EXHIBIT 4.3


         THIS IS A  NON-TRANSFERABLE  NOTE.  THIS  NOTE HAS NOT BEEN  REGISTERED
         UNDER THE SECURITIES ACT OF 1933, AS AMENDED ("SECURITIES ACT"), OR ANY
         APPLICABLE STATE SECURITIES LAWS, AND MAY NOT BE OFFERED FOR SALE, SOLD
         OR OTHERWISE  TRANSFERRED EXCEPT PURSUANT TO AN EFFECTIVE  REGISTRATION
         STATEMENTS UNDER THE SECURITIES ACT AND ANY APPLICABLE STATE SECURITIES
         LAWS,  OR  PURSUANT  TO  AN  EXEMPTION  FROM  REGISTRATION   UNDER  THE
         SECURITIES ACT OR ANY APPLICABLE SECURITIES LAWS.


                             DEMAND PROMISSORY NOTE


$500,000.00                                                     October 14, 1999


ON DEMAND, for value received,  HYCOMP, INC., a corporation  organized under the
laws of the Commonwealth of Massachusetts (the "Maker"),  does hereby promise to
pay to the order of  SIMMONDS  CAPITAL  LIMITED,  an  Ontario  corporation  (the
"Holder"),  the principal  amount of FIVE HUNDRED THOUSAND UNITED STATES DOLLARS
(U.S. $500,000.00), together with interest on the unpaid principal amount hereof
from time to time outstanding at the rate of 8% per annum  compounded  quarterly
commencing  on the date hereof to the date of maturity or  accelerated  maturity
and thereafter at the rate of 12% compounded quarterly.

This Note has been executed and delivered pursuant to a Stock Purchase Agreement
dated as of October 14, 1999 (the "Stock Purchase Agreement"), between the Maker
and the Holder.  Interest on the Note shall be payable  quarterly  in arrears on
the last  business day of each calendar  quarter and at maturity or  accelerated
maturity, and following maturity or accelerated maturity.

1. Payments of Principal Amount. The entire principal amount hereof shall be and
payable on the date that is the earlier of (i)  October 14, 2000 (the  "Maturity
Date"),  or (ii) the date upon which  indebtedness  becomes  immediately due and
payable by reason of any of the following:

(a)  consummation  of an  offering  by the  Holder of either  its equity or debt
securities for cash,  which,  together with all such other  offerings of debt or
equity securities  occurring from and after the date hereof,  shall total in net
amount of proceeds to the Maker an amount equal or exceeding $1,000,000; or

(b) the  default  by Maker in the  payment  of any  amount of  interest  payable
hereunder  when due and such  default  shall  continued  for a period of 15 days
after written demand therefor by the Holder; or

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                  (c)  the  occurrence  of  an  event  of  default  ("Events  of
Default"), as described in Section 2 below.

         Section 2. Events of Default.  Without  limiting any of the above,  the
Holder may, by written notice to Maker,  declare this Note  immediately  due and
payable, whereupon this Note and all sums due hereunder shall become immediately
due and payable without protest, presentment, demand or notice, all of which are
expressly waived by Maker, if any of the following Events of Default occur:

                  (a) principal, interest or any other amount due under the Note
shall not be paid as and when due (after any applicable  grace period),  whether
at maturity, by declaration or otherwise;

                  (b) Maker shall become  insolvent or any  proceeding  shall be
instituted by the Maker seeking relief on its behalf as debtor, or to adjudicate
it a bankrupt, or insolvent, or seeking reorganization,  arrangement, adjustment
or  composition  of it or its  debts  under  any  law  relating  to  bankruptcy,
insolvency or reorganization or relief of debtors,  or seeking  appointment of a
receiver,  trustee,  custodian  or  other  similar  official  for it or for  any
substantial  part of its property or Maker shall  consent by answer or otherwise
to the institution of any such proceeding against it;

                  (c) any proceeding is instituted  against the Maker seeking to
have an order for  relief  entered  against it as debtor or to  adjudicate  it a
bankrupt or insolvent,  or seeking  reorganization,  arrangement,  adjustment or
composition of it or its debts under any law relating to bankruptcy, insolvency,
or  reorganization or relief to debtors,  or seeking  appointment of a receiver,
trustee,  custodian or other similar official for it or for any substantial part
of its  property  which  either  (i)  results  in any such entry of an order for
relief,  adjudication  or  bankruptcy  or insolvency or issuance or entry of any
other order having a similar effect or (ii) remains  undismissed for a period of
thirty (30) days;

                  (d) a receiver,  trustee or other  custodian is appointed  for
any substantial part of Maker's assets;

                  (e)  any  assignment  is  made  for  the  benefit  of  Maker's
creditors; or

                  (f) the dissolution or other winding up of Maker.

