EXHIBIT 10.21

THIS  SECURED  CONVERTIBLE  DEBENTURE,  AND  THE  SECURITIES  INTO  WHICH  IT IS
CONVERTIBLE (COLLECTIVELY, THE "SECURITIES"),  HAVE NOT BEEN REGISTERED WITH THE
UNITED STATES SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF
ANY STATE.  THE  SECURITIES  ARE BEING  OFFERED  PURSUANT  TO A SAFE HARBOR FROM
REGISTRATION UNDER REGULATION D PROMULGATED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE "ACT").  THE SECURITIES ARE  "RESTRICTED" AND MAY NOT BE OFFERED OR
SOLD UNLESS THE SECURITIES ARE REGISTERED UNDER THE ACT,  PURSUANT TO REGULATION
D OR PURSUANT TO AVAILABLE EXEMPTIONS FROM THE REGISTRATION  REQUIREMENTS OF THE
ACT AND THE  COMPANY  WILL BE  PROVIDED  WITH  OPINION  OF COUNSEL OR OTHER SUCH
INFORMATION  AS IT MAY  REASONABLY  REQUIRE TO CONFIRM THAT SUCH  EXEMPTIONS ARE
AVAILABLE. FURTHER HEDGING TRANSACTIONS INVOLVING THE SECURITIES MAY NOT BE MADE
EXCEPT IN COMPLIANCE WITH THE ACT.



                          SECURED CONVERTIBLE DEBENTURE

                   ADVANCED COMMUNICATIONS TECHNOLOGIES, INC.

                        10% SECURED CONVERTIBLE DEBENTURE

                              DUE NOVEMBER 22, 2004


No.  ___                                                          $250,000.00

      This Secured  Convertible  Debenture is issued by ADVANCED  COMMUNICATIONS
TECHNOLOGIES,  INC., a Florida  corporation (the "COMPANY"),  to Cornell Capital
Partners,  LP (together with its permitted successors and assigns, the "HOLDER")
pursuant to exemptions  from  registration  under the Securities Act of 1933, as
amended.

      THIS DEBENTURE IS FREE FROM ALL TAXES, LIENS, CLAIMS AND ENCUMBRANCES WITH
RESPECT TO THE ISSUE  THEREOF AND SHALL NOT BE SUBJECT TO  PREEMPTIVE  RIGHTS OR
OTHER SIMILAR RIGHTS OF STOCKHOLDERS OF THE COMPANY AND WILL NOT IMPOSE PERSONAL
LIABILITY UPON THE HOLDER.  THE  OBLIGATIONS OF THE COMPANY UNDER THIS DEBENTURE
SHALL BE SECURED BY THAT  CERTAIN  SECURITY  AGREEMENT  DATED BY AND BETWEEN THE
COMPANY AND THE HOLDER OF EVEN DATE HEREWITH.

<PAGE>

                                   ARTICLE I.

      Section 1.01  PRINCIPAL AND INTEREST.  For value  received on November 22,
2002,  the Company  hereby  promises to pay to the order of the Holder in lawful
money of the United  States of America and in  immediately  available  funds the
principal sum of Two Hundred Fifty Thousand Dollars (US  $250,000.00),  together
with  interest  on the unpaid  principal  of this  Debenture  at the rate of ten
percent  (10%) per year  (computed on the basis of a 365-day year and the actual
days  elapsed)  from the date of this  Debenture  until paid.  At the  Company's
option, the entire principal amount and all accrued interest shall be either (a)
paid to the Holder on the second (2nd) year  anniversary from the date hereof or
(b) converted in accordance with Section 1.02 herein.

      Section 1.02  OPTIONAL  CONVERSION.  After  December 15, 2002, or upon the
earlier breach by the Company of this Debenture or any other  agreement with the
Holder, the Holder shall be entitled, at its option, to convert, and sell on the
same  day,  at any time and from  time to time,  until  payment  in full of this
Debenture,  all or any  part of the  principal  amount  of the  Debenture,  plus
accrued interest,  into shares (the "CONVERSION SHARES") of the Company's common
stock,  no par value per share  ("COMMON  STOCK"),  at the price per share  (the
"CONVERSION  PRICE") equal to $.001. No fraction of shares or scrip representing
fractions  of  shares  will be issued on  conversion,  but the  number of shares
issuable shall be rounded to the nearest whole share. To convert this Debenture,
the Holder hereof shall deliver  written notice  thereof,  substantially  in the
form  of  EXHIBIT  "A" to  this  Debenture,  with  appropriate  insertions  (the
"CONVERSION  NOTICE"),  to the Company at its address as set forth  herein.  The
date upon which the conversion shall be effective (the "CONVERSION  DATE") shall
be deemed to be the date set forth in the Conversion Notice.

