EXHIBIT 10.52

                                 PROMISSORY NOTE

$ 425,000.00                                                   December 14, 2001

For  valuable  consideration,  the receipt and  sufficiency  of which are hereby
acknowledged,  the  undersigned  VERTICAL  COMPUTER  SYSTEMS,  INC.,  a Delaware
corporation  ("Borrower"),  promises to pay to the order of BRIGHTON OPPORTUNITY
FUND,  LP  ("Lender"),  in lawful  money of the  United  States of  America  the
principal amount of FOUR HUNDRED  TWENTY-FIVE  Thousand Dollars ($425,000 U.S.),
together with interest on the amount of such principal  outstanding from time to
time at the rate of twelve percent (12%) per annum, calculated on the basis of a
three hundred sixty (360) day year containing  twelve (12) months of thirty (30)
days each (the "Basic Interest  Rate"),  at the times and in the manner provided
herein.

1. PAYMENT OF PRINCIPAL  AND INTEREST.  Principal and interest  shall be paid as
follows:

      a. An interest  payment for interest accrued during the period that begins
on the date Borrower actually receives the loan from Lender and ends on December
31, 2001 shall be payable on December 31, 2001.

      b. The principal, and all interest, fees, charges, and other amounts owing
hereunder  and then  unpaid  shall be due and  payable on January  31, 2002 (the
"Maturity Date").

      c.  Borrower  shall pay all amounts  owing under this Note in  immediately
available  funds to Lender at Lender's  address as set forth herein,  or at such
other place as may be specified in writing by Lender.  Each payment,  when made,
shall be credited  first to interest  then due, and then at the option of Lender
to principal, late charges, and other fees and expenses outstanding hereunder in
such order as Lender may  determine.  Payments  received  after 1:00 p.m. on any
banking day or at any time on any Saturday,  Sunday,  or holiday shall be deemed
received on the next banking day.

2.  COLLATERAL AS SECURITY.  This Note is secured by certain  collateral,  which
encumbers,  among other things,  the interest of Borrower in certain assets,  as
more particularly described therein (the "Collateral").  This Note and the Stock
Pledge   Agreements  of  even  date  herewith,   between  Lender  and  Pledgors,
respectively,  Mountain  Reservoir  Corporation  and Luiz Valdetaro (the "Pledge
Agreements")  and  Lender of even date  herewith,  and any  other  documents  or
instruments given or to be given to Lender to secure the indebtedness  evidenced
by this Note are collectively  referred to herein as the "Loan  Documents".  The
Company  under no  circumstances  will cancel the stock being held as Collateral
unless required to do so by a state or federal regulatory body.

3.  INTEREST  RATE UPON  DEFAULT.  Should  Borrower fail to pay any amount owing
hereunder as and when due,  whether the same is due regularly as scheduled or by

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reason of  acceleration  following  default or otherwise,  then  interest  shall
accrue on the past due amount at the Basic Interest Rate. Such interest shall be
due and  payable  upon the  earlier  of demand or the first day of the  calendar
month following the month in which the same shall have accrued.

4. DEFAULT;  REMEDIES.  Each of the following  occurrences and conditions  shall
constitute an Event of Default:

      a.  failure  of  Borrower  to pay as  and  when  due  any  money,  whether
principal,  interest, or otherwise, under this Note, or the breach or default of
any obligation to pay money under or secured by the Stock Pledge Agreement; or

      b. failure of Borrower to perform any obligation  other than an obligation
to pay money, as and when  performance of such obligation is due under this Note
or Loan  Documents  which  failure  continues for fifteen (15) days after notice
thereof from Lender to Borrower; or

      c.  failure  by  Borrower  to comply  with any of the  terms,  provisions,
covenants,  conditions or restrictions now or hereafter affecting the Collateral
or any part thereof or contained in any  agreement  related or pertaining to the
Collateral,  which failure  continues for fifteen (15) days after notice thereof
from Lender to Borrower; or

      d.  Borrower's  making  or at any time  having  made  any  representation,
warranty or disclosure to Lender that is or was  materially  false or misleading
on the date as of which made,  whether or not that  representation or disclosure
appears in the Loan Documents; or

      e. the sale, transfer,  conveyance,  or lease of all or any portion of the
Collateral  or  of  any  of  Borrower's  rights  therein,  whether  voluntarily,
involuntarily,  or otherwise, or Borrower's entering into an agreement to do any
of the foregoing, in each case except as expressly permitted in the Stock Pledge
Agreement; or

