Document:

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                                                                    EXHIBIT 10.3

                            REVOLVING PROMISSORY NOTE

$12,500,000.00                                                September 30, 2002

         FOR VALUE RECEIVED, on or before September 29, 2003 ("Maturity Date")
the undersigned and if more than one, each of them, jointly and severally
("Borrower"), does hereby unconditionally promise to pay to the order of BANK
ONE, NA, successor by merger to BANK ONE, TEXAS, N.A., a national banking
association ("Bank"), at its offices in Dallas County, Texas at 1717 Main
Street, Dallas, Texas 75201, the principal amount of TWELVE MILLION FIVE HUNDRED
THOUSAND AND NO/100 DOLLARS ($12,500,000.00) ("Total Principal Amount"), or such
amount less than the Total Principal Amount which is outstanding from time to
time if the total amount outstanding under this Revolving Promissory Note (this
"Note") is less than the Total Principal Amount, in lawful money of the United
States of America, together with interest on such portion of the Total Principal
Amount which has been drawn until paid at the rates per annum provided below.

         1.     Definitions. For purposes of this Note, unless the context
otherwise requires, the following terms shall have the definitions assigned to
such terms as follows:

         "Adjusted LIBOR Rate" shall mean with respect to each Interest Period,
on any day thereof an amount equal to the sum of (i) the quotient of (a) the
LIBOR Rate with respect to such Interest Period (the "Index"), divided by (b)
the remainder of 1.0 less the Reserve Requirement in effect on such day, plus
(ii) a specified percentage (the "LIBOR Margin") based on the ratio of
Borrower's total Funded Indebtedness (as defined in the Loan Agreement) to
EBITDA (as defined in the Loan Agreement), determined as follows:

               Ratio of Funded Indebtedness To
                           EBITDA                   LIBOR Margin
               -------------------------------------------------
                          * 1.00                        2.25%
                     ** 1.00, * 2.00                    2.75%
                         ** 2.00                        3.25%

         Each determination by Bank of the Adjusted LIBOR Rate shall, in the
absence of manifest error, be conclusive and binding.

         "Business Day" shall mean any day other than a Saturday, Sunday or any
other day on which national banking associations are authorized to be closed.

         "Consequential Loss" shall mean, with respect to Borrower's payment of
all or any portion of the then outstanding principal amount of any LIBOR Balance
on a day other than the last day of the Interest Period related thereto, any
loss, cost or expense incurred by Bank in redepositing such principal amount,
including the sum of (i) the interest which, but for such payment, Bank would
have earned in respect of such principal amount so paid, for the remainder

* denotes less than
** denotes greater than

                                                                          Page 1

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of the Interest Period applicable to such sum, reduced, if Bank is able to
redeposit such principal amount so paid for the balance of such Interest Period,
by the interest earned by Bank as a result of so redepositing such principal
amount plus (ii) any expense or penalty incurred by Bank on redepositing such
principal amount.

         "Contract Rate" shall mean a rate of interest based upon the Adjusted
LIBOR Rate or the Prime Rate in effect at any time pursuant to an Interest
Notice.

         "Dollars" shall mean lawful currency of the United States of America.

         "Event of Default" shall mean the occurrence of an event of default
specified in the Loan Agreement (as hereinafter defined).

         "Excess Interest Amount" shall mean, on any date, the amount by which
(i) the amount of all interest which would have accrued prior to such date on
the principal of this Note, had the applicable Contract Rate at all times been
in effect without limitation by the Maximum Rate, exceeds (ii) the aggregate
amount of interest accrued on this Note on or prior to such date.

         "Interest Notice" shall mean the notice given by Borrower to Bank of
the Interest Options selected hereunder. Each Interest Notice shall specify the
Interest Option selected, the amount of the unpaid principal balance of this
Note to bear interest at the rate selected and, if the Adjusted LIBOR Rate is
specified, the length of the applicable Interest Period. An Interest Notice may
be written or oral (if promptly confirmed thereafter in writing) and Bank is
hereby authorized and directed to honor all telephonic Interest Notices from any
person authorized to request advances hereunder.

         "Interest Option" shall have the meaning assigned to such term in
paragraph 6 hereof.

         "Interest Payment Date" shall mean (i) in the case of the Prime Rate
Balance, on the last day of December, 2002 and on the last day of each calendar
quarter thereafter, until the Maturity Date and on the Maturity Date, and (ii)
in the case of any LIBOR Balance, on the earlier of (a) the last day of the
corresponding Interest Period with respect to such LIBOR Balance, or (b) the
last day of December, 2002, and on the last day of each calendar quarter
thereafter until the Maturity Date, and on the Maturity Date.

         "Interest Period" shall mean each consecutive one month, two month and
three month period (the first of which shall commence on the date of this Note)
effective as of the first day of each Interest Period and ending on the last day
of each Interest Period, provided that if any Interest Period is scheduled to
end on a date for which there is no numerical equivalent to the date on which
the Interest Period commenced, then it shall end instead on the last day of such
calendar month.

         "LIBOR Balance" shall mean any principal balance of this Note which,
pursuant to an Interest Notice, bears interest at a rate based upon the Adjusted
LIBOR Rate for the Interest Period specified in such Interest Notice.

                                                                          Page 2

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         "LIBOR Rate" shall mean the offered rate for U.S. Dollar deposits of
not less than $100,000.00 for a period of time equal to each Interest Period as
of 11:00 A.M. City of London, England time two London Business Days prior to the
first date of each Interest Period of this Note as shown on the display
designated as "British Bankers Assoc. Interest Settlement Rates" on the Telerate
System ("Telerate"), Page 3750 or Page 3740, or such other page or pages as may
replace such pages on Telerate for the purpose of displaying such rate.
Provided, however, that if such rate is not available on Telerate then such
offered rate shall be otherwise independently determined by Bank from an
alternate, substantially similar independent source available to Bank or shall
be calculated by Bank by a substantially similar methodology as that theretofore
used to determine such offered rate in Telerate. Each change in the rate to be
charged on this Note will become effective without notice on the commencement of
each Interest Period based upon the Index then in effect.

         "Loan Agreement" shall mean that certain Letter Loan Agreement by and
between Bank and Borrower dated September 30, 2002, as amended from time to
time.

         "Loan Documents" shall mean this Note, the Term Note (as defined in the
Loan Agreement), the EXIM Loan Documents (as defined in the Loan Agreement), the
Loan Agreement and all other documents evidencing, securing, governing,
guaranteeing and/or pertaining to the Loan Agreement.

         "London Business Day" means any day other than a Saturday, Sunday or a
day on which banking institutions are generally authorized or obligated by law
or executive order to close in the City of London, England.

