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                                                                   Exhibit 10.20

================================================================================
                               LINE OF CREDIT NOTE
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$1,000,000.00                                                Birmingham, Alabama
                                                    Effective: September 5, 2003
                                                        Dated: September 8, 2003

     FOR VALUE RECEIVED, without grace, AEROSONIC CORPORATION, a Delaware
Corporation and AVIONICS SPECIALTIES, INC., a Virginia Corporation (hereinafter
collectively called the "Borrower"), jointly and severally, promise to pay to
the order of FIRST COMMERCIAL BANK, a state bank (hereinafter called the "Bank",
together with any subsequent holder of this Note called the "Holder"), on
demand, or in the manner set forth below, the principal sum of ONE MILLION AND
N0/100 DOLLARS ($1,000,000.00), or so much thereof as may be advanced by the
Bank hereunder, plus interest on the unpaid principal balance of the amount
advanced hereunder from the date advanced until payment in full at the rate set
forth below. All interest on this Note will be computed on the basis of the
actual number of days elapsed over an assumed 360 day year.

     This Note shall bear interest on the unpaid principal balance hereof at the
rate designated by First Commercial Bank as its prime rate (Current Prime Rate
is 4%) in effect from time to time (the "Prime Rate"). Any change in the
interest rate on this Note caused by a change in the Prime Rate shall take
effect on the effective date such change as designated by the payee Bank,
without notice to the Borrower and without any further action by the Bank.

     The Borrower will pay interest only on the unpaid principal balance hereof
with the first payment due on September 30, 2003 and on the 30th day of each
month thereafter. This Note is due and payable on demand, and if no demand is
made, is due and payable on December 5, 2003. All amounts received by Lender
shall be applied first to accrued, unpaid interest, then to unpaid principal,
and then to any late charges or expenses, or in any other order as determined by
Lender, in Lender's sole discretion, as permitted by law. An interest surcharge
of $250.00 has been paid by the Borrower.

     This is a Line of Credit Note and the Borrower hereby authorizes the bank
to accept all written draw requests submitted by Borrower, and to disburse the
advances under the draw request as directed by Borrower. The advances made under
the written draw requests shall, in the absence of manifest error, be conclusive
as to the advance and conclusive to the outstanding principal amount of all
Loans when such advance or advances are added to the then outstanding principal
amount; provided, however, that the failure to make such notation with respect
to any Loan or payment shall not limit or otherwise affect the obligations of
the Borrower under the Loan Documents or this Note.

     Borrower shall pay to Bank a late charge equal to the greater of $25.00 or
five percent (5%) of any amount, including any interest, not paid within ten
(10) days of the due date of such amount, not as a penalty, but as compensation
to the Bank for the cost of collecting and processing such late payment,
provided, such late charge shall not exceed the sum of $999.99. Borrower agrees
that such late charge represents a good faith reasonable estimate of the
probable cost to Bank of such delinquency. Bank shall have no obligation to
accept any late payment not accompanied by said late charge, but if Bank does
so, Bank shall not thereby waive its right to the late charge.

     This Note is secured by the following instrument or instruments executed
and delivered to the payee Bank (such instrument or instruments are hereinafter
referred to as the "Security Document," whether one instrument or more):

                                                        Promissory Note - Page 1

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INSTRUMENT:                   EXECUTED BY:                 DATED:

SECURITY AGREEMENT            Aerosonic Corporation        September 17, 1997
   (Accounts, Inventory and
      General Intangibles)

SECURITY AGREEMENT            Avionics Specialties, Inc.   September 17, 1997
   (Accounts, Inventory and
      General Intangibles)

     It is hereby agreed that if default be made in the payment of this Note or
any part hereof or any interest hereon, or if failure be made to perform any of
the covenants, agreements or stipulations contained in any Security Document, or
upon the occurrence of any event of default as set forth hereinafter, then, at
the option of the Bank, the entire unpaid principal balance of this Note, with
accrued interest thereon, shall at once become due and payable in full, without
notice, time being of the essence of this contract. As used herein, "default"
and "event of default" shall mean the occurrence or happening of any one or more
of the following events, circumstances or conditions: (a) default in the payment
of this Note or any part hereof or any interest hereon as and when due and such
default shall continue for ten (10) calendar days, or the failure in the timely
performance of any of the covenants, agreements or stipulations contained in any
Security Document; (b) the default by the Borrower in the due payment of any
amount evidenced by, or the performance of any obligation in, this Note or any
Security Document; (c) the misrepresentation or distortion by the Borrower or a
Guarantor of any material fact in any statement, report, certification or
representation made to the Bank at any time; (d) the loss, theft, damage, sale,
seizure, attachment or encumbrance of any material portion of the collateral
described in any Security Document; (e) the dissolution or liquidation or
insolvency of the Borrower, (f) the filing of a voluntary or involuntary
petition under any provision of any federal or state bankruptcy statute (whether
for bankruptcy, reorganization, arrangement, readjustment of debt, composition,
extension, wage earner's plan or otherwise) by or against the Borrower, or the
taking by the Borrower of corporate action for the purpose of effecting any of
the foregoing; (g) the appointment of a receiver, trustee or liquidator of the
Borrower or of all or a substantial part of the Borrower's properties or assets,
or the adjudication of the Borrower as a bankrupt or insolvent, or the entry of
any order for relief against the Borrower in any voluntary or involuntary
bankruptcy or reorganization case; (h) the general assignment for the benefit of
creditors of the Borrower; (i) the failure or admission of the inability of the
Borrower generally to pay the Borrower's debts as they become due; (j) the
business failure of the Borrower; (k) the entry of a judgment against the
Borrower, and the same shall not be satisfied in full or stayed within a period
of thirty (30) days or the issuance of a writ of attachment or garnishment
against the Borrower; (l) the failure by the Borrower to pay when due any
insurance premium that may be required under the terms of any Security Document
or any assessment or any taxes when due; or (m) the occurrence of any default or
event of default as set forth in any Security Document.

