<PAGE>   1


                                                                 EXHIBIT 10.7(A)

 THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), NOR UNDER THE SECURITIES LAWS OR "BLUE SKY" LAWS OF ANY
   STATE AND HAS NOT BEEN QUALIFIED UNDER THE TRUST INDENTURE ACT OF 1939, AS
   AMENDED. AS A RESULT, SUCH SECURITY MAY NOT BE SOLD OR TRANSFERRED EXCEPT
PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT AND ANY
APPLICABLE STATE SECURITIES OR "BLUE SKY" LAWS OR APPLICABLE EXEMPTIONS FROM THE
REGISTRATION REQUIREMENTS THEREOF. ANY SALE OR TRANSFER OF THIS SECURITY, OTHER
 THAN PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT, IS SUBJECT TO THE PRIOR
DELIVERY TO THE ISSUER OF AN OPINION OF COUNSEL REASONABLY SATISFACTORY IN FORM
   AND SUBSTANCE TO THE ISSUER THAT SUCH SALE OR TRANSFER IS EXEMPT FROM THE
    REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND ANY APPLICABLE STATE
                         SECURITIES OR "BLUE SKY" LAWS.


                         $7.0 MILLION SUBORDINATED NOTE


         INTERNATIONAL REMOTE IMAGING SYSTEMS, INC., a Delaware corporation (the
"COMPANY"), for value received, hereby promises to pay to DIGITAL IMAGING
TECHNOLOGIES, INC., a Delaware corporation ("DITI"), the principal sum of Seven
Million Dollars ($7,000,000), together with all accrued and unpaid interest, on
or before July 31, 2004 ("DUE DATE") as set forth in this Note. This
Subordinated Note (the "NOTE") is being issued in replacement of that certain 8
1/2% Senior Subordinated Note dated July 31, 1996 in the initial principal
amount of $7,000,000, and DITI is concurrently herewith surrendering such
subordinated note for cancellation.

         1.       Principal and Interest.

                  1.1 Principal. Subject to Section 4 (Subordination), the
Company shall pay $3,500,000 on or before June 29, 2001. The Company will pay
the remaining principal balance in thirty-six (36) monthly installments on the
first business day of each month beginning September 3, 2001 as follows: (a)
thirty-five (35) principal payments of $97,250 and (b) one final principal
payment of $96,250.

                  1.2 Interest Subject to Section 4 (Subordination), the Company
promises to pay interest in arrears on the unpaid principal amount of this Note
(a) on May 1, 2001 and July 31, 2001 at the rate of eight and one-half percent
(8 1/2%) per annum and (b) thereafter on the first business day of each calendar
month, commencing September 3, 2001, at the rate per annum equal to the
Reference Rate. The "REFERENCE RATE" shall be a variable interest rate and for
any particular calendar month shall be equal to the prime rate on first business
day of the such calendar month (as published in The Wall Street Journal) plus
two percent (2%). In the event that the Reference Rate changes for any
subsequent month, the applicable rate of interest hereunder shall automatically
increase or decrease accordingly, and the new rate shall be retroactive to the
first day of such month. Interest shall be computed on the basis of a 365-day
year. All past due principal and interest on this Note shall bear interest from
maturity of such principal or interest (in whatever manner same may be brought
about) at the lower of (i)

<PAGE>   2


the rate borne by this Note plus two percent (2%) per annum or (ii) the maximum
legal nonusurious rate of interest permitted by applicable law ("MAXIMUM RATE").

         2. Prepayment. Subject to Section 4 (Subordination), the Company may
prepay all or any part of the outstanding principal balance due under this Note
at any time without premium or penalty. All prepayments shall be applied first
against accrued but unpaid interest to the date of payment and the balance of
such payment shall be applied against the principal hereof.

         3. Method of Payment. Principal and interest are payable in lawful
money of the United States of America in immediately available funds to DITI at
its office located at 1900 St. James, Suite 700, Houston, Texas 77056 or at such
other address as designated in writing to the Company.

         4. Subordination. The payment of principal and interest on this Note is
subordinated in right of payment, to the extent and in the manner provided in
the Subordination Agreement, to the prior payment in full of all Obligations (as
defined therein) owed to Foothill Capital Corporation. The term "SUBORDINATION
AGREEMENT" means that certain Subordination Agreement dated as of March 14, 2001
between DITI and Foothill Capital Corporation.

         5. Default. Upon the occurrence of an Event of Default (as hereinafter
defined), DITI may declare the entirety of this Note, principal and interest, to
be immediately due and payable without any notice, and failure to exercise said
option shall not constitute a waiver on the part of DITI of the right to
exercise the same or any other remedy at any other time. Each