         "Maximum Rate" shall mean, with respect to the holder hereof, the
maximum nonusurious interest rate, if any, that at any time, or from time to
time, may be contracted for, taken, reserved, charged, or received on the
indebtedness evidenced by this Note under the laws which are presently in effect
in the United States and the State of Texas applicable to such holder and such
indebtedness or, to the extent permitted by law, under such applicable laws of
the United States and the State of Texas which may hereafter be in effect and
which allow a higher maximum nonusurious interest rate than applicable laws now
allow. To the extent that Chapter 303 of the Texas Finance Code ("Code"), is
relevant to any holder of this Note for the purposes of determining the Maximum
Rate, each such holder elects to determine such applicable legal rate under the
Act pursuant to the "weekly ceiling," from time to time in effect, as referred
to and defined in Chapter 303 of the Code; subject, however, to the limitations
on such applicable ceiling referred to and defined in Chapter 303 of the Code,
and further subject to any right such holder may have subsequently, under
applicable law, to change the method of determining the Maximum Rate. If no
Maximum Rate is established by applicable law, then the Maximum Rate shall be
equal to eighteen percent (18%).

         "Prime Rate" shall mean the sum of (a) the rate established from time
to time by Bank as its prime rate of interest (which may not be the lowest, best
or most favorable rate of interest which Bank may charge on loans to its
customers), plus (b) a specified percentage (the "Base Rate Margin") based on
the ratio of Borrower's total Funded Indebtedness (as defined in the Loan
Agreement) to EBITDA (as defined in the Loan Agreement), determined as follows:

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          Ratio of Funded Indebtedness to
                      EBITDA                 Base Rate Margin
          ---------------------------------------------------
                          * 1.00                   0.00%
                     ** 1.00, * 2.00               0.50%
                         ** 2.00                   1.00%

         "Prime Rate Balance" shall mean that portion of the principal balance
of this Note bearing interest at a rate based upon the Prime Rate.

         "Regulation D" shall mean Regulation D of the Board of Governors of the
Federal Reserve System from time to time in effect and shall include any
successor or other regulation relating to reserve requirements applicable to
member banks of the Federal Reserve System.

         "Reserve Requirement" shall, on any day, mean that percentage
(expressed as a decimal fraction) which is in effect on such day, as provided by
the Board of Governors of the Federal Reserve System (or any successor
governmental body) for determining the reserve requirements (including without
limitation, basic, supplemental, marginal and emergency reserves) under
Regulation D with respect to "Eurocurrency liabilities" as currently defined in
Regulation D, or under any similar or successor regulation. For purposes of this
definition, any LIBOR Balances hereunder shall be deemed "Eurocurrency
liabilities" under Regulation D without benefit of or credit for prorations,
exemptions or offsets under Regulation D. Bank's determination of the Reserve
Requirement shall be conclusive in the absence of manifest error.

         2.     Payments of Interest and Principal. Interest on the unpaid
principal balance of this Note shall be due and payable on each Interest Payment
Date as it accrues and the entire unpaid principal balance of this Note, and all
accrued but unpaid interest thereon, shall be due and payable on the Maturity
Date.

         3.     Rates of Interest. The unpaid principal of the Prime Rate
Balance shall bear interest at a rate per annum which shall from day to day be
equal to the lesser of (i) the Prime Rate in effect from day to day, or (ii) the
Maximum Rate. The unpaid principal of each LIBOR Balance shall bear interest at
a rate per annum which shall from day to day be equal to the lesser of (i) the
Adjusted LIBOR Rate for the Interest Period in effect with respect to such LIBOR
Balance, or (ii) the Maximum Rate. Each change in the interest rate applicable
to a Prime Rate Balance shall become effective without prior notice to Borrower
automatically as of the opening of business on the date of such change in the
Prime Rate. Interest on this Note shall be calculated on the basis of the actual
days elapsed in a year consisting of 360 days.

         4.     Interest Recapture. If on each Interest Payment Date or any
other date on which interest payments are required hereunder, Bank does not
receive interest on this Note computed at the Contract Rate because such
Contract Rate exceeds or has exceeded the Maximum Rate,

* denotes less than
** denotes greater than

                                                                          Page 4

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then Borrower shall, upon the written demand of Bank, pay to Bank in addition to
the interest otherwise required to be paid hereunder, on each Interest Payment
Date thereafter, the Excess Interest Amount (calculated as of such later
Interest Payment Date); provided that in no event shall Borrower be required to
pay, for any Interest Period, interest at a rate exceeding the Maximum Rate
effective during such period.

         5.     Interest on Past Due Amounts. To the extent any interest is not
paid on or before the fifth day after it becomes due and payable, Bank may, at
its option, add such accrued but unpaid interest to the principal of this Note.
Notwithstanding anything herein to the contrary, upon an Event of Default or at
maturity, whether by acceleration or otherwise, all principal of this Note
shall, at the option of Bank, bear interest at the Prime Rate plus 4% (the
"Default Rate") until paid; provided, however, the Default Rate shall at no time
exceed the Maximum Rate.

         6.     Interest Option. Subject to the provisions hereof, Borrower
shall have the option (an "Interest Option") of having designated portions of
the unpaid principal balance of this Note bear interest at a rate based upon the
Adjusted LIBOR Rate or Prime Rate as provided in paragraph 3 hereof, provided,
however, that the selection of the Adjusted LIBOR Rate for a particular Interest
Period shall not be for less than $100,000.00 of unpaid principal or an integral
multiple thereof. The Interest Option shall be exercised in the manner provided
below:

                (i)    At Time of Borrowing. Contemporaneously with each request
         for an advance by Borrower under Paragraph 9 herein, Borrower shall
         give Bank an Interest Notice indicating the initial Interest Option
         selected with respect to the principal balance of such advance.

                (ii)   At Expiration of Interest Periods. Unless otherwise
         agreed to by Bank, at least two (2) Business Days prior to the
         termination of any Interest Period, Borrower shall give Bank an
         Interest Notice indicating the Interest Option to be applicable to the
         corresponding LIBOR Balance upon the expiration of such Interest
         Period. If the required Interest Notice shall not have been timely
         received by Bank prior to the expiration of the then-relevant Interest
         Period, Borrower shall be deemed to have selected a rate based upon the
         Prime Rate to be applicable to such LIBOR Balance upon the expiration
         of such Interest Period and to have given Bank notice of such
         selection.

                (iii)  Conversion From Prime Rate. During any period in which
         any portion of the principal hereof bears interest at a rate based upon
         the Prime Rate, Borrower shall have the right, on any London Business
         Day (the "Conversion Date"), to convert all or a portion of such
         principal amount from the Prime Rate Balance to a LIBOR Balance by
         giving Bank an Interest Notice of such selection at least two (2)
         London Business Days prior to such Conversion Date, or as otherwise
         agreed to by Bank.