         3. Prepayment.  This Note may be prepaid by Maker, in whole or in part,
at any time without  penalty,  provided  that any such payment  shall be applied
first to the  payment  of accrued  but unpaid  interest  and  thereafter  to the
outstanding principal.

         4.  Certain  Costs  and  Expenses.  Maker  agrees  to pay all  expenses
incurred by the Holder hereof in connection  with the collection and enforcement
of this Note,  including,  without  limitation,  reasonable  attorneys' fees and
disbursements.

         5. Certain Payment Provisions. All payments shall be made to the Holder
at its  offices  located at 580  Granite  Court,  Pickering,  Ontario,  L1W 3Z4,
CANADA,  or such other  location  as the Holder  shall  designate  in writing to
Maker.  Whenever any payment to be made

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<PAGE>

hereunder  shall be stated to be due on a day that is not a Business  Day,  such
payment  shall be due  instead on the next  succeeding  Business  Day,  and such
extension  of time shall in such case be  included  in the  computation  of such
payment of interest  and not in the  computation  of the  succeeding  payment of
interest. For the purposes of this Note, the phrase "Business Day" means any day
that is not a Saturday,  Sunday or a legal holiday on which banks are authorized
or required to be closed in New York, New York.

                  6.  Waivers.  Maker  hereby  waives  diligence,   presentment,
protest and notice of any kind,  forbearance or other indulgence,  and agrees to
pay all costs of collection when incurred, including reasonable attorney's fees,
and to perform and comply with each of the covenants, conditions, provisions and
agreements  contained  in every  instrument  evidencing  said  indebtedness.  No
extension of the time for payment of this Note made by agreement with any person
now or hereafter  liable for the payment of this Note shall  operate to release,
discharge,  modify,  change or affect the  original  liability  under this Note,
either  in whole or in part,  of the Maker  unless  Holder  and  Maker  shall be
parties to such agreement.

                  7.  Modifications;  Amendments.  This Note may not be changed,
modified or terminated orally, but only by an agreement in writing signed by the
party to be charged.

                  8. Assignments.  This Note shall be binding upon the Maker and
its  successors and assigns and for the benefit of the Holder and his successors
and  assigns.  The rights of the Holder and the  obligations  of the Maker under
this Note may not be assigned, modified, altered, amended, terminated or waived,
except in writing signed by the Maker and the Holder.

                  9. Governing Law. This Note shall be governed by and construed
in  accordance  with the laws of the  State of New York,  without  regard to the
principles  of conflict of laws  thereof.  If a provision  of this Note shall be
held invalid, illegal or unenforceable, the validity of all the other provisions
herein shall in no way be affected thereby.

                  10. Jurisdiction; Venue. The Maker irrevocably consents to the
jurisdiction  of the  courts of the State of New York and of any  federal  court
located in such State in connection with any action or proceeding arising out of
or relating to this Note, any document or instrument  delivered  pursuant to, in
connection  with or  simultaneously  with this Note, or a breach of this Note or
any such document or  instrument.  In any such action or  proceeding,  the Maker
waives  personal  service of any summons,  complaint or other process and agrees
that service  thereof may be made in accordance  with the applicable  provisions
for service of process by mail set forth in the New York Civil Practice Laws and
Rules.

                  11. Waiver of Jury Trial.  Maker hereby irrevocably waives all
rights to trial by jury in any action, proceeding or counterclaim (whether based
on contract,  tort or otherwise)  arising out of or relating to this Note or the
negotiation, administration, performance or enforcement hereof.

                  12. Severability.  If any item or provision of this Note shall
be held invalid,  illegal or unenforceable,  the validity of all other terms and
provisions herein shall in no way be affected thereby.

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<PAGE>


                  IN WITNESS WHEREOF, the Maker has caused this instrument to be
duly executed this 14th day of October, 1999.

                                          HYCOMP, INC.

                                          By: /s/ Paul K. Hickey
                                             ----------------------------------
                                          Name:  Paul K. Hickey
                                          Title: Chairman and Chief Executive
                                                 Officer


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