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                                    SUBLEASE

     This  Sublease is entered into by and between  APPLIED  DIGITAL  ACCESS,  a
California  corporation,   Sublessor,   and  ENOVA  CORPORATION,   a  California
corporation,  Sublessee, under that certain Lease dated June, 1993, entered into
by Sorrento Tech Associates,  a California limited  partnership,  as Lessor, and
Sublessor  under this  Sublease  as Lessee,  as  amended by that  certain  First
Amendment to Lease dated as of September  23,  1994,  and as further  amended by
that certain Second Amendment to Lease dated as of August 8, 1996. A copy of the
Lease,  First  Amendment to Lease and Second  Amendment  to Lease,  collectively
hereinafter known as the Master Lease, are attached hereto as Exhibit "A."

1.       INCORPORATION OF AND ASSUMPTION
         OF MASTER LEASE OBLIGATIONS

Except as specifically provided in this Sublease to the contrary,  this Sublease
is subject  to all of the terms and  conditions  of the Master  Lease in Exhibit
"A." Except as specifically provided in this Sublease to the contrary, Sublessee
agrees to assume and perform the  obligations  of  Sublessor  and Lessee in said
Master Lease,  but only to the extent said  obligations  arise from or relate to
the Premises subleased pursuant to this Sublease.  Sublessee shall not commit or
permit to be committed on the Premises any act or omission  which shall  violate
any term or condition of the Master Lease.  In the event of the  termination  of
Sublessor's interest as Lessee under the Master Lease, for any reason, then this
Sublease  shall  terminate  coincidentally  therewith  without any  liability of
Sublessor  to  Sublessee,  subject  however to  Lessor's  agreement  to grant to
Sublessee  the quiet  enjoyment  of the  Premises  subleased  set forth below in
Lessor's Consent.

Sublessor and Sublessee  agree that  Sublessee  does not assume any  obligations
with regard to the following sections of the Master Lease:

Lease

2.5      Rentable Area Defined
2.6      Building Rentable Area
5        Additional Charges for Expenses
6.2      Security Deposit
7        Construction [Tenant Improvements]
16.2     Tenant's   Liability   Insurance   (Sublessee  will  provide  evidence
         of self-insurance)
16.3     Form of  Policies  (Sublessee  will  provide  evidence  of
         self-insurance)
18.6     Assumption of  Obligations
22.4     Payment of Sums Due
30.2     Financial Statements 30.10 Holding Over

First Amendment

3.          Security Deposit
5.          Brokers Commission



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Second Amendment

3.            Acceptance of Expansion Area
6.            Security Deposit
8.            Broker Commissions

2. PREMISES

Sublessor  leases to Sublessee and Sublessee  hires from Sublessor the following
described  Premises  together  with the  appurtenances  described  in the Master
Lease,  situated  in the  City of San  Diego,  County  of San  Diego,  State  of
California and described as:

9855 Scranton Road, Suite 100, approximately 23,381 square feet of Building 5 of
the San  Diego  Tech  Center  as  shown  on  Exhibit  "B"  attached  hereto  and
incorporated by this reference.

3. RENTAL

Sublessee  shall pay to  Sublessor  as rent for the  Premises  in advance on the
first day of each calendar month of the term of this Sublease without deduction,
offset, prior notice or demand, in lawful money of the United States, the sum of
Twenty-Seven   Thousand  One  Hundred   Twenty-One   Dollars   Ninety-Six  Cents
($27,121.96).  If the commencement date is not the first day of the month, or if
the  Sublessee  termination  date is not the last day of the  month,  a prorated
monthly  installment  shall be paid at the then current rate for the  fractional
month during which the Sublease commences and/or terminates.

In the event  Sublessee  continues to occupy the space after  September 1, 1997,
the monthly rental rate will be $28,291.01.  Sublessee  shall be responsible for
their separately metered electricity.

By executing this Sublease,  Sublessor hereby acknowledges receipt of $27,121.96
as the first month's rental.

4. TERM

     (a)  The  term  of  this  Sublease  shall  be for a  period  of six  months
commencing on January 1, 1997, and ending on June 30, 1997.

     (b) After  June 30,  1997  Sublessee  shall  have the  right to occupy  the
Premises on a month to month basis through December 31,1997,  and shall have the
right to  terminate  anytime  during that  period with thirty (30) days  written
notice.

     (c) In the event Sublessor is unable to deliver  possession of the Premises
at the  commencement  of the term,  Sublessor shall not be liable for any damage
caused  thereby,  and  this  Sublease  shall be  voidable  at  Sublessee's  sole
discretion. If the sublease is voided by Sublessee,



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Sublessee  shall not be liable for any rent due under the terms of the Sublease.
If  Sublessee,   with  Sublessor's  consent,   takes  possession  prior  to  the
commencement of the term,  Sublessee shall do so subject to all of the covenants
and conditions hereof except for the obligation to pay rent for the period prior
to and ending upon the commencement of the term as stated herein.

5.    USE

Sublessee  shall  use the  Premises  for  general  office  uses and for no other
purpose without the prior written consent of Sublessor,  which consent shall not
be unreasonably withheld.

6.    TENANT IMPROVEMENTS

Sublessee  shall accept the  premises in "as-is"  condition,  broom  clean.  Any
improvements  must be approved by Landlord and  Sublessor  per Section 10 of the
Master Lease.

7.    NOTICES

All notices or demands of any kind  required or desired to be given by Sublessor
or  Sublessee  thereunder  shall be in  writing  and shall be  deemed  delivered
forty-eight (48)hours after depositing the notice or demand in the United States
mail,  certified or registered,  postage prepaid,  addressed to the Sublessor or
Sublessee  respectively at the addresses set forth after their signatures at the
end of this  Sublease.  All rent and other payments due under the Sublease shall
be made by Sublessee to Sublessor at the same address.

Dated:  12/11/96                                  Dated:  12/9/96

             Sublessor:                           Sublessee:
             Applied Digital Access,              Enova Corporation,
             a California corporation             a California corporation


By:     /s/  Peter Savage                  By:   /s/  David R. Kuzma
             President                           Senior Vice President
             9855 Scranton Road                  101 Ash Street
             San Diego,  CA 92121                San Diego,  CA 92101


                                LESSOR'S CONSENT

The  undersigned,  Lessor under the Master Lease attached as Exhibit "A," hereby
consents to the  subletting  of the Premises  described  herein on the terms and
conditions  contained in this  Sublease.  This consent  shall apply only to this
Sublease and shall not be deemed to be a consent to any other  Sublease.  Lessor
hereby provides to Sublessee the right to remain in the subleased


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premises  under the same terms and  conditions set forth in this Sublease in the
event of Sublessor's default.

Dated: 12/12/96                            Lessor: Sorrento Tech Associates,
                                           a California limited partnership

                                           By: Barnes Canyon RPF Realty Corp.
                                           a Connecticut corporation,
                                           General Partner

                                           By: /s/ Mark S. Knapp
                                           Mark S. Knapp
                                           Vice President