     The Borrower and all sureties, endorsers and guarantors of this Note,
jointly and severally, waive demand, presentment for payment, notice of
nonpayment, protest, notice of protest, and all other notice, filing of suit and
diligence in collecting this Note, or the release of any party primarily or
secondarily liable thereon, and further, jointly and severally, agree that it
will not be necessary for the Bank, in order to enforce payment of this Note,
first to institute suit, and jointly and severally, consent to any one or more
extensions or postponements of time of payment of this Note or any other
indulgences with respect hereto, without notice thereof to any of them.

     The Borrower agrees to pay all costs of collecting or securing or
attempting to collect to secure this Note, including court costs and reasonable
attorney's fees and further waives all right of exemption under the
Constitution and Laws of Alabama.

     The Bank may, but shall not be required to, apply on or after maturity, to
the payment of the indebtedness evidenced hereby, any funds or credit held by
the Bank on deposit, in trust or otherwise, for the account of the Borrower or
any other party liable hereon.

                                                        Promissory Note - Page 2

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     The Borrower understands that the Bank may from time to time enter into a
participation agreement or agreements with one or more participants pursuant to
which such participant or participants shall be given participations in advances
made under this Note and that such participants may from time to time similarly
grant to other participants subparticipations in such advances. Any participant
or subparticipant may exercise any and all rights of banker's lien or set-off
with respect to the Borrower or any other party liable hereon, as fully as if
such participant or subparticipant had made a loan directly to the Borrower or
such other party in the amount of the participation or subparticipation given to
such participant or subparticipant in the advances on this Note. For the
purposes of this paragraph only, the Borrower and every other party liable
hereon shall be deemed to be directly obligated to each participant or
subparticipant in the amount of its participating interest in the amount of the
principal of, and interest on, advances made under this Note.

     THE BORROWER HEREBY WAIVES THE RIGHT TO TRIAL BY JURY IN ANY ACTION OR
PROCEEDING BASED UPON, ARISING OUT OF OR IN ANY WAY CONNECTED TO THIS PROMISSORY
NOTE, THE LOAN BEING MADE EVIDENCED BY THIS PROMISSORY NOTE OR THE SUBJECT
MATTER HEREOF. .

     The Borrower agrees that any action or proceeding relating to this Note may
by brought and enforced in the courts of the State of Alabama, 10th Judicial
Circuit, or of the United States District Court, Northern District of Alabama,
and irrevocably submits to the jurisdiction of each such court and any appellate
court from any thereof in any action or proceeding arising out of or relating to
this Note, and the Borrower irrevocably agrees that all claims in respect of
such action or proceeding may be heard and determined in such State court or in
such federal court. Nothing herein shall affect the right of the Bank to bring
any action or proceeding against the Borrower or its property in the courts of
any other jurisdictions. The Borrower irrevocably waives, to the fullest extent
permitted by law, any objection which it may have now or hereafter have to the
laying of venue of any action or proceeding relating to this Note brought in the
State of Alabama, 10th Judicial Circuit, or the United States District Court,
Northern District of Alabama, and any claim that any such action or proceeding
brought in any such court has been brought in an inconvenient forum. The
Borrower irrevocably consents to the service of any and all process in any such
action or proceeding by the mailing of copies of such process to the Borrower at
the address herein specified. The Borrower agrees that a final judgment in any
such action or proceeding shall be conclusive and may be enforced in other
jurisdictions by suit on the judgment or in any other manner provided by law.

     This Note has been executed by the Borrower without condition that anyone
else should sign or become bound hereunder and without any other conditions
whatever being made. The provisions hereof are binding on the successors and
assigns of the Borrower and shall inure to the benefit of the payee Bank and its
successors and assigns.