An Interest Notice may be written or oral and Bank is hereby authorized and
directed to honor all telephonic Interest Notices hereunder. Borrower agrees to
indemnify and hold Bank harmless from any loss or liability incurred by Bank in
connection with honoring any telephonic or other

                                                                          Page 5

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oral Interest Notices. All written Interest Notices are effective only upon
receipt by Bank. Each Interest Notice shall be irrevocable and binding upon
Borrower.

         7.     Special Provisions For LIBOR Pricing.

                a.     Inadequacy of LIBOR Loan Pricing. If Bank determines
that, by reason of circumstances affecting the interbank eurodollar market
generally, deposits in Dollars (in the applicable amounts) are not being offered
to United States financial institutions in the interbank eurodollar market for
such Interest Period, or that the rate at which such Dollar deposits are being
offered will not adequately and fairly reflect the cost to Bank of making or
maintaining a LIBOR Balance for the applicable Interest Period, Bank shall
forthwith give notice thereof to Borrower, whereupon until Bank notifies
Borrower that the circumstances giving rise to such suspension no longer exist,
(i) the right of Borrower to select an Interest Option based upon the LIBOR Rate
shall be suspended, and (ii) Borrower shall be deemed to have converted each
LIBOR Balance to the Prime Rate Balance in accordance with the provisions hereof
on the last day of the then-current Interest Period applicable to such LIBOR
Balance.

                b.     Illegality. If the adoption of any applicable law, rule
or regulation, or any change therein, or any change in the interpretation or
administration thereof by any governmental authority, central bank or comparable
agency charged with the interpretation or administration thereof, or compliance
by Bank with any request or directive (whether or not having the force of law)
of any such authority, central bank or comparable agency shall make it unlawful
or impossible for Bank to make or maintain a LIBOR Balance, Bank shall so notify
Borrower. Upon receipt of such notice, Borrower shall be deemed to have
converted any LIBOR Balance to the Prime Rate Balance, on either (i) the last
day of the then-current Interest Period applicable to such LIBOR Balance if Bank
may lawfully continue to maintain and fund such LIBOR Balance to such day, or
(ii) immediately, if Bank may not lawfully continue to maintain such LIBOR
Balance to such day.

         8.     Extension, Place and Application of Payments. Should the
principal of, or any interest on, this Note become due and payable on any day
other than a Business Day, the maturity thereof shall be extended to the next
succeeding Business Day, and interest shall be payable with respect to such
extension. All payments of principal of, and interest on, this Note shall be
made in lawful money of the United States of America in immediately available
funds. Payments made to Bank by Borrower hereunder shall be applied first to
accrued but unpaid interest and then to outstanding principal.

         9.     Advances. Subject to the terms of this Note and the Loan
Agreement, Borrower may request advances ("Advances") hereunder and make
payments from time to time during the term of this Note, provided that it is
understood and agreed that the aggregate principal amount outstanding from time
to time hereunder shall not exceed the sum of the Total Principal Amount. The
unpaid balance of this Note shall increase and decrease with each new Advance or
payment hereunder as the case may be. This Note shall not be deemed terminated
or cancelled prior to the Maturity Date, although the entire principal balance
hereof may from time to time be paid in full. Subject to the provisions of this
Note and the Loan Agreement, Borrower may borrow, repay and reborrow hereunder
from the date hereof until the Maturity Date. Subject to the provisions of

                                                                          Page 6

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Paragraph 6 herein, each Advance hereunder shall be in an amount not less than
$100,000.00 or an integral multiple thereof. If any Advance request is received
by Bank on or prior to 12:00 p.m. (Dallas, Texas time) on funds designated to
accrue interest at the Prime Rate, Bank shall make available at Bank's office in
Dallas, Texas not later than 2:00 p.m. (Dallas, Texas time) on the day of such
Advance request (or the date specified in such request), the amount of such
request in immediately available funds. If any Advance request is received by
Bank after 12:00 p.m. (Dallas, Texas time) on funds designated to accrue
interest at the Prime Rate, Bank shall make available at Bank's office in
Dallas, Texas not later than 2:00 p.m. (Dallas, Texas time) on the Business Day
after the day of such request (or a later date if specified in such request),
the amount of such request in immediately available funds. Each request for an
Advance on funds designated to accrue interest at the Adjusted LIBOR Rate must
be received by Bank not less than three (3) Business Days prior to the date upon
which the Advance requested is desired by Borrower. Each request for an Advance
hereunder must be accompanied by an Interest Notice for the funds to be advanced
thereunder, provided, however, if an Interest Notice does not accompany an
Advance request, Borrower shall be deemed to have designated the Prime Rate.
Each request for an Advance by Borrower hereunder shall be irrevocable and
binding on Borrower. An Advance request may be written or oral and Bank is
authorized and directed to honor all telephonic requests for Advances from any
person authorized to request Advances hereunder. Borrower agrees to indemnify
and hold Bank harmless from any loss or liability incurred by Bank in connection
with honoring any such telephonic or other oral requests for Advances. All
written Advance requests are effective only upon receipt by Bank.

         10.    Loan Agreement. This Note is subject to the terms and provisions
of the Loan Agreement, which is incorporated herein by reference for all
purposes. The holder of this Note is entitled to the benefits provided in the
Loan Agreement.

         11.    Prepayments, Consequential Loss. Any prepayment made hereunder
shall be made together with all interest accrued but unpaid on this Note through
the date of such prepayment. Contemporaneously with each prepayment of
principal, Borrower shall give Bank written or oral notice indicating whether
such prepayment is to be applied to the Prime Rate Balance or a particular LIBOR
Balance. If such notice is not timely received by Bank, Borrower shall be deemed
to have selected to prepay the Prime Rate Balance and, if any sums remain after
satisfying all of the Prime Rate Balance, the remaining sums shall be applied to
any LIBOR Balance(s) that Bank determines in its sole discretion. Borrower
agrees to indemnify and hold Bank harmless from any loss or liability incurred
by Bank in connection with honoring telephonic or other oral notices indicating
how a prepayment is to be applied. If Borrower makes any such prepayment other
than on the last day of an Interest Period, Borrower shall pay all accrued
interest on the principal amount prepaid with such prepayment and, on demand,
shall reimburse Bank and hold Bank harmless from all losses and expenses
incurred by Bank as a result of such prepayment, including, without limitation,
any losses and expenses arising from the liquidation or reemployment of deposits
acquired to fund or maintain the principal amount prepaid. Such reimbursement
shall be calculated as though Bank funded the principal amount prepaid through
the purchase of U.S. Dollar deposits in the London, England interbank market
having a maturity corresponding to such Interest Period and bearing an interest
rate equal to the LIBOR Rate for such Interest Period, whether in fact that is
the case or not. Bank's

                                                                          Page 7

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determination of the amount of such reimbursement shall be conclusive in the
absence of manifest error.