At any time following the occurrence of any Event of Default, or following the
occurrence of any event as a consequence of which the obligations evidenced
hereby may be accelerated, then at the election of Lender and notwithstanding
anything to the contrary herein or elsewhere, the entire amount of principal
then outstanding under this Note and all interest, fees, charges, and other
amounts owing and then unpaid hereunder shall become immediately due and
payable, and Lender may exercise any and all rights that it may have under the
Loan Documents, at law, in equity, and otherwise. In the event of a default on
the Promissory Note where (a) the stock is sold pursuant to the Stock Pledge
Agreements by MRC and Valdetaro and (b) the proceeds of these sales of stock are
is insufficient to cover the principle and any interest then owed pursuant to
the Note, Vertical acknowledges and agrees that it will be liable for any then
outstanding amounts.


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5.  ATTORNEYS'  FEES.  Borrower  shall pay to Lender  upon  demand all costs and
expenses  incurred by Lender in connection with  determination,  protection,  or
enforcement of any and all of Lender's rights hereunder or under any of the Loan
Documents,  including  enforcement  of  any  and  all  obligations  of  Borrower
hereunder and  thereunder  and  protection,  enhancement,  or maintenance of the
security  interests  securing such obligations or the priority of the same. Such
costs and expenses shall be payable  whether or not any suit is instituted,  and
the same shall include without limitation  attorneys' fees, expert witness fees,
costs of  investigation,  and all of such costs incurred in connection  with any
trial, appellate proceeding,  or any case or proceeding under Chapters 7, 11, or
13 of the Bankruptcy Code or any successor thereto.

6. WAIVER OF NOTICE.  Borrower and each  endorser,  guarantor and surety of this
Note  hereby  waive  diligence,  demand,  presentment  for  payment,  notice  of
discharge, notice of nonpayment, protest and notice of protest, and specifically
consent to and waive notice of any renewals or extensions of this Note,  whether
made to or in favor of Borrower or any other  person or  persons.  Borrower  and
each endorser,  guarantor and surety of this Note further waive and renounce all
rights  to the  benefits  of all  statutes  of  limitation  and any  moratorium,
appraisement,  by any federal exception and homestead now or hereafter  provided
or state law or statute,  including but not limited to exemptions provided by or
allowed under the Bankruptcy Code, both as to each of themselves  personally and
as to all of their property,  whether real or personal,  against the enforcement
and  collection  of the  obligations  evidenced  by  this  Note  and any and all
extensions, renewals and modifications thereof.

7. NOTICES.  All notices  required  hereunder or  pertaining  hereto shall be in
writing  and shall be deemed  delivered  and  effective  upon the earlier of (i)
actual  receipt,  or (ii) the date of  delivery or refusal of the  addressee  to
accept  delivery  if such  notice is sent by express  courier  service or United
States mail, postage prepaid, certified or registered, return receipt requested,
in either case to the applicable address as follows:

To Lender:                 David Firestone
                           Brighton Opportunity Fund, LP
                           1801 Century Park East, Ste 1235
                           Los Angeles, CA 90067

To Borrower:               VERTICAL COMPUTER SYSTEMS, INC.
                           6336 Wilshire Boulevard
                           Los Angeles, CA 90048
                           Attn: President

Notwithstanding  the  foregoing,  any  notice  under or  pertaining  to the Loan
Documents or the  obligations  secured thereby given and effective in accordance
with  applicable  law shall be effective for purposes  hereof.  Either party may
change  the  address  at which it is to  receive  notices  hereunder  to another
business  address within the United States (but not a post office box or similar

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mail  receptacle)  by giving  notice of such  change of  address  in  accordance
herewith.