     The Bank shall not by any act, delay, omission or otherwise be deemed to
have waived any of its rights or remedies, and no waiver of any kind shall be
valid against the Bank unless in writing and signed by the Bank. All rights and
remedies hereunder and under any statute or rule of law shall be cumulative and
may be exercised successively or concurrently. This Note shall be governed by
and construed in accordance with the laws of the State of Alabama.

     This Note is one of two (2) Notes executed by Borrower and a default under
the terms and conditions of either Note will constitute a default under this
Note.

     This Note is a Renewal Note of that certain Line of Credit Note executed by
Borrower to Bank dated September 17, 1997 in the amount of $1,500,040.00; as
renewed by Line of Credit Note dated May 28, 1998, with an effective date of
April 30, 1998, in the amount of $1,500,080.00; further renewed by Line of
Credit Note dated August 27, 1999, with an effective date of August 30, 1999, in
the amount of $2,000,000.00; further renewed by Line of Credit Note dated July
26, 2000 in the amount of $1,000,000.00; further renewed by Line of Credit Note
dated June 22, 2001, with an effective date of May 30, 2001, in the amount of
$1,000,000.00; further renewed by Line of Credit Note dated July 19, 2002, with
an effective date of May 30, 2002, in the amount of $1,000,000.00; further
renewed by Line of Credit Note dated June 13, 2003, with an effective date of
May 30, 2003 in the amount of $1,000,000.00, with an outstanding principal
balance of $1,000,000.00 (collectively the "Existing Note") which Existing Note
is owned and held by Bank. The Existing Note and the payment terms thereof are
hereby consolidated, modified and restated, and, effective with the date hereof,
all the terms of the Existing Note are superseded by, and subsumed within, the
terms hereof so as to extend and renew the existing indebtedness; provided,
however, that this Renewal Promissory Note shall

                                                        Promissory Note - Page 3

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not operate to discharge, satisfy, cancel, release or repay, or be deemed a
substitution or novation of, the indebtedness heretofore evidenced by the
Existing Note, which indebtedness is hereby expressly preserved and confirmed in
all respects. The Bank may retain the Existing Note in its file along with this
Renewal Promissory Note until the indebtedness evidenced hereby is paid in full.

     This Note is executed under Seal by Borrower.

CAUTION - IT IS IMPORTANT THAT YOU THOROUGHLY READ THIS PROMISSORY NOTE BEFORE
YOU SIGN IT.

ATTEST:                            AEROSONIC CORPORATION, a Delaware Corporation


By:                                By: /s/ Gary Colbert
    ----------------------------       -----------------------------------------
    Its                                             Gary Colbert
        ------------------------                [Print or Type Name]

                                              Chief Financial Officer
                                                 [Title of Officer]


WITNESSES:


/s/ Lori Williams
--------------------------------


/s/ Wanda Elliott
--------------------------------


ATTEST:                            AVIONICS SPECIALTIES, INC., a Virginia
                                   Corporation


By:                                By: /s/ Gary Colbert
    ----------------------------       -----------------------------------------
    Its                                             Gary Colbert
        ------------------------                [Print or Type Name]

                                              Chief Financial Officer
                                                 [Title of Officer]


WITNESSES:


/s/ Lori Williams
--------------------------------


/s/ Wanda Elliott
--------------------------------

                                                        Promissory Note - Page 4

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STATE OF FLORIDA     )
COUNTY OF PINELLAS   )

     The foregoing instrument was acknowledged before me this 16th day of
September, 2003 by Gary Colbert, Chief Financial Officer of AEROSONIC
CORPORATION, a Delaware Corporation, on behalf of the corporation. He is
personally known to me or has produced Driver's License as identification.


[SEAL]                                         /s/ Lois K. Abraham
                                   ---------------------------------------------
[SEAL]      Lois K. Abraham                      [NOTARY PUBLIC]
         Commission # CC 965369
          Expires Sep. 9, 2004                    Lois K. Abraham
              Bonded Thru                      [Print or Type Name]
       Atlantic Bonding Co., Inc.

STATE OF FLORIDA     )
COUNTY OF PINELLAS   )

     The foregoing instrument was acknowledged before me this 16th day of
September, 2003 by Gary Colbert, Chief Financial Officer of AVIONICS
SPECIALTIES, INC., a Delaware Corporation, on behalf of the corporation. He is
personally known to me or has produced Driver's License as identification.


[SEAL]                                         /s/ Lois K. Abraham
                                   ---------------------------------------------
[SEAL]      Lois K. Abraham                      [NOTARY PUBLIC]
         Commission # CC 965369
          Expires Sep. 9, 2004                    Lois K. Abraham
              Bonded Thru                      [Print or Type Name]
       Atlantic Bonding Co., Inc.

This instrument Prepared By:

Claude McCain Moncus, Esq.
CORLEY, MONCUS & WARD, P.C.
400 Shades Creek Parkway
Suite l00
Birmingham, Alabama 35209
(205) 879-5859

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