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                           FIRST AMENDMENT TO SUBLEASE

     THIS FIRST AMENDMENT TO SUBLEASE  ("Amendment") is made as of this 24th day
of January 1997, by and between APPLIED DIGITAL ACCESS, a California corporation
("Sublessor"),  and ENOVA CORPORATION,  a California corporation  ("Sublessee"),
with  reference  to that  certain  Sublease  being  entered  into by and between
Sublessor  and  Sublessee  concurrently  herewith  and  executed by Sublessee on
December 9, 1996  ("Sublease").  For the  purposes of this  Amendment,  the term
"Sublease"  shall mean,  collectively,  the Sublease and this  Amendment and the
capitalized  terms used herein shall have the  meanings  ascribed to them in the
Sublease unless otherwise indicated.  Except as modified as provided herein, the
Sublease shall remain in full force and effect.  To the extent that there is any
conflict  between  this  Amendment  and the  Sublease,  the  provisions  of this
Amendment shall prevail.

     NOW, THEREFORE, in consideration of covenants,  terms and conditions herein
set forth and for other good, valuable and sufficient consideration,  receipt of
which is hereby acknowledged, the parties hereto agree as follows:

     1. MASTER  LANDLORD'S  OBLIGATIONS.  It shall be the  obligation  of Master
Landlord to (i) provide or cause to be provided  all  services and repairs to be
provided by Landlord under the terms of the Master Lease and (ii) to satisfy all
obligations and covenants of Master Landlord made in the Master Lease. Sublessee
acknowledges that Sublessor's obligation to perform services, provide utilities,
make repairs and carry  insurance shall be satisfied only to the extent that the
Master  Landlord  under the  Master  Lease  satisfies  those  same  obligations;
provided, however, Sublessor, upon written notice by Sublessee, shall diligently
attempt to enforce all obligations of Master Landlord under the Master Lease.

     2. LATE PAYMENT  CHARGES AND INTEREST.  Any payment of rent or other amount
from Sublessee to Sublessor under the Sublease which is not paid within 10 (ten)
days from the date due shall  accrue  interest  from the date due until the date
paid at a rate equal to ten percent (10%) per year; provided, however, that if a
court of competent  jurisdiction  determines  the above rate exceeds the highest
lawful rate of  interest,  then at the  maximum  rate  permitted  by law. If any
installment of rent for the subleased Premises is not paid promptly on the first
of the month,  or otherwise  when due,  Sublessee  shall pay to Sublessor a late
payment  charge  equal to five  percent  (5%) of the  amount of such  delinquent
payment of rent, in addition to the installment of rent then owing. This Section
3 shall not relieve Sublessee of Sublessee's  obligation to pay any amount owing
hereunder at the time and in the manner provided.

     3. USE -- COMPLIANCE WITH LAWS. At its own expense, Sublessee will procure,
maintain  in effect  and  comply  with all  conditions  of any and all  permits,
licenses  and  other   governmental  and  regulatory   approvals   required  for
Sublessee's use of the Subleased Premises.

     4. ASSIGNMENT AND SUBLETTING.  Sublessee shall not sell, assign,  encumber,
sublease or otherwise  transfer by operation of law or otherwise  the  subleased
Premises or the Sublease without Sublessor's consent,  which consent, based upon
the short term  nature of this  Sublease,  may be  withheld  or  conditioned  by
Sublessor  in its sole and  arbitrary  discretion.  Any such  sale,  assignment,
encumbrance,  sublease  or  other  transfer  in  violation  of the  terns of the
Sublease shall be void and shall be of no force or effect.

     5.  INDEMNITY.  Except to the extent  caused by the  negligence  or willful
misconduct  of the  Master  Landlord,  the  "Related  Parties"  (as  defined  in
Paragraph 22.2 of the Master Lease), and/or Sublessor, Sublessee will indemnify,
defend (by counsel  reasonably  acceptable  to  Sublessor  and which may include
in-house  attorneys),  protect and hold Sublessor  harmless from and against any
and all  liabilities,  claims,  demands,  losses,  damages,  costs and  expenses
(including  attorneys'  fees) arising out of or relating to those items referred
to in Section  22.2 (a)  through  (g) of the Master  Lease or arising  out of or
related  to  any  breach  or  default  under  the  Master  Lease  caused  by the
Sublessee's breach or default under the sub-lease.



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     6. BROKERAGE COMMISSION. Each party warrants to the other that there are no
brokerage  commissions or fees payable in connection with the Sublease except to
Colliers Iliff Thorn and Sentre Partners. Each party also agrees that payment of
the  brokerage  commissions  will be made by the  Sublessor.  Each party further
agrees to indemnify and hold the other party harmless,  from any cost, liability
and expense  (including  attorneys' fees) which the other party may incur as the
result of any claim for a fee or  commission  by any  broker or finder  claiming
through the indemnifying patty in connection with this Sublease.

     7.  ATTORNEYS'  FEES.  In the event  either party shall bring any action or
proceeding  for  damages  or for an  alleged  breach  of  any  provision  of the
Sublease,  to recover  rents or to enforce,  protect or  establish  any right or
remedy under the  Sublease,  the  prevailing  party shall be entitled to recover
reasonable attorneys' fees and court costs as part of such action or proceeding.

     IN WITNESS WHEREOF, the parties hereto have executed one (1) or more copies
of this Sublease, effective as of the last date written below.

"SUBLESSOR"                                   "SUBLESSEE"

APPLIED DIGITAL ACCESS,                    ENOVA CORPORATION,
a California corporation                   a California corporation

/S/ JAMES KEEFE                            /S/ DAVID R. KUZMA
James Keefe, Chief Financial Officer       David R. Kuzma, Senior Vice President




ACCEPTED AND AGREED TO:


"LANDLORD"

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 Presiden