Document:

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                                                                    EXHIBIT 4.18

                              REVOLVING CREDIT NOTE

                                  Dallas, Texas

$7,000,000.00                                                 September 30, 1999

         FOR VALUE RECEIVED, TIDEL ENGINEERING, L.P., a Delaware limited
partnership (herein called "Borrower"), promises to pay to the order of CHASE
BANK OF TEXAS, N.A., a national banking association (herein called "Payee"), at
2200 Ross Avenue, Dallas, Texas 75201, or at such other place as Payee may
hereafter designate in writing, in immediately available funds and in lawful
money of the United States of America, the principal sum of SEVEN MILLION AND
NO/100 DOLLARS ($7,000,000.00) (or the unpaid balance of all principal advanced
against this note, if that amount is less), together with interest on the unpaid
principal balance of this note from time to time outstanding until maturity on
September 30, 2001, at the rate or rates provided for in the Credit Agreement
and interest on all past due amounts at the Past Due Rate as provided in the
Credit Agreement; provided, that for the full term of this note, the interest
rate produced by the aggregate of all sums paid or agreed to be paid to the
holder of this note for the use, forbearance or detention of the debt evidenced
hereby shall not exceed the Highest Lawful Rate, if any, applicable to Payee.

         If, for any reason whatever, the interest paid or received on this note
during its full term produces a rate which exceeds the Highest Lawful Rate, if
any, applicable to Payee, the holder of this note shall refund to the payor or,
at the holder's option, credit against the principal of this note such portion
of said interest as shall be necessary to cause the interest paid on this note
to produce a rate equal to the Highest Lawful Rate, if any, applicable to payee.
All sums paid or agreed to be paid to the holder of this note for the use,
forbearance or detention of the indebtedness evidenced hereby shall, to the
extent permitted by applicable law, be amortized, prorated, allocated and spread
in equal parts throughout the full term of this note, so that the interest rate
is uniform throughout the full term of this note. To the extent the laws of the
State of Texas are applicable for purposes of determining the "Highest Lawful
Rate," such term shall mean the "weekly ceiling" from time to time in effect
under Chapter 303 of the Texas Finance Code, as amended, or if permitted by
applicable law and effective upon the giving of the notices required by Section
303.403 of the Texas Finance Code (or effective upon any other date otherwise
specified by applicable Law), the "monthly ceiling," the "quarterly ceiling," or
"annualized ceiling" from time to time in effect under such Chapter 303 of the
Texas Finance Code, whichever that Lender shall elect to substitute for the
"weekly ceiling," and vice versa, each such substitution to have the effect
provided in Chapter 303 of the Texas Finance Code; and Lender shall be entitled
to make such election from time to time and one or more times and, without
notice to Borrower, to leave any such substitute rate in effect for subsequent
periods in accordance with Chapter 303 of the Texas Finance Code. Pursuant
Section 346.004 of the Texas Finance Code, as amended, Borrower agrees that
Chapter 346 of the Texas Finance Code (which regulates certain revolving credit
loan accounts and revolving tri-party accounts) shall not govern or in any
manner apply to the Obligations.

REVOLVING CREDIT NOTE - Page 1

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         This note has been issued pursuant to the terms of that certain Credit
Agreement dated April 1, 1999, by and among Borrower, Payee and Tidel
Technologies, Inc., as amended by that certain First Amendment to Credit
Agreement dated the date hereof, by and among Borrower, Payee and Tidel
Technologies, Inc. (which, as it may be amended, restated, modified or
supplemented from time to time, is herein called the "Credit Agreement"), to
which reference is made for all purposes. This note is a Note under the terms of
the Credit Agreement, and advances against this note by Payee or other holder
hereof, payments and prepayments hereunder and acceleration hereof shall be
governed by the Credit Agreement. Capitalized words and phrases used herein and
not defined herein and which are defined in the Credit Agreement shall have the
same meanings herein as are ascribed to them in the Credit Agreement.

         The unpaid principal balance of this note at any time shall be the
total of all principal lent or advanced against this note less the sum of all
principal payments and permitted prepayments made on this note by or for the
account of Borrower. All loans and advances and all payments and permitted
prepayments made hereon may be endorsed by the holder of this note on the
schedule which is attached hereto (and hereby made a part hereof for all
purposes) or otherwise recorded in the holder's records; provided, that any
failure to make notation of (a) any advance shall not cancel, limit or otherwise
affect Borrower's obligations or any holder's rights with respect to that
advance, or (b) any payment or permitted prepayment of principal shall not
cancel, limit or otherwise affect Borrower's entitlement to credit for that
payment as of the date received by the holder.

