Form of Stock Purchase Agreement


                             APPLIED DIGITAL ACCESS, INC.
                   1998 EMPLOYEE STOCK PURCHASE PLAN FOR ADA CANADA
                               STOCK PURCHASE AGREEMENT


1.   I HEREBY ELECT TO PARTICIPATE IN THE APPLIED DIGITAL ACCESS, INC. 1998
     EMPLOYEE STOCK PURCHASE PLAN FOR ADA CANADA (THE "PLAN") FOR THE OPTION
     PERIOD SPECIFIED BELOW, AND I ACCORDINGLY SUBSCRIBE TO PURCHASE SHARES OF
     APPLIED DIGITAL ACCESS, INC. COMMON STOCK AT THE END OF EACH OF MY
     QUARTERLY PERIODS OF PARTICIPATION WITHIN SUCH OPTION PERIOD. 

2.   BY SEPARATE FORM, I HAVE AUTHORIZED PAYROLL DEDUCTIONS FROM EACH OF MY
     PAYCHECKS DURING MY PERIOD OF PARTICIPATION IN THE OPTION PERIOD.  SUCH
     PAYROLL DEDUCTIONS WILL BE ACCUMULATED FOR THE PURCHASE OF SHARES OF
     APPLIED DIGITAL ACCESS, INC. COMMON STOCK ON THE LAST BUSINESS DAY OF EACH
     QUARTERLY PERIOD OF PARTICIPATION.  THE PURCHASE PRICE PER SHARE WILL BE
     THE LOWER OF (i) 85% OF THE MARKET PRICE ON THE START DATE OF THE QUARTERLY
     PERIOD OF PARTICIPATION IN WHICH I FIRST ENTER THE OPTION PERIOD OR
     (ii) 85% OF THE MARKET PRICE ON EACH QUARTERLY PURCHASE DATE. HOWEVER, THE
     CLAUSE (i) AMOUNT WILL IN NO EVENT BE LESS THAN 85% OF THE MARKET PRICE ON
     THE START DATE OF THE OPTION PERIOD.

3.   THIS ENROLLMENT WILL BE EFFECTIVE FOR THE DURATION OF THE OPTION PERIOD
     SPECIFIED BELOW, AND SHARES WILL AUTOMATICALLY BE PURCHASED ON MY BEHALF AT
     THE END OF EACH QUARTERLY PERIOD OF PARTICIPATION, UNLESS I WITHDRAW FROM
     THE PLAN OR MY EMPLOYMENT TERMINATES. 

4.   MY RATE OF PAYROLL DEDUCTION WILL AUTOMATICALLY CONTINUE IN EFFECT FOR EACH
     OF MY QUARTERLY PERIODS OF PARTICIPATION WITHIN THE OPTION PERIOD, UNLESS I
     CHANGE SUCH RATE OR OTHERWISE WITHDRAW FROM THE PLAN OR MY EMPLOYMENT
     TERMINATES.

5.   I CAN WITHDRAW FROM THE PLAN AT ANY TIME AND ELECT EITHER TO HAVE THE
     COMPANY REFUND ALL MY PAYROLL DEDUCTIONS FOR THE QUARTERLY PERIOD OF
     PARTICIPATION IN WHICH I WITHDRAW OR TO HAVE SUCH PAYROLL DEDUCTIONS
     APPLIED TO THE PURCHASE OF APPLIED DIGITAL ACCESS, INC. COMMON STOCK AT THE
     END OF SUCH PERIOD.  HOWEVER, I MAY NOT REJOIN THE PLAN FOR THAT PARTICULAR
     OPTION PERIOD AT ANY LATER DATE.  UPON MY TERMINATION OF EMPLOYMENT OR
     CHANGE TO INELIGIBLE EMPLOYEE STATUS, PAYROLL DEDUCTIONS WILL AUTOMATICALLY
     CEASE ON MY BEHALF AND THE COMPANY WILL REFUND MY PAYROLL DEDUCTIONS TO
     DATE IN THE QUARTERLY PERIOD OF PARTICIPATION IN WHICH SUCH TERMINATION OR
     CHANGE OCCURS.

6.   I HAVE A COPY OF, AND AM FAMILIAR WITH, THE OFFICIAL PLAN PROSPECTUS
     SUMMARIZING THE OPERATION OF THE PLAN.  A COMPLETE COPY OF THE ACTUAL PLAN
     DOCUMENT IS ATTACHED AS EXHIBIT A TO THE PROSPECTUS.

7.   I AM TO RECEIVE A STOCK CERTIFICATE FOR THE SHARES PURCHASED ON MY BEHALF
     AFTER EACH QUARTERLY PURCHASE DATE.  THE CERTIFICATE WILL BE ISSUED AS
     INDICATED ON MY ENROLLMENT/CHANGE FORM.

8.   THE COMPANY HAS THE RIGHT TO AMEND OR TERMINATE THE PLAN AT ANY TIME, WITH
     SUCH AMENDMENT OR TERMINATION TO BECOME EFFECTIVE IMMEDIATELY FOLLOWING THE
     EXERCISE OF OUTSTANDING PURCHASE RIGHTS AT THE END OF ANY CURRENT QUARTERLY
     PERIOD OF PARTICIPATION.  SHOULD THE COMPANY ELECT TO TERMINATE THE PLAN, I
     WILL HAVE NO FURTHER RIGHTS TO PURCHASE SHARES OF APPLIED DIGITAL ACCESS,
     INC. COMMON STOCK PURSUANT TO THIS AGREEMENT.

9.   I AM FAMILIAR WITH THE PLAN RESTRICTION PROHIBITING ANY PARTICIPANT FROM
     PURCHASING MORE THAN $25,000 WORTH OF COMMON STOCK PER CALENDAR YEAR.

10.  I HAVE READ THIS AGREEMENT AND THE PLAN.  I HEREBY AGREE TO BE BOUND BY THE
     TERMS OF BOTH THIS AGREEMENT AND THE PLAN.  THE EFFECTIVENESS OF THIS
     AGREEMENT IS DEPENDENT UPON MY ELIGIBILITY TO PARTICIPATE IN THE PLAN.


DATE
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                                        SIGNATURE OF EMPLOYEE

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                                        PRINTED NAME



DURATION OF OPTION PERIOD:

FROM:            TO
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START DATE OF MY QUARTERLY              SUBSEQUENT QUARTERLY PERIODS
PERIOD OF PARTICIPATION:                OF PARTICIPATION:

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