9. EXERCISE OF RIGHTS. No single or partial exercise of any of Lenders rights or
powers  under this Note or any of the other Loan  Documents  shall  preclude any
other or further  exercise  thereof or the exercise of any other right or power.
Lender at all times  shall have the right to proceed  against any portion of the
security  which secures  payment of the  indebtedness  evidenced  hereby in such
order and manner as Lender may elect without  waiving any rights with respect to
any other portion of such  security.  Each and all rights and remedies of Lender
hereunder and under the Loan  Documents are  cumulative  and in addition to each
and all other such rights and remedies. No exercise of any right or remedy shall
preclude exercise of any other right or remedy.

10. NO WAIVER.  No failure of Lender to insist  upon strict  performance  of any
obligation of Borrower or to exercise any right or remedy hereunder or under the
Loan Documents,  whether before or after any default,  shall  constitute or give
rise to a waiver thereof, and no waiver of any default shall constitute a waiver
of any future default or of any other default. No failure to accelerate the debt
evidenced hereby by reason of default hereunder or otherwise,  and no acceptance
of any past due  payment  hereunder  or  acceptance  of any amount less than the
amount then due, and no other indulgence that may be granted by Lender from time
to time shall (a)  preclude  the  exercise  of any right that Lender may have at
law, in equity, by contract or agreement or otherwise, or (b) constitute or give
rise to (i) a waiver of such right of acceleration or any other right, or (ii) a
novation of this Note or a reinstatement of the debt evidenced  hereby, or (iii)
any waiver of  Lender's  rights to demand and  receive  from  Borrower  full and
prompt payment and performance thereafter, to impose late charges retroactively,
or to declare a default.  Borrower and each endorser,  guarantor,  and surety of
this Note  hereby  expressly  waive the benefit of any statute or rule of law or
equity which would produce any result  contrary to or otherwise in conflict with
any of the foregoing.

11. ASSIGNMENT;  SUCCESSORS AND ASSIGNS. Lender may assign or otherwise transfer
all or any part of its interest  herein.  Promptly  following  written notice of
such  assignment  or other  transfer,  duly executed by Lender,  Borrower  shall
render full and complete performance hereunder as and when due to the transferee
so designated by Lender. Borrower shall not assign or transfer all or any of its
interests or obligations hereunder, and any attempted or purported assignment or
transfer  by  Borrower  shall be void and of no force or  effect,  except to the
extent  that  the  same  may be  expressly  permitted  under  the  Stock  Pledge
Agreements.  Subject to the foregoing, the terms of this Note shall apply to, be
binding  upon,  and  inure  to the  benefit  of ail  parties  hereto  and  their
successors and assigns.

12.  MODIFICATION.  This Note shall not be  modified,  amended,  or  terminated,
except by written  agreement  duly  executed  and  delivered  by both Lender and
Borrower.

13.  CONFLICTS.  In the event of any conflict between any provision of this Note
and  any  provision  of the  Stock  Pledge  Agreements,  which  conflict  cannot

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reasonably be resolved in such a way as to give effect to all provisions  herein
and therein contained, this Note shall govern.

14. SEVERABILITY.  If any provision of this Note or any payments pursuant to the
terms hereof shall be invalid or unenforceable  to any extent,  the remainder of
this Note and any other  payments  hereunder  shall not be affected  thereby and
shall be enforceable to the greatest extent permitted by law.

15.  GOVERNING  LAW.  This Note shall be governed by and construed in accordance
with the laws of the State of California.

      IN WITNESS  WHEREOF,  Borrower has executed and delivered  this Note as of
the date first written above.

                                              VERTICAL COMPUTER SYSTEMS, INC.



                                              By
                                                --------------------------------
                                                  Richard Wade, President




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