         Borrower and any and all co-makers, endorsers, guarantors and sureties
severally waive notice (including, but not limited to, notice of intent to
accelerate and notice of acceleration, notice of protest and notice of
dishonor), demand, presentment for payment, protest, diligence in collecting and
the filing of suit for the purpose of fixing liability and consent that the time
of payment hereof may be extended and re-extended from time to time without
notice to any of them. Each such person agrees that his, her or its liability on
or with respect to this note shall not be affected by any release of or change
in any guaranty or security at any time existing or by any failure to perfect or
maintain perfection of any lien against or security interest in any such
security or the partial or complete unenforceability of any guaranty or other
surety obligation, in each case in whole or in part, with or without notice and
before or after maturity.

         THIS NOTE SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE
LAWS OF THE STATE OF TEXAS (OTHER THAN THE CONFLICTS OF LAWS PRINCIPLES THEREOF)
AND THE UNITED STATES OF AMERICA FROM TIME TO TIME IN EFFECT.

REVOLVING CREDIT NOTE - Page 2

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         This note is a renewal, modification and rearrangement, and not a
novation or extinguishment, of that certain Revolving Credit Note dated May 27,
1998, executed by Tidel Engineering, Inc., the non-surviving entity of the
merger between Tidel Engineering, Inc. and the Borrower, payable to the order of
Payee, in the original principal amount of $7,000,000.00, and that certain
Revolving Credit Note dated April 1, 1999, executed by Borrower, payable to the
order of Payee, in the original principal amount of $7,000,000.00 (collectively,
the "Prior Notes"). All rights, titles, liens and security interests securing
the Prior Notes are preserved, maintained and carried forward to secure this
note.

                              TIDEL ENGINEERING, L.P.,
                              a Delaware limited partnership

                              By: Tidel Cash Systems, Inc., its general partner

                                   By:
                                      -----------------------------------------
                                      Mark K. Levenick,
                                      President and Chief Executive Officer

REVOLVING CREDIT NOTE - Page 3<PAGE>   1
                                                                    EXHIBIT 4.19

                       FIRST AMENDMENT TO CREDIT AGREEMENT

         This First Amendment to Credit Agreement (this "Amendment") is made and
entered into as of September 30, 1999, by and among CHASE BANK OF TEXAS, N.A., a
national banking association ("Lender"), TIDEL ENGINEERING, L.P. ("Borrower"), a
Delaware limited partnership, and TIDEL TECHNOLOGIES, INC., a Delaware
corporation ("Ultimate Parent").

                                R E C I T A L S:

         A. On April 1, 1999, Lender, Borrower, and Ultimate Parent entered into
that certain Credit Agreement (the "Credit Agreement") pursuant to which Lender
agreed to make loans and advances (collectively the "Loans") to Borrower and
Ultimate Parent in accordance with the terms thereof. The Loans are evidenced by
that certain Revolving Credit Note of even date with the Credit Agreement, in
the stated principal amount of $7,000,000.00, and that certain Term Note of even
date with the Credit Agreement, in the stated principal amount of $544,000.00,
each bearing interest and being payable to the order of Lender as therein
provided (collectively, the "Notes"). The Credit Agreement, the Notes and the
documents, instruments and agreements executed in connection therewith are
collectively referred to herein as the "Loan Documents".

         B. Borrower has requested Lender to extend the term of the Credit
Agreement and to modify the minimum Tangible Net Worth requirement of Section
8.12 of the Credit Agreement.

         C. Lender, at the request of Borrower, for good and valuable
consideration, is willing to enter into this Amendment upon the terms and
conditions set forth below:

                               A G R E E M E N T:

         NOW, THEREFORE, for and in consideration of Ten and No/100 Dollars
($10.00) and other good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, Borrower and Lender hereby covenant and agree
as follows:

         1. Defined Terms. Capitalized terms used but not otherwise defined
herein shall have the meanings given to them in the Credit Agreement.