         12.    Additional Costs. Borrower agrees to pay to Bank all Additional
Costs within ten (10) days of receipt by Borrower from Bank of a statement
setting forth the amount or amounts due and the basis for the determination from
time to time of such amount or amounts, which statement shall be conclusive and
binding upon Borrower absent manifest error. Failure on the part of Bank to
demand compensation for any Additional Costs in any Interest Period shall not
constitute a waiver of Bank's right to demand compensation for any Additional
Costs incurred during any such Interest Period or in any other subsequent or
prior Interest Period. The term "Additional Costs" shall mean such additional
amount or amounts as Bank shall reasonably determine will compensate Bank for
actual costs incurred by Bank in maintaining LIBOR Rates on the LIBOR Balances
or any portion thereof as a result of any change, after the date of this Note,
in applicable law, rule or regulation or in the interpretation or administration
thereof by, or the compliance by Bank with any request or directive from, any
domestic or foreign governmental authority charged with the interpretation or
administration thereof (whether or not having the force of law) or by any
domestic or foreign court changing the basis of taxation of payments to Bank of
the LIBOR Balances or interest on the LIBOR Balances or any portion thereof at
an Adjusted LIBOR Rate or any other fees or amounts payable under this Note or
the Loan Agreement (other than taxes imposed on all or any portion of the
overall net income of Bank by the State of Texas or the Federal government), or
imposing, modifying or applying any reserve, special deposit or similar
requirement against assets of, deposits with or for the account of, credit
extended by, or any other acquisition of funds for loans by Bank, or imposing on
Bank, as the case may be, or on the London interbank market any other condition
affecting this Note, the Loan Agreement or the LIBOR Balances so as to increase
the cost of Bank making or maintaining Adjustable LIBOR Rates with respect to
the LIBOR Balances or any portion thereof or to reduce the amount of any sum
received or receivable by Bank under this Note or the Loan Agreement (whether of
principal, interest or otherwise), by an amount deemed by Bank in good faith to
be material, but without duplication for Reserve Requirement. Bank agrees that
it will not demand compensation for any Additional Costs from Borrower unless it
is seeking similar compensation from its other customers similarly situated.

         13.    Notices. Except as otherwise specified herein, all notices and
requests required or permitted hereunder shall be in writing and shall be deemed
to have been given when personally delivered or, if mailed, two Business Days
after deposited in a regularly maintained receptacle for the United States
Postal Service, postage prepaid, registered or certified, return receipt
requested, addressed to Borrower or Bank at the following respective addresses
or such other address as such party may from time to time designate by written
notice to the other: Borrower: 3000 Research Drive, Richardson, Texas 75082,
Attention: Jean Nelson; Bank: 1717 Main Street, Dallas, Texas 75201, Attention:
Frederick A. Points.

         14.    Legal Fees. If this Note is placed in the hands of any attorney
for collection, or if it is collected through any legal proceeding at law or in
equity or in bankruptcy, receivership or other court proceedings, Borrower
agrees to pay all costs of collection including, but not limited to, court costs
and reasonable attorneys' fees.

                                                                          Page 8

<PAGE>

         15.    Waivers. Borrower and each surety, endorser, guarantor and any
other party ever liable for payment of any sums of money payable on this Note,
jointly and severally waive presentment and demand for payment, protest, notice
of protest, intention to accelerate, acceleration and non-payment, or other
notice of default, and agree that their liability under this Note shall not be
affected by any renewal or extension in the time of payment hereof, or in any
indulgences, or by any release or change in any security for the payment of this
Note, and hereby consent to any and all renewals, extensions, indulgences,
releases or changes, regardless of the number of such renewals, extensions,
indulgences, releases or changes; provided, however, this Note may not be
amended or modified except by a written instrument signed by the Borrower and
the holder hereof.

         No waiver by Bank of any of its rights or remedies hereunder or under
any other document evidencing or securing this Note or otherwise shall be
considered a waiver of any other subsequent right or remedy of Bank; no delay or
omission in the exercise or enforcement by Bank of any rights or remedies shall
ever be construed as a waiver of any right or remedy of Bank; and no exercise or
enforcement of any such rights or remedies shall ever be held to exhaust any
right or remedy of Bank.

         16.    Remedies. Subject to any notice and cure period, upon the
occurrence of any Event of Default, the holder hereof may, at its option, (i)
declare the entire unpaid balance of principal and accrued but unpaid interest
on this Note to be immediately due and payable, (ii) refuse to advance any
additional amounts under this Note, (iii) foreclose all liens securing payment
hereof, (iv) pursue any and all other rights, remedies and recourses available
to the holder hereof, including but not limited to, any such rights, remedies or
recourses under the Loan Documents, at law or in equity, or (v) pursue any
combination of the foregoing.

         17.    Spreading. Any provision herein, or in any document securing
this Note, or any other document executed or delivered in connection herewith,
or in any other agreement or commitment, whether written or oral, expressed or
implied, to the contrary notwithstanding, neither Bank nor any holder hereof
shall in any event be entitled to receive or collect, nor shall or may amounts
received hereunder be credited, so that Bank or any holder hereof shall be paid,
as interest, a sum greater than the maximum amount permitted by applicable law
to be charged to the person, partnership, firm or corporation primarily
obligated to pay this Note at the time in question. If any construction of this
Note or any document securing this Note, or any and all other papers, agreements
or commitments, indicate a different right given to Bank or any holder hereof to
ask for, demand or receive any larger sum as interest, such is a mistake in
calculation or wording which this clause shall override and control, it being
the intention of the parties that this Note, and all other instruments securing
the payment of this Note or executed or delivered in connection herewith shall
in all things comply with the applicable law and proper adjustments shall
automatically be made accordingly. In the event that Bank or any holder hereof
ever receives, collects or applies as interest, any sum in excess of the Maximum
Rate, if any, such excess amount shall be applied to the reduction of the unpaid
principal balance of this Note, and if this Note is paid in full, any remaining
excess shall be paid to Borrower. In determining whether or not the interest
paid or payable, under any specific contingency, exceeds the Maximum Rate, if
any, Borrower and Bank or any holder hereof shall, to the maximum extent
permitted under applicable law: (a) characterize any nonprincipal payment as an
expense or fee

                                                                          Page 9

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rather than as interest, (b) exclude voluntary prepayments and the effects
thereof, (c) "spread" the total amount of interest throughout the entire term of
this Note; provided that if this Note is paid and performed in full prior to the
end of the full contemplated term hereof, and if the interest received for the
actual period of existence thereof exceeds the Maximum Rate, if any, Bank or any
holder hereof shall refund to Borrower the amount of such excess, or credit the
amount of such excess against the aggregate unpaid principal balance of all
advances made by the Bank or any holder hereof under this Note at the time in
question.