      Section 1.03 RIGHT OF REDEMPTION.  Until February 22, 2003, the Company at
its option shall have the right to redeem,  upon written notice (the "REDEMPTION
NOTICE"),  a portion or all outstanding  convertible  debenture.  The redemption
price shall be one hundred  twenty  percent  (120%) of the amount  redeemed plus
accrued interest.  After December 15, 2002, the Company at its option shall have
the right to redeem, upon written notice (the "REDEMPTION NOTICE"), a portion or
all outstanding convertible debenture. The redemption price shall be one hundred
fifty  percent  (150%) of the amount  redeemed plus accrued  interest.  Once the
Company has issued to the Holder a Redemption  Notice the Holder may continue to
execute  conversions  only as long as the  closing  bid  price of the  Company's
Common Stock the day prior to  conversion  is above the Closing Bid Price of the
Company's Common Stock on the Closing Date.

      Section 1.04  RESERVATION  OF COMMON STOCK.  The Company shall reserve and
keep available out of its authorized but unissued shares of Common Stock, solely
for the purpose of effecting the  conversion of this  Debenture,  such number of
shares of Common Stock as shall from time to time be  sufficient  to effect such
conversion, based upon the Conversion Price. If at any time the Company does not
have a sufficient number of Conversion Shares authorized and available, then the
Company shall call and hold a special meeting of its stockholders  within ninety
(90)  days of that  time  for the sole  purpose  of  increasing  the  number  of
authorized shares of Common Stock.

                                       2
<PAGE>

      Section 1.05 REGISTRATION RIGHTS. The Company is obligated to register the
resale of the  Conversion  Shares under the  Securities Act of 1933, as amended,
pursuant to the terms of a Registration  Rights  Agreement,  between the Company
and  the  Holder  of even  date  herewith  (the  "INVESTOR  REGISTRATION  RIGHTS
AGREEMENT").

      Section 1.06  INTEREST  PAYMENTS.  The interest so payable will be paid at
the time of maturity or conversion to the person in whose name this Debenture is
registered.  At the time such  interest is  payable,  the  Company,  in its sole
discretion,  may elect to pay  interest in cash (via wire  transfer or certified
funds) or in the form of Common Stock. In the event of default,  as described in
Article III Section  3.01  hereunder,  the Holder may elect that the interest be
paid in cash (via wire transfer or certified funds) or, after December 15, 2002,
in the form of Common Stock. If paid in the form of Common Stock,  the amount of
stock to be issued  will be based on a  conversion  price of $.001 per share.  A
number of shares of Common  Stock with a value  equal to the amount of  interest
due shall be issued.  No  fractional  shares will be issued;  therefore,  in the
event  that the value of the  Common  Stock  per share  does not equal the total
interest due, the Company will pay the balance in cash.

      Section 1.07 PAYING AGENT AND REGISTRAR.  Initially,  the Company will act
as paying  agent and  registrar.  The  Company  may  change  any  paying  agent,
registrar,  or  Company-registrar  by giving  the  Holder not less than ten (10)
business  days' written  notice of its election to do so,  specifying  the name,
address, telephone number and facsimile number of the paying agent or registrar.
The Company may act in any such capacity.

      Section 1.08  SUBORDINATED  NATURE OF  DEBENTURE.  This  Debenture and all
payments  hereon,  including  principal or interest,  shall be  subordinate  and
junior in right of payment to all  accounts  payable of the Company  incurred in
the  ordinary  course of business  and/or bank debt of the Company not to exceed
$250,000.

                                  ARTICLE II.

      Section  2.01  AMENDMENTS  AND WAIVER OF  DEFAULT.  The  Debenture  may be
amended with the consent of the Holder.  Without the consent of the Holder,  the
Debenture  may be amended to cure any  ambiguity,  defect or  inconsistency,  to
provide for  assumption of the Company  obligations to the Holder or to make any
change that does not adversely affect the rights of the Holder.

                                  ARTICLE III.

