systems Corporation                      EXHIBIT 10.4

segregation of assets to assure the payment of any Grants under this Plan. In no
event shall interest be paid or accrued on any Grant, including unpaid
installments of Grants.

SECTION 11.  General Provisions

     (a) The Committee may require each person purchasing shares pursuant to a
Stock Option or receiving Stock upon the expiration of any Restriction Period
under the Plan to represent to and agree with the Company in writing that the
Participant is acquiring the shares for investment and not with a view to
distribution thereof and that such Participant will not dispose of such Stock in
any manner that would involve a violation of applicable securities laws. In such
event no Stock shall be issued to such Participant unless and until the Company
is satisfied with such representation. The certificates for such shares may
include any legend which the Committee deems appropriate to reflect any
restrictions on transfer under the Securities Act or any state securities law.

     All certificates for shares of Stock or other securities delivered under
the Plan shall be subject to such stop-transfer orders and other restrictions as
the Committee may deem advisable under the rules, regulations and other
requirements of the Securities Act, the Exchange Act, any stock exchange or
over-the-counter market upon which the Stock is then listed or included, and any
applicable federal or state securities law, and the Committee may cause a legend
or legends to be put on any such certificates to make appropriate reference to
such restrictions.

     (b) Nothing contained in this Plan shall prevent the Board from adopting
other or additional compensation arrangements, subject to stockholder approval
if such approval is required, and such arrangements may be either generally
applicable or applicable only in specific cases.

     (c) The adoption of the Plan shall not confer upon any Participant any
right to continued employment with the Company nor shall it interfere in any way
with the right of the Company to terminate its relationship with any of its
employees, directors or independent contractors at any time.

     (d) At the time of grant, the Committee may provide in connection with any
grant made under this Plan that (i) the shares of Stock received as a result of
such grant shall be subject to a right of first refusal, pursuant to which the
Participant shall be required to offer to the Company any shares that the
Participant wishes to sell, with the price being the then Fair Market Value of
the Stock, subject to such other terms and conditions as the Committee may
specify at the time of grant; and (ii) the shares of Stock received or to be
received as a result of such grant shall be subject to repurchase by the Company
upon termination of employment, subject to a repurchase price and such other
terms and conditions as the Committee may specify at the time of grant.


                                      -14-
<PAGE>   15

Coherent Communications Systems Corporation                      EXHIBIT 10.4

     (e) The reinvestment of dividends in additional Restricted Stock at the
time of any dividend payment shall only be permissible if sufficient shares of
Stock are available under Section 3 for such reinvestment.

     (d) The Committee shall establish such procedures as it deems appropriate
for a Participant to designate a beneficiary to whom any amounts payable in the
event of the Participant's death are to be paid.

     (e) The Plan shall be governed by and subject to all applicable laws and to
the approvals by any governmental or regulatory agency as may be required.

SECTION 12.  Effective Date and Term of Plan

     The Plan shall be effective as of December 10, 1993, subject to the consent
or approval of the Company's stockholders. No Stock Option, Stock Appreciation
Right or Restricted Stock award shall be granted pursuant to the Plan on or
after December 10, 2003, but awards granted prior to such tenth anniversary may
extend beyond that date; provided, however, that if the Plan is not approved by
the unanimous consent of all stockholders or by a majority of the votes cast at
a duly held meeting at which a quorum representing a majority of all outstanding
voting stock of the Company is, either in person or by proxy, present and voting
on the Plan, within 12 months after said date, the Plan and all Grants awarded
hereunder shall be null and void and no additional Grants shall be awarded
hereunder.

SECTION 13.  Interpretation

     A determination of the Committee as to any question which may arise with
respect to the interpretation of the provisions of this Plan or any Grants
awarded thereunder shall be final and conclusive, and nothing in this Plan, or
in any regulation hereunder, shall be deemed to give any Participant, his legal
representatives, assigns or any other person any right to participate herein
except to such extent, if any, as the Committee may have determined or approved
pursuant to this Plan. The Committee may consult with legal counsel who may be
counsel to the Company and shall not incur any liability for any action taken in
good faith in reliance upon the advice of such counsel.

SECTION 14.  Governing LawGoverning Law.

     With respect to any Incentive Stock Options granted pursuant to the Plan
and the agreements thereunder, the Plan, such agreements and any Incentive Stock
Options granted pursuant thereto shall be governed by the applicable Code
provisions to the maximum extent possible. Otherwise, the laws of the State of
Delaware shall govern the operation of, and the rights of Participants under,
the Plan, the agreements and any Grants awarded thereunder.

SECTION 15.  Compliance With Section 16b of the Exchange Act.


                                      -15-
<PAGE>   16

Coherent Communications Systems Corporation                      EXHIBIT 10.4

     Unless an Insider could otherwise transfer shares of Stock issued hereunder
without incurring liability under Section 16b of the Exchange Act, at least six
months must elapse from the date of grant of an Option, Stock Appreciation Right
or Restricted Stock award to the date of disposition of the Stock issued upon
exercise of such Option or Stock Appreciation Right or grant of such Restricted
Stock award.




                                      -16-