Exhibit 10.3

                                 PROMISSORY NOTE

$175,000.00                                                          May 5, 2005

         For value  received,  Integrated  Security  Systems,  Inc.,  a Delaware
corporation  (hereinafter referred to as "Maker"),  promises to pay to the order
of Frost National Bank,  Custodian,  FBO Renaissance US Growth  Investment Trust
PLC,  Trust No.  W00740100,  a Texas  corporation  (hereinafter  referred  to as
"Payee"),  the  principal  sum of One  Hundred  Seventy  Five  Thousand  Dollars
($175,000.00).  The principal and interest on this Note shall be due and payable
in lawful money of the United States of America, c/o Security Processing T-8, P.
O. Box 2479,  San Antonio,  Texas  78298-2479.  All  correspondence  and notices
should be mailed to the above  address  with a copy to the  offices  of Payee at
8080 N. Central Expressway,  Suite 210, LB-59,  Dallas,  Texas 75206, or at such
other  place as the  holder  hereof may from time to time  designate  by written
notice to Maker.

         1.     Interest.  Interest shall accrue on the unpaid principal balance
due under this Note at an annual  rate  equal to eight  percent  (8%).  Interest
shall accrue from and including the date of this Note until,  but not including,
the day on which it is paid in full.  In no event  shall  the  interest  charged
hereunder  exceed the maximum rate of interest allowed from time to time by law.
Interest shall be due and payable  monthly on the first (1st) day of each month,
commencing June 1, 2005.

         2.     Payment of Note.  The  principal  balance  of,  and all  accrued
unpaid  interest  on, this Note shall be due and  payable on  November  11, 2007
except as otherwise provided herein. ("Maturity Date").

         3.     Prepayment.  This Note may be prepaid in whole or in part at any
time, at the option of Maker, without premium or penalty.

         4.     Default,  Enforcement.  Upon  default  in  payment of this Note,
Payee may pursue any and all rights and  remedies to which Payee may be entitled
under applicable law.

         5.     Limitation of Interest.  All agreements between Maker and Payee,
whether now  existing or  hereafter  arising  and whether  written or oral,  are
expressly  limited so that in no  contingency  or event  whatsoever,  whether by
reason of advancement of the proceeds  hereof,  acceleration  of the maturity of
the unpaid  balance  hereof,  or  otherwise,  shall the amount  contracted  for,
charged,  received,  paid or agreed to be paid to the holder hereof for the use,
forbearance, or detention of the money evidenced by this Note or for the payment
or  performance of any covenant or obligation  contained  herein or in any other
document  pertaining  to the  indebtedness  evidenced  by this Note  exceed  the
maximum  amount   permissible   under   applicable  usury  laws.  If,  from  any
circumstance  whatsoever,  fulfillment  of any provision  hereof or of any other
agreement  shall,  at the time  fulfillment  of such  provision be due,  involve
transcending the limit of validity  prescribed by law which a court of competent
jurisdiction may deem applicable hereto,  then, ipso facto, the obligation to be
fulfilled  shall  be  reduced  to the  limit of such  validity;  and if from any
circumstance  the holder  hereof  shall ever receive as interest an amount which
would exceed the maximum lawful rate, any amount equal to any excessive interest
shall (a) be  applied  to the  reduction  of the unpaid  principal  balance  due
hereunder  and not to the payment of  interest,  or (b) if such excess  interest
exceeds the unpaid principal balance of this Note, such excess shall be refunded
to Maker.  All sums contracted for,  charged or received  hereunder for the use,
forbearance  or detention of the  indebtedness  evidenced  hereby shall,  to the
extent permitted by applicable law, be amortized, prorated, allocated and spread
throughout  the full term of this note until payment in full so that the rate of
interest on account of such indebtedness is uniform  throughout the term hereof.
The terms and  provisions of this  paragraph  shall control and supersede  every
other provision of all agreements between Maker and the holder hereof.


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         6.     Waiver.  Except as otherwise  expressly  provided herein,  Maker
waives demand,  presentment for payment, notice of intent to accelerate,  notice
of acceleration,  notice of nonpayment or dishonor,  grace,  protest,  notice of
protest,  all other notices, and any and all diligence or delay in collection of
the filing of suit hereon.

         7.     Governing Law and Venue. This Note shall be construed  according
to and  governed  by the laws of the State of Texas.  The  obligations  of Maker
under this Note are performable in Dallas County, Texas.

         8.     Pledge Subordination. In order to secure full payment of amounts
due under this Note,  Maker  hereby  grants to Payee a security  interest in all
outstanding  capital  stock of the  following  subsidiaries  of Maker:  B&B ARMR
Corporation,  Intelli-Site,  Inc. and DoorTek Corporation (collectively referred
to as the "Pledged Stock"). However, such security interest shall be, and hereby
is,  subordinated to all liens,  pledges and security interests now or hereafter
granted to Briar Capital LLP ("Senior Lender") by Maker in connection with loans
from Senior Lender to Maker or its subsidiaries ("Senior Debt"), notwithstanding
the date of such lien.  Until the payment in full of the Senior Debt, Payee will
not seek to enforce against Maker any interest of Maker in the Pledged Stock.

         Senior  Lender may  dispose of any or all of Pledged  Stock free of any
and all security  interests and liens (after notice to Maker)  provided that the
entire proceeds  (after  deducting  reasonable  expenses of sale) are applied in
reduction  of the  Senior  Debt.  Maker  retains  all of its  rights as a junior
secured  creditor  with  respect to the surplus,  if any,  arising from any such
disposition of the Pledged Stock.

         9.     Successors and Assign.  This Note shall bind Maker's  successors
and assigns.

         10.    Collection  Costs. If this Note is collected by legal proceeding
or  through  a  probate  or  bankruptcy  court,  or is placed in the hands of an
attorney for  collection  after  default  (whether or not suit is filed),  Maker
agrees to pay all costs of collection and/or suit,  including but not limited to
reasonable attorneys' fees and expenses incurred by Payee.

         11.    Unenforceability.   The  invalidity,   or   unenforceability  in
particular circumstances,  of any provision of this Note shall not extend beyond
such provision or such circumstances,  and no other provision of this Note shall
be affected thereby.

         12.    Headings.  The  paragraph  headings of the sections of this Note
are inserted for  convenience of reference only and shall not affect the meaning
or interpretation of this Note.

         IN WITNESS WHEREOF, Maker has duly executed this note as of the day and
year first above written.

                                    INTEGRATED SECURITY SYSTEMS, INC.



                                    By:  /S/ C. A. RUNDELL, JR.
                                         ------------------------------------
                                         C. A. Rundell, Jr.
                                         Chairman and Chief Executive Officer




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