         18.    Choice of Law. This Note is being executed and delivered, and is
intended to be performed in the State of Texas. Except to the extent that the
laws of the United States may apply to the terms hereof, the substantive laws of
the State of Texas shall govern the validity, construction, enforcement and
interpretation of this Note. In the event of a dispute involving this Note or
any other instruments executed in connection herewith, the undersigned
irrevocably agrees that venue for such dispute shall lie in any court of
competent jurisdiction in Dallas County, Texas.

         19.    This Note is given in renewal and extension, but not
extinguishment, of all amounts left owing and unpaid on that certain Amended and
Restated Borrowing Base Note dated as of September 14, 2001 executed and
delivered by Borrower and payable to the order of Bank in the stated principal
amount of $14,000,000 (the "Existing Note") and the principal balance of the
Existing Note is outstanding on the date hereof under this Note.

                                        BORROWER:

                                        AMX CORPORATION, a Texas corporation,

                                        By: /s/ Jean M. Nelson
                                           ------------------------------------
                                        Name: Jean M. Nelson
                                             ----------------------------------
                                        Title: VP & CFO
                                              ---------------------------------

                                                                         Page 10<PAGE>

                                                                    EXHIBIT 10.4

                              TERM PROMISSORY NOTE

$1,532,175.00                                                 September 30, 2002

         FOR VALUE RECEIVED, on or before April 30, 2004 ("Maturity Date") the
undersigned and if more than one, each of them, jointly and severally
("Borrower"), does hereby unconditionally promise to pay to the order of BANK
ONE, NA, a national banking association ("Bank"), at its offices in Dallas
County, Texas at 1717 Main Street, Dallas, Texas 75201, the principal amount of
ONE MILLION FIVE HUNDRED THIRTY-TWO THOUSAND ONE HUNDRED SEVENTY-FIVE AND NO/100
DOLLARS ($1,532,175.00) ("Total Principal Amount"), or such amount less than the
Total Principal Amount which is outstanding from time to time if the total
amount outstanding under this Term Promissory Note (this "Note") is less than
the Total Principal Amount, in lawful money of the United States of America,
together with interest on such portion of the Total Principal Amount which has
been drawn until paid at the rates per annum provided below.

         1.    Definitions. For purposes of this Note, unless the context
otherwise requires, the following terms shall have the definitions assigned to
such terms as follows:

2        "Adjusted LIBOR Rate" shall mean with respect to each Interest Period,
on any day thereof an amount equal to the sum of (i) the quotient of (a) the
LIBOR Rate with respect to such Interest Period (the "Index"), divided by (b)
the remainder of 1.0 less the Reserve Requirement in effect on such day, plus
(ii) 2.25%. Each determination by Bank of the Adjusted LIBOR Rate shall, in the
absence of manifest error, be conclusive and binding.

         "Business Day" shall mean any day other than a Saturday, Sunday or any
other day on which national banking associations are authorized to be closed.

         "Consequential Loss" shall mean, with respect to Borrower's payment of
all or any portion of the then outstanding principal amount of any LIBOR Balance
on a day other than the last day of the Interest Period related thereto, any
loss, cost or expense incurred by Bank in redepositing such principal amount,
including the sum of (i) the interest which, but for such payment, Bank would
have earned in respect of such principal amount so paid, for the remainder of
the Interest Period applicable to such sum, reduced, if Bank is able to
redeposit such principal amount so paid for the balance of such Interest Period,
by the interest earned by Bank as a result of so redepositing such principal
amount plus (ii) any expense or penalty incurred by Bank on redepositing such
principal amount.

         "Contract Rate" shall mean a rate of interest based upon the Adjusted
LIBOR Rate or the Prime Rate in effect at any time pursuant to an Interest
Notice.

         "Dollars" shall mean lawful currency of the United States of America.

         "Event of Default" shall mean the occurrence of an event of default
specified in the Loan Agreement (as hereinafter defined).

                                                                          Page 1

<PAGE>

         "Excess Interest Amount" shall mean, on any date, the amount by which
(i) the amount of all interest which would have accrued prior to such date on
the principal of this Note, had the applicable Contract Rate at all times been
in effect without limitation by the Maximum Rate, exceeds (ii) the aggregate
amount of interest accrued on this Note on or prior to such date.

         "Interest Notice" shall mean the notice given by Borrower to Bank of
the Interest Options selected hereunder. Each Interest Notice shall specify the
Interest Option selected, the amount of the unpaid principal balance of this
Note to bear interest at the rate selected and, if the Adjusted LIBOR Rate is
specified, the length of the applicable Interest Period. An Interest Notice may
be written or oral (if promptly confirmed thereafter in writing) and Bank is
hereby authorized and directed to honor all telephonic Interest Notices from any
person authorized to request advances hereunder.

         "Interest Option" shall have the meaning assigned to such term in
paragraph 6 hereof.

         "Interest Payment Date" shall mean (i) in the case of the Prime Rate
Balance, on the last day of December, 2002 and on the last day of March, June,
September and December thereafter, and on the Maturity Date, and (ii) in the
case of any LIBOR Balance, on the earlier of (a) the last day of the
corresponding Interest Period with respect to such LIBOR Balance, or (b) the
last day of December, 2002, and on the last day of March, June, September and
December thereafter, and on the Maturity Date.

         "Interest Period" shall mean each consecutive one month, two month and
three month period (the first of which shall commence on the date of this Note)
effective as of the first day of each Interest Period and ending on the last day
of each Interest Period, provided that if any Interest Period is scheduled to
end on a date for which there is no numerical equivalent to the date on which
the Interest Period commenced, then it shall end instead on the last day of such
calendar month.

         "LIBOR Balance" shall mean any principal balance of this Note which,
pursuant to an Interest Notice, bears interest at a rate based upon the Adjusted
LIBOR Rate for the Interest Period specified in such Interest Notice.

         "LIBOR Rate" shall mean the offered rate for U.S. Dollar deposits of
not less than $100,000.00 for a period of time equal to each Interest Period as
of 11:00 A.M. City of London, England time two London Business Days prior to the
first date of each Interest Period of this Note as shown on the display
designated as "British Bankers Assoc. Interest Settlement Rates" on the Telerate
System ("Telerate"), Page 3750 or Page 3740, or such other page or pages as may
replace such pages on Telerate for the purpose of displaying such rate.
Provided, however, that if such rate is not available on Telerate then such
offered rate shall be otherwise independently determined by Bank from an
alternate, substantially similar independent source available to Bank or shall
be calculated by Bank by a substantially similar methodology as that theretofore
used to determine such offered rate in Telerate. Each change in the rate to be
charged on this Note will become effective without notice on the commencement of
each Interest Period based upon the Index then in effect.

