<PAGE>   1
                                                                    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

<PAGE>   2


         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

<PAGE>   3


         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