         2. Eligible Receivables. Clause (d) of the definition of "Eligible
Receivables" in Section 1.1 of the Credit Agreement is hereby amended to read in
its entirety as follows:

         (d) the total Receivables owing to the Borrower by the applicable
         account debtor constitute 10% or less of the aggregate Receivables
         owing to the Borrower by all account debtors, or if the total
         Receivables of the applicable account debtor (other than Credit Card
         Center, in which case 20%, and CardPro, Inc./CardTronics, in which case
         15%) exceed 10% of the aggregate of all Receivables owing to the
         Borrower and its Subsidiaries by all account debtors, the Receivables
         of the applicable account debtor up

FIRST AMENDMENT - Page 1

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         to such respective percentage limit shall be deemed to constitute
         Eligible Receivables (subject to compliance with all other applicable
         standards of eligibility) and the Receivables of the applicable account
         debtor exceeding such respective percentage limit shall be included
         within Eligible Receivables (subject to compliance with all other
         applicable standards of eligibility) only if the Receivables exceeding
         such respective percentage limit are backed or secured by credit
         insurance reasonably satisfactory to the Lender in all respects and
         such credit insurance has been assigned to the Lender upon terms
         reasonably acceptable to the Lender in its discretion;

         3. Revolving Loan Maturity Date. The definition of "Revolving Loan
Maturity Date" in Section 1.1 of the Credit Agreement is hereby amended to read
in its entirety as follows:

                  Revolving Loan Maturity Date shall mean the earlier of (a)
         September 30, 2001, (b) any date that the Revolving Commitment is
         terminated in full by the Borrower pursuant to Section 2.4 hereof, and
         (c) any date the Revolving Loan Maturity Date is accelerated by the
         Lender pursuant to Section 9.1 hereof.

         4. Tangible Net Worth. Section 8.12 of the Credit Agreement is hereby
amended to read in its entirety as follows:

                  8.12 Tangible Net Worth. Permit the Tangible Net Worth of the
         Borrower (expressly excluding Ultimate Parent, its Subsidiaries and
         Borrower's Subsidiaries), as determined at any time and from time to
         time, to be less than the sum of the following:

                  (i)  $11,000,000.00; plus

                  (ii) the amount, which shall be added to clause (i) above as
         of the end of each calendar month, on a cumulative basis, beginning
         with the calendar month beginning October 1, 1998 and continuing each
         calendar month thereafter through the term of this Agreement, that is
         equal to the sequential monthly calculations of fifty percent (50%) of
         the positive (but not the negative) net income of the Borrower for each
         calendar month, beginning on and after October 1, 1998 (it being
         acknowledged that such calculations for calendar months prior to April
         1, 1999 shall be made with respect to Tidel Engineering, Inc., the
         predecessor-in-interest to the Borrower); plus

                  (iii) the amount of all capital contributions to Borrower on
         or after October 1, 1998 (it being acknowledged that such calculations
         for calendar months prior to April 1, 1999 shall be made with respect
         to Tidel Engineering, Inc., the predecessor-in-interest to the
         Borrower, and shall be made with respect to the amount of consideration
         received in exchange for equity interests issued by Tidel Engineering,
         Inc. during the applicable period of time).

         5. Exhibit D. Exhibit D to the Credit Agreement is hereby deleted in
its entirety and replaced with Exhibit D attached hereto.

FIRST AMENDMENT - Page 2

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         6. Exhibit H. Exhibit H to the Credit Agreement is hereby deleted in
its entirety and replaced with Exhibit H attached hereto.

         7. Conditions Precedent. The effectiveness of this Amendment is subject
to the satisfaction of the following conditions precedent, unless specifically
waived in writing by Lender:

                  (a) Lender shall have received a Revolving Credit Note, in
         form and substance satisfactory to Lender, duly executed by the
         Borrower;

                  (b) The representations and warranties contained herein and in
         all Loan Documents, as amended hereby, shall be true and correct in all
         material respects as of the date hereof as if made on the date hereof;
         and

                  (c) No Event of Default by Borrower or Ultimate Parent under
         the Loan Documents, as amended hereby, as of the date hereof, shall
         have occurred and be continuing and no event or conditions shall have
         occurred that with the giving of notice or lapse of time or both would
         be an Event of Default by Borrower or Ultimate Parent under the Loan
         Documents, as amended hereby, as of the date hereof, unless such Event
         of Default has been specifically waived in writing by Lender.

         8. Costs and Expenses. Borrower agrees to reimburse Lender for Lender's
costs and expenses, including, but not limited to, reasonable attorneys' fees
and legal expenses, incurred by Lender in connection with the preparation of
this Amendment and in connection with the negotiation and consummation of the
transaction contemplated hereby.

         9. The Credit Agreement. All references to the Credit Agreement in the
Loan Documents shall be deemed to be the Credit Agreement, as modified hereby.
Borrower expressly promises to perform all of its obligations under the Credit
Agreement and other Loan Documents, as modified by this Amendment.