         "Loan Agreement" shall mean that certain Letter Loan Agreement by and
between Bank and Borrower dated September 30, 2002, as amended from time to
time.

                                                                          Page 2

<PAGE>

         "Loan Documents" shall mean this Note, the Revolving Note (as defined
in the Loan Agreement), the EXIM Loan Documents (as defined in the Loan
Documents), the Loan Agreement and all other documents evidencing, securing,
governing, guaranteeing and/or pertaining to the Loan Agreement.

         "London Business Day" means any day other than a Saturday, Sunday or a
day on which banking institutions are generally authorized or obligated by law
or executive order to close in the City of London, England.

         "Maximum Rate" shall mean, with respect to the holder hereof, the
maximum nonusurious interest rate, if any, that at any time, or from time to
time, may be contracted for, taken, reserved, charged, or received on the
indebtedness evidenced by this Note under the laws which are presently in effect
in the United States and the State of Texas applicable to such holder and such
indebtedness or, to the extent permitted by law, under such applicable laws of
the United States and the State of Texas which may hereafter be in effect and
which allow a higher maximum nonusurious interest rate than applicable laws now
allow. To the extent that Chapter 303 of the Texas Finance Code ("Code"), is
relevant to any holder of this Note for the purposes of determining the Maximum
Rate, each such holder elects to determine such applicable legal rate under the
Act pursuant to the "weekly ceiling," from time to time in effect, as referred
to and defined in Chapter 303 of the Code; subject, however, to the limitations
on such applicable ceiling referred to and defined in Chapter 303 of the Code,
and further subject to any right such holder may have subsequently, under
applicable law, to change the method of determining the Maximum Rate. If no
Maximum Rate is established by applicable law, then the Maximum Rate shall be
equal to eighteen percent (18%).

         "Prime Rate" shall mean the rate established from time to time by Bank
as its prime rate of interest (which may not be the lowest, best or most
favorable rate of interest which Bank may charge on loans to its customers).

         "Prime Rate Balance" shall mean that portion of the principal balance
of this Note bearing interest at a rate based upon the Prime Rate.

         "Principal Payment Date" shall mean on the last day of December, 2002
and on the last day of March, 2003, June, 2003, September, 2003, and December,
2003, and on the Maturity Date.

         "Regulation D" shall mean Regulation D of the Board of Governors of the
Federal Reserve System from time to time in effect and shall include any
successor or other regulation relating to reserve requirements applicable to
member banks of the Federal Reserve System.

         "Reserve Requirement" shall, on any day, mean that percentage
(expressed as a decimal fraction) which is in effect on such day, as provided by
the Board of Governors of the Federal Reserve System (or any successor
governmental body) for determining the reserve requirements (including without
limitation, basic, supplemental, marginal and emergency reserves) under
Regulation D with respect to "Eurocurrency liabilities" as currently defined in
Regulation D, or under any similar or successor regulation. For purposes of this
definition, any LIBOR Balances hereunder shall be deemed "Eurocurrency
liabilities" under Regulation D without benefit of or credit

                                                                          Page 3

<PAGE>

for prorations, exemptions or offsets under Regulation D. Bank's determination
of the Reserve Requirement shall be conclusive, in the absence of manifest
error.

         2.    Payments of Interest and Principal. Interest on the unpaid
principal balance of this Note shall be due and payable on each Interest Payment
Date as it accrues. In addition to the foregoing interest payments, on each
Principal Payment Date, Borrower shall pay to Bank a payment of principal in the
amount of 1/6th of the stated face amount of this Note. The entire unpaid
principal balance of this Note, and all accrued but unpaid interest thereon,
shall be due and payable on the Maturity Date.

         3.    Rates of Interest. The unpaid principal of the Prime Rate Balance
shall bear interest at a rate per annum which shall from day to day be equal to
the lesser of (i) the Prime Rate in effect from day to day, or (ii) the Maximum
Rate. The unpaid principal of each LIBOR Balance shall bear interest at a rate
per annum which shall from day to day be equal to the lesser of (i) the Adjusted
LIBOR Rate for the Interest Period in effect with respect to such LIBOR Balance,
or (ii) the Maximum Rate. Each change in the interest rate applicable to a Prime
Rate Balance shall become effective without prior notice to Borrower
automatically as of the opening of business on the date of such change in the
Prime Rate. Interest on this Note shall be calculated on the basis of the actual
days elapsed in a year consisting of 360 days.

         4.    Interest Recapture. If on each Interest Payment Date or any other
date on which interest payments are required hereunder, Bank does not receive
interest on this Note computed at the Contract Rate because such Contract Rate
exceeds or has exceeded the Maximum Rate, then Borrower shall, upon the written
demand of Bank, pay to Bank in addition to the interest otherwise required to be
paid hereunder, on each Interest Payment Date thereafter, the Excess Interest
Amount (calculated as of such later Interest Payment Date); provided that in no
event shall Borrower be required to pay, for any Interest Period, interest at a
rate exceeding the Maximum Rate effective during such period.

         5.    Interest on Past Due Amounts. To the extent any interest is not
paid on or before the fifth day after it becomes due and payable, Bank may, at
its option, add such accrued but unpaid interest to the principal of this Note.
Notwithstanding anything herein to the contrary, upon an Event of Default or at
maturity, whether by acceleration or otherwise, all principal of this Note
shall, at the option of Bank, bear interest at the Prime Rate plus 4% (the
"Default Rate") until paid; provided, however, the Default Rate shall at no time
exceed the Maximum Rate.

         6.    Interest Option. Subject to the provisions hereof, Borrower shall
have the option (an "Interest Option") of having designated portions of the
unpaid principal balance of this Note bear interest at a rate based upon the
Adjusted LIBOR Rate or Prime Rate as provided in paragraph 3 hereof, provided,
however, that the selection of the Adjusted LIBOR Rate for a particular Interest
Period shall not be for less than $100,000.00 of unpaid principal or an integral
multiple thereof. The Interest Option shall be exercised in the manner provided
below:

               (i)    At Closing. Borrower shall give Bank an Interest Notice
         indicating the initial Interest Option selected with respect to the
         principal balance hereof.