      Section 3.01 EVENTS OF DEFAULT. An Event of Default is defined as follows:
(a) failure by the Company to pay amounts due hereunder within fifteen (15) days
of the date of maturity of this Debenture;  (b) failure of the Company to obtain
listing of the Common Stock on a Principal  Market  within six (6) months of the
date  hereof;  (c)  failure  by the  Company  to  comply  with the  terms of the
Irrevocable  Transfer Agent  Instructions  attached to the  Securities  Purchase
Agreement;  (d) failure by the Company's transfer agent to issue Common Stock to
the Holder within three (3) days of the Company's receipt of the attached Notice
of  Conversion  from Holder;  (e) failure by the Company for ten (10) days after
notice to it to comply with any of its other  agreements in this Debenture;  (f)
event of bankruptcy;  (g) a breach by the Company of its  obligations  under the


                                       3
<PAGE>

Securities Purchase Agreement,  the Investor  Registration Rights Agreement,  or
the Security  Agreement  which is not cured by the Company  within ten (10) days
after receipt of written notice thereof. As used herein,  Principal Market shall
mean The National  Association  of Securities  Dealers  Inc.'s  Over-The-Counter
Bulletin Board, Nasdaq SmallCap Market or American Stock Exchange.

      Section 3.02 FAILURE TO ISSUE  UNRESTRICTED  COMMON STOCK. As indicated in
Article III Section 3.01, a breach by the Company of its  obligations  under the
Investor  Registration  Rights  Agreement  shall be deemed an Event of  Default,
which if not cured within ten (10) days,  shall  entitle the Holder  accelerated
full  repayment of all debentures  outstanding.  The Company  acknowledges  that
failure to honor a Notice of  Conversion  shall  cause  irreparable  harm to the
Holder.

                                  ARTICLE IV.

      Section 4.01 RIGHTS AND TERMS OF CONVERSION.  This Debenture,  in whole or
in part, may be converted at any time following the date of closing, into shares
of Common Stock at a price equal to the Conversion Price as described in Section
1.02 above.

      Section 4.02 RE-ISSUANCE OF DEBENTURE. When the Holder elects to convert a
part of the  Debenture,  then the Company  shall  reissue a new Debenture in the
same form as this Debenture to reflect the new principal amount.

      Section 4.03  TERMINATION  OF  CONVERSION  RIGHTS.  The Holder's  right to
convert the Debenture  into the Common Stock in accordance  with  paragraph 4.01
shall terminate on the date that is the second (2nd) year  anniversary  from the
date hereof and this Debenture shall be automatically  converted on that date in
accordance  with  the  formula  set  forth  in  Section  4.01  hereof,  and  the
appropriate shares of Common Stock and amount of interest shall be issued to the
Holder.

                                   ARTICLE V.

      Section  5.01  ANTI-DILUTION.  In the event that the Company  shall at any
time subdivide the  outstanding  shares of Common Stock,  or shall issue a stock
dividend  on the  outstanding  Common  Stock,  the  Conversion  Price in  effect
immediately  prior to such subdivision or the issuance of such dividend shall be
proportionately  decreased,  and in the event that the Company shall at any time
combine the outstanding  shares of Common Stock,  the Conversion Price in effect
immediately  prior  to such  combination  shall  be  proportionately  increased,
effective at the close of business on the date of such subdivision,  dividend or
combination as the case may be.

      Section  5.02  CONSENT  OF HOLDER  TO SELL  COMMON  STOCK.  So long as any
Secured Convertible  Debentures are outstanding,  the Company shall not, without
the prior written  consent of the  Buyer(s):  (i) issue or sell shares of Common
Stock, (ii) issue any warrant,  option, right, contract, call, or other security
instrument  granting the holder  thereof,  the right to acquire Common Stock, or
(iii) file any registration statement on Form S-8.

                                       4
<PAGE>

                                  ARTICLE VI.