         10. Acknowledgments of Borrower and Ultimate Parent. Borrower and
Ultimate Parent each hereby acknowledge and agree that (a) Lender is not in
default in the performance of its obligations under the Loan Documents; (b)
Borrower and Ultimate Parent have no claims, counterclaims, offsets, credits or
defenses to the Loan Documents and the performance of their respective
obligations thereunder, or if Borrower or Ultimate Parent have any such claims,
counterclaims, offsets, credits or defenses to the Loan Documents or any
transaction related to the Loans and/or the Loan Documents, same are hereby
waived, relinquished and released in consideration of Lender's execution and
delivery of this Amendment; (c) all of the provisions of the Loan Documents,
except as amended hereby, are in full force and effect; and (d) upon the
execution hereof, the Credit Agreement, the Notes, and the other Loan Documents,
as amended herein, are not in default by Borrower or Ultimate Parent.

         11. Full Force and Effect. Except as expressly modified and amended in
this Amendment, all of the terms, provisions and conditions of the Credit
Agreement, the Notes, and

FIRST AMENDMENT - Page 3

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all other Loan Documents are and shall remain in full force and effect and are
incorporated herein by reference.

         12. Counterparts. This Amendment may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed and delivered shall be deemed to be an original, and all of
which taken together shall constitute but one and the same instrument.

         13. No Oral Agreements. THIS AMENDMENT AND THE OTHER LOAN DOCUMENTS
EMBODY THE ENTIRE AGREEMENT AMONG THE PARTIES AND SUPERSEDES ALL PRIOR
AGREEMENTS AND UNDERSTANDINGS, IF ANY, RELATING TO THE SUBJECT MATTER HEREOF.
THIS WRITTEN AMENDMENT REPRESENTS THE FINAL AGREEMENT AMONG THE PARTIES AND MAY
NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO ORAL AGREEMENTS AMONG THE PARTIES.

FIRST AMENDMENT - Page 4

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         IN WITNESS WHEREOF, the parties have executed this First Amendment to
Credit Agreement as of the day and year first above written.

                                     LENDER:

                                     CHASE BANK OF TEXAS, N.A.,
                                     a national banking association

                                     By:
                                        ----------------------------------------
                                         Joanne Bramanti, Vice President

                                     BORROWER:

                                     TIDEL ENGINEERING, L.P.,
                                     a Delaware limited partnership

                                     By:      Tidel Cash Systems, Inc., its sole
                                              general partner

                                              By:
                                                 -------------------------------
                                                 Mark K. Levenick,
                                                 President and Chief Executive
                                                 Officer

                                     ULTIMATE PARENT:

                                     TIDEL TECHNOLOGIES, INC.,
                                     a Delaware corporation

                                     By:
                                        ----------------------------------------
                                          Mark K. Levenick,
                                          Chief Operating Officer

FIRST AMENDMENT - Page 5

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         By its execution below, each of Tidel Technologies, Inc., a Delaware
corporation, Tidel Services Inc., a Delaware corporation, and Tidel Cash
Systems, Inc., a Delaware corporation (each individually, a "Guarantor"),
acknowledges and consents to all of the terms and conditions of this Amendment,
and ratifies and confirms its respective Guaranty to and for the benefit of
Lender. Each Guarantor acknowledges that such Guarantor has no claims,
counterclaims, offsets, credits or defenses to the Loan Documents and the
performance of its obligations thereunder, or if such Guarantor does have any
such claims, counterclaims, offsets, credits or defenses to the Loan Documents
or any transaction related to the Loans and/or the Loan Documents, same are
hereby waived, relinquished and released in consideration of Lender's execution
and delivery of this Amendment. Further, each Guarantor agrees that nothing
contained in this Amendment shall adversely affect any right or remedy of Lender
under its respective Guaranty and that with respect to such Guaranty, all
references in such Guaranty to the "Obligations" shall mean the "Obligations",
as amended by this Amendment; that the execution and delivery of this Amendment
shall in no way change or modify such Guarantor's obligations as Guarantor
pursuant to its Guaranty; and that the execution and delivery of any agreements
by Borrower and Lender in connection with this Amendment shall not constitute a
waiver by Lender of any of Lender's rights against any Guarantor.

                                        TIDEL TECHNOLOGIES, INC.,
                                        a Delaware corporation

                                        By:
                                           -------------------------------------
                                           Mark K. Levenick,
                                           Chief Operating Officer

                                        TIDEL SERVICES, INC.,
                                        a Delaware corporation

                                        By:
                                           -------------------------------------
                                           Andrew Panaccione, Vice President

                                        TIDEL CASH SYSTEMS, INC.,
                                        a Delaware corporation

                                        By:
                                           -------------------------------------
                                           Mark K. Levenick, President and Chief
                                                Executive Officer

FIRST AMENDMENT - Page 6

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