                                                                          Page 4

<PAGE>

               (ii)   At Expiration of Interest Periods. Unless otherwise agreed
         to by Bank, at least two (2) Business Days prior to the termination of
         any Interest Period, Borrower shall give Bank an Interest Notice
         indicating the Interest Option to be applicable to the corresponding
         LIBOR Balance upon the expiration of such Interest Period. If the
         required Interest Notice shall not have been timely received by Bank
         prior to the expiration of the then-relevant Interest Period, Borrower
         shall be deemed to have selected a rate based upon the Prime Rate to be
         applicable to such LIBOR Balance upon the expiration of such Interest
         Period and to have given Bank notice of such selection.

               (iii)  Conversion From Prime Rate. During any period in which any
         portion of the principal hereof bears interest at a rate based upon the
         Prime Rate, Borrower shall have the right, on any London Business Day
         (the "Conversion Date"), to convert all or a portion of such principal
         amount from the Prime Rate Balance to a LIBOR Balance by giving Bank an
         Interest Notice of such selection at least two (2) London Business Days
         prior to such Conversion Date, or as otherwise agreed to by Bank.

An Interest Notice may be written or oral and Bank is hereby authorized and
directed to honor all telephonic Interest Notices hereunder. Borrower agrees to
indemnify and hold Bank harmless from any loss or liability incurred by Bank in
connection with honoring any telephonic or other oral Interest Notices. All
written Interest Notices are effective only upon receipt by Bank. Each Interest
Notice shall be irrevocable and binding upon Borrower.

         7.    Special Provisions For LIBOR Pricing.

               a.     Inadequacy of LIBOR Loan Pricing. If Bank determines that,
by reason of circumstances affecting the interbank eurodollar market generally,
deposits in Dollars (in the applicable amounts) are not being offered to United
States financial institutions in the interbank eurodollar market for such
Interest Period, or that the rate at which such Dollar deposits are being
offered will not adequately and fairly reflect the cost to Bank of making or
maintaining a LIBOR Balance for the applicable Interest Period, Bank shall
forthwith give notice thereof to Borrower, whereupon until Bank notifies
Borrower that the circumstances giving rise to such suspension no longer exist,
(i) the right of Borrower to select an Interest Option based upon the LIBOR Rate
shall be suspended, and (ii) Borrower shall be deemed to have converted each
LIBOR Balance to the Prime Rate Balance in accordance with the provisions hereof
on the last day of the then-current Interest Period applicable to such LIBOR
Balance.

               b.     Illegality. If the adoption of any applicable law, rule or
regulation, or any change therein, or any change in the interpretation or
administration thereof by any governmental authority, central bank or comparable
agency charged with the interpretation or administration thereof, or compliance
by Bank with any request or directive (whether or not having the force of law)
of any such authority, central bank or comparable agency shall make it unlawful
or impossible for Bank to make or maintain a LIBOR Balance, Bank shall so notify
Borrower. Upon receipt of such notice, Borrower shall be deemed to have
converted any LIBOR Balance to the Prime Rate Balance, on either (i) the last
day of the then-current Interest Period applicable to such LIBOR Balance if Bank
may lawfully continue to maintain and fund such LIBOR Balance to such day, or
(ii) immediately, if Bank may not lawfully continue to maintain such LIBOR
Balance to such day.

                                                                          Page 5

<PAGE>

         8.    Extension, Place and Application of Payments. Should the
principal of, or any interest on, this Note become due and payable on any day
other than a Business Day, the maturity thereof shall be extended to the next
succeeding Business Day, and interest shall be payable with respect to such
extension. All payments of principal of, and interest on, this Note shall be
made in lawful money of the United States of America in immediately available
funds. Payments made to Bank by Borrower hereunder shall be applied first to
accrued but unpaid interest and then to outstanding principal.

         9.    Loan Agreement. This Note is subject to the terms and provisions
of the Loan Agreement, which is incorporated herein by reference for all
purposes. The holder of this Note is entitled to the benefits provided in the
Loan Agreement.

         10.   Prepayments, Consequential Loss. Any prepayment made hereunder
shall be made together with all interest accrued but unpaid on this Note through
the date of such prepayment. Contemporaneously with each prepayment of
principal, Borrower shall give Bank written or oral notice indicating whether
such prepayment is to be applied to the Prime Rate Balance or a particular LIBOR
Balance. If such notice is not timely received by Bank, Borrower shall be deemed
to have selected to prepay the Prime Rate Balance and, if any sums remain after
satisfying all of the Prime Rate Balance, the remaining sums shall be applied to
any LIBOR Balance(s) that Bank determines in its sole discretion. Borrower
agrees to indemnify and hold Bank harmless from any loss or liability incurred
by Bank in connection with honoring telephonic or other oral notices indicating
how a prepayment is to be applied. If Borrower makes any such prepayment other
than on the last day of an Interest Period, Borrower shall pay all accrued
interest on the principal amount prepaid with such prepayment and, on demand,
shall reimburse Bank and hold Bank harmless from all losses and expenses
incurred by Bank as a result of such prepayment, including, without limitation,
any losses and expenses arising from the liquidation or reemployment of deposits
acquired to fund or maintain the principal amount prepaid. Such reimbursement
shall be calculated as though Bank funded the principal amount prepaid through
the purchase of U.S. Dollar deposits in the London, England interbank market
having a maturity corresponding to such Interest Period and bearing an interest
rate equal to the LIBOR Rate for such Interest Period, whether in fact that is
the case or not. Bank's determination of the amount of such reimbursement shall
be conclusive in the absence of manifest error.

         11.   Additional Costs. Borrower agrees to pay to Bank all Additional
Costs within ten (10) days of receipt by Borrower from Bank of a statement
setting forth the amount or amounts due and the basis for the determination from
time to time of such amount or amounts, which statement shall be conclusive and
binding upon Borrower absent manifest error. Failure on the part of Bank to
demand compensation for any Additional Costs in any Interest Period shall not
constitute a waiver of Bank's right to demand compensation for any Additional
Costs incurred during any such Interest Period or in any other subsequent or
prior Interest Period. The term "Additional Costs" shall mean such additional
amount or amounts as Bank shall reasonably determine will compensate Bank for
actual costs incurred by Bank in maintaining LIBOR Rates on the LIBOR Balances
or any portion thereof as a result of any change, after the date of this Note,
in applicable law, rule or regulation or in the interpretation or administration
thereof by, or the compliance by Bank with any request or directive from, any
domestic or foreign governmental authority charged with the interpretation or
administration thereof (whether or not having the force of law) or by any
domestic or foreign court

                                                                          Page 6

<PAGE>

changing the basis of taxation of payments to Bank of the LIBOR Balances or
interest on the LIBOR Balances or any portion thereof at an Adjusted LIBOR Rate
or any other fees or amounts payable under this Note or the Loan Agreement
(other than taxes imposed on all or any portion of the overall net income of
Bank by the State of Texas or the Federal government), or imposing, modifying or
applying any reserve, special deposit or similar requirement against assets of,
deposits with or for the account of, credit extended by, or any other
acquisition of funds for loans by Bank, or imposing on Bank, as the case may be,
or on the London interbank market any other condition affecting this Note, the
Loan Agreement or the LIBOR Balances so as to increase the cost of Bank making
or maintaining Adjustable LIBOR Rates with respect to the LIBOR Balances or any
portion thereof or to reduce the amount of any sum received or receivable by
Bank under this Note or the Loan Agreement (whether of principal, interest or
otherwise), by an amount deemed by Bank in good faith to be material, but
without duplication for Reserve Requirement. Bank agrees that it will not demand
compensation for any Additional Costs from Borrower unless it is seeking similar
compensation from its other customers similarly situated.