      Section 6.01 NOTICE. Notices regarding this Debenture shall be sent to the
parties at the following  addresses,  unless a party notifies the other parties,
in writing, of a change of address:

If to the Company, to:          Advanced Communications Technologies, Inc.
                                c/o Danson Partners, LLC
                                420 Lexington Avenue, Suite 2739
                                New York, New York 10170
                                Attention:  Wayne Danson, President and
                                            Chief Financial Officer
                                Telephone:  (646) 227-1600
                                Facsimile:  (646) 227-1666

With a copy to:                 Levinson & Lichtman, LLP
                                120 East Palmetto Park Road, Suite 100
                                Boca Raton, Florida 33432
                                Attention:  Jonathan J. Lichtman, Esq.
                                Telephone:  (561) 869-3600
                                Telephone:  (561) 869-3601



With a copy to:                 Kirkpatrick & Lockhart LLP
                                201 South Biscayne Boulevard - Suite 2000
                                Miami, FL  33131-2399
                                Attention:  Clayton E. Parker, Esq.
                                Telephone:  (305) 539-3300
                                Facsimile:  (305) 358-7095

If to the Holder:               Cornell Capital Partners, LP6
                                101 Hudson Street, Suite 360
                                Jersey City, New Jersey 07302
                                Facsimile:  (201) 985-8266


With a copy to:                 Butler Gonzalez LLP
                                1000 Stuyvesant Avenue, Suite 6
                                Union, New Jersey 07083
                                Attention: David Gonzalez, Esq.
                                Telephone:  (908) 810-8588
                                Facsimile:  (908) 810-0973

      Section 6.02  GOVERNING  LAW.  This  Debenture  shall be deemed to be made
under and shall be construed in accordance with the laws of the State of Florida
without giving effect to the principals of conflict of laws thereof. Each of the
parties consents to the  jurisdiction of the U.S.  District Court sitting in the
District  of the State of New  Jersey  or the  state  courts of the State of New


                                       5
<PAGE>

Jersey  sitting in Hudson  County,  New Jersey in  connection  with any  dispute
arising under this Debenture and hereby waives,  to the maximum extent permitted
by law, any objection,  including any objection based on forum non conveniens to
the bringing of any such proceeding in such jurisdictions.

      Section 6.03 SEVERABILITY. The invalidity of any of the provisions of this
Debenture shall not invalidate or otherwise  affect any of the other  provisions
of this Debenture, which shall remain in full force and effect.

      Section 6.04 ENTIRE  AGREEMENT AND AMENDMENTS.  This Debenture  represents
the entire  agreement  between  the parties  hereto with  respect to the subject
matter  hereof  and there are no  representations,  warranties  or  commitments,
except as set forth herein.  This Debenture may be amended only by an instrument
in writing executed by the parties hereto.

      Section  6.05  COUNTERPARTS.  This  Debenture  may be executed in multiple
counterparts,  each of which  shall be an  original,  but all of which  shall be
deemed to constitute on instrument.



                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


                                       6
<PAGE>

      IN  WITNESS  WHEREOF,  with the  intent to be legally  bound  hereby,  the
Company as executed this Debenture as of the date first written above.

                                    ADVANCED COMMUNICATIONS
                                      TECHNOLOGIES, INC.

                                    By:
                                       -----------------------------------------
                                    Name:  Wayne Danson
                                    Title: President and Chief Financial Officer

                                        7
<PAGE>
                                   EXHIBIT "A"
                                   -----------

                              NOTICE OF CONVERSION
                              --------------------

         (TO BE EXECUTED BY THE HOLDER IN ORDER TO CONVERT THE NOTE)


TO:

      The     undersigned     hereby     irrevocably     elects    to    convert
$___________________________  of the  principal  amount of the  above  Note into
Shares of Common Stock of Advanced Communications Technologies,  Inc., according
to the conditions stated therein, as of the Conversion Date written below.

Conversion Date:
                                   ------------------------------------------
Applicable Conversion Price:
                                   ------------------------------------------
Signature:
                                   ------------------------------------------
Name:
                                   ------------------------------------------
Address:
                                   ------------------------------------------
Amount to be converted:  $
                                   ------------------------------------------
Amount of Debenture
                                   ------------------------------------------
unconverted: $
                                   ------------------------------------------
Conversion Price per share: $
                                   ------------------------------------------
Number of shares of
Common Stock to be issued:
                                   ------------------------------------------
Please issue the shares of
Common Stock in the
following name and to the
following address:
                                   ------------------------------------------
Issue to:
                                   ------------------------------------------
Authorized Signature:
                                   ------------------------------------------
Name:
                                   ------------------------------------------
Title:
                                   ------------------------------------------
Phone Number:
                                   ------------------------------------------
Broker DTC Participant
Code:
                                   ------------------------------------------
Account Number:
                                   ------------------------------------------