REVOLVING CREDIT NOTE

$28,000,000                                              Santa Clara, California
                                                                   July 17, 1996

     FOR  VALUE  RECEIVED,  the  undersigned  promises  to pay to the  order  of
COMERICA  BANK-CALIFORNIA  (the  "Bank") at 333 Santa  Clara  Street,  San Jose,
California,  on July 1, 1998,  the principal sum or so much of the principal sum
of Twenty Eight Million Dollars ($28,000,000) as may from time to time have been
advanced and be outstanding  under that certain Loan  Agreement  dated March 31,
1994 between the undersigned and the Bank (the "Agreement") plus all accrued but
unpaid interest thereon.

     The unpaid  principal  amount of this Note shall bear  interest at the rate
provided  in  Section  2.4.1 of the  Agreement,  which  Agreement,  as it may be
amended from time to time, is by this reference  incorporated  herein and made a
part hereof. Interest shall be payable to the extent accrued on the first day of
each  consecutive  calendar  month,  beginning  August 1, 1996,  until  maturity
(whether by  acceleration  or otherwise)  and,  thereafter,  on demand at a rate
equal to  three  percent  (3%) per  annum  plus  the rate  otherwise  prevailing
hereunder,  but in no  event  to  exceed  the  Legal  Rate  (as  defined  in the
Agreement).

     This Note is a Master Note under which sums may or must be repaid from time
to time and under which new advances are to be made by the Bank  pursuant to the
terms and  conditions  of the  Agreement,  and the books and records of the Bank
shall constitute the best evidence of the amount of the indebtedness at any time
owing hereunder.

     This Note is secured by the Collateral described in the Agreement, to which
reference is made for, among other things,  the conditions under which this Note
may or must be paid in  whole  or in part  prior to its due date or its due date
accelerated.  The Bank is hereby granted a security  interest in all property of
the  undersigned  at any time in the possession of the Bank or any Affiliate (as
defined in the  Agreement) of the Bank (or as to which the Bank or any Affiliate
of the Bank at any time controls possession by documents or otherwise).

     If an Event of  Default  (as  defined in the  Agreement)  occurs and is not
cured  within the time,  if any,  provided  for by the  Agreement,  the Bank may
exercise any one or more of the rights and remedies  granted by the Agreement or
any document  contemplated  thereby or given to a secured party under applicable
law,  including  without limit the right to  accelerate  this Note and any other
Indebtedness  (as  defined  in the  Agreement),  and  may set  off  against  the
principal of and interest on this Note or against any other Indebtedness (i) any
amount  owing  by  the  Bank  to  the  undersigned,  (ii)  any  property  of the
undersigned  at any time in the  possession  of the Bank or any Affiliate of the
Bank.

     The undersigned and all accommodation parties, guarantors and indorsers (i)
waive presentment,  demand,  protest and notice of dishonor,  (ii) agree that no
extension or indulgence to the undersigned or release or  non-enforcement of any
security,  whether with or without  notice,  shall affect the obligations of any
accommodation  party,  guarantor or indorser,  and (iii) agree to reimburse  the
holder of this note for any and all costs and expenses incurred in collecting or



<PAGE>

attempting  to  collect  any and all  principal  and  interest  under  this Note
(including,  but not  limited  to,  court costs and  reasonable  attorney  fees,
whether  in-house or outside counsel is used and whether such costs and expenses
are  incurred  in formal or  informal  collection  actions,  federal  bankruptcy
proceedings,  appellate proceedings,  probate proceedings,  or otherwise).  This
Note shall be governed by and construed in accordance with the laws of the State
of California.

     IN WITNESS  WHEREOF,  the undersigned has executed this Note as of July 17,
1996.

                                                   Zycon Corportion



                                                   By:  /s/ Ronald H. Donati
                                                   -----------------------------
                                                       Ronald H. Donati
                                                       President