         12.   Notices. Except as otherwise specified herein, all notices and
requests required or permitted hereunder shall be in writing and shall be deemed
to have been given when personally delivered or, if mailed, two Business Days
after deposited in a regularly maintained receptacle for the United States
Postal Service, postage prepaid, registered or certified, return receipt
requested, addressed to Borrower or Bank at the following respective addresses
or such other address as such party may from time to time designate by written
notice to the other: Borrower: 3000 Research Drive, Richardson, Texas 75082,
Attention: Jean Nelson; Bank: 1717 Main Street, Dallas, Texas 75201, Attention:
Frederick A. Points.

         13.   Legal Fees. If this Note is placed in the hands of any attorney
for collection, or if it is collected through any legal proceeding at law or in
equity or in bankruptcy, receivership or other court proceedings, Borrower
agrees to pay all costs of collection including, but not limited to, court costs
and reasonable attorneys' fees.

         14.   Waivers. Borrower and each surety, endorser, guarantor and any
other party ever liable for payment of any sums of money payable on this Note,
jointly and severally waive presentment and demand for payment, protest, notice
of protest, intention to accelerate, acceleration and non-payment, or other
notice of default, and agree that their liability under this Note shall not be
affected by any renewal or extension in the time of payment hereof, or in any
indulgences, or by any release or change in any security for the payment of this
Note, and hereby consent to any and all renewals, extensions, indulgences,
releases or changes, regardless of the number of such renewals, extensions,
indulgences, releases or changes; provided, however, this Note may not be
amended or modified except by a written instrument signed by the Borrower and
the holder hereof.

         No waiver by Bank of any of its rights or remedies hereunder or under
any other document evidencing or securing this Note or otherwise shall be
considered a waiver of any other subsequent right or remedy of Bank; no delay or
omission in the exercise or enforcement by Bank of any rights or remedies shall
ever be construed as a waiver of any right or remedy of Bank; and no exercise or
enforcement of any such rights or remedies shall ever be held to exhaust any
right or remedy of Bank.

                                                                          Page 7

<PAGE>

         15.   Remedies. Subject to any notice and cure period, upon the
occurrence of any Event of Default, the holder hereof may, at its option, (i)
declare the entire unpaid balance of principal and accrued but unpaid interest
on this Note to be immediately due and payable, (ii) refuse to advance any
additional amounts under this Note, (iii) foreclose all liens securing payment
hereof, (iv) pursue any and all other rights, remedies and recourses available
to the holder hereof, including but not limited to, any such rights, remedies or
recourses under the Loan Documents, at law or in equity, or (v) pursue any
combination of the foregoing.

         16.   Spreading. Any provision herein, or in any document securing this
Note, or any other document executed or delivered in connection herewith, or in
any other agreement or commitment, whether written or oral, expressed or
implied, to the contrary notwithstanding, neither Bank nor any holder hereof
shall in any event be entitled to receive or collect, nor shall or may amounts
received hereunder be credited, so that Bank or any holder hereof shall be paid,
as interest, a sum greater than the maximum amount permitted by applicable law
to be charged to the person, partnership, firm or corporation primarily
obligated to pay this Note at the time in question. If any construction of this
Note or any document securing this Note, or any and all other papers, agreements
or commitments, indicate a different right given to Bank or any holder hereof to
ask for, demand or receive any larger sum as interest, such is a mistake in
calculation or wording which this clause shall override and control, it being
the intention of the parties that this Note, and all other instruments securing
the payment of this Note or executed or delivered in connection herewith shall
in all things comply with the applicable law and proper adjustments shall
automatically be made accordingly. In the event that Bank or any holder hereof
ever receives, collects or applies as interest, any sum in excess of the Maximum
Rate, if any, such excess amount shall be applied to the reduction of the unpaid
principal balance of this Note, and if this Note is paid in full, any remaining
excess shall be paid to Borrower. In determining whether or not the interest
paid or payable, under any specific contingency, exceeds the Maximum Rate, if
any, Borrower and Bank or any holder hereof shall, to the maximum extent
permitted under applicable law: (a) characterize any nonprincipal payment as an
expense or fee rather than as interest, (b) exclude voluntary prepayments and
the effects thereof, (c) "spread" the total amount of interest throughout the
entire term of this Note; provided that if this Note is paid and performed in
full prior to the end of the full contemplated term hereof, and if the interest
received for the actual period of existence thereof exceeds the Maximum Rate, if
any, Bank or any holder hereof shall refund to Borrower the amount of such
excess, or credit the amount of such excess against the aggregate unpaid
principal balance of all advances made by the Bank or any holder hereof under
this Note at the time in question.

         17.   Choice of Law. This Note is being executed and delivered, and is
intended to be performed in the State of Texas. Except to the extent that the
laws of the United States may apply to the terms hereof, the substantive laws of
the State of Texas shall govern the validity, construction, enforcement and
interpretation of this Note. In the event of a dispute involving this Note or
any other instruments executed in connection herewith, the undersigned
irrevocably agrees that venue for such dispute shall lie in any court of
competent jurisdiction in Dallas County, Texas.

         18.   This Note is given in renewal and extension, but not
extinguishment, of all amounts left owing and unpaid on that certain Amended and
Restated Term Note (Corrected) dated as of September 14, 2001 executed and
delivered by Borrower and payable to the order of Bank in the stated principal
amount of $2,553,625.27 (the "Existing Note") and the principal balance of the

                                                                          Page 8

<PAGE>

Existing Note (which is the face amount of this Note on the date hereof) is
outstanding on the date hereof under this Note.

                                           BORROWER:

                                           AMX CORPORATION, a Texas corporation,

                                           By: /s/ Jean M. Nelson
                                              ----------------------------------
                                           Name: Jean M. Nelson
                                                -------------------------------
                                           Title: VP & CFO
                                                 ------------------------------

                                                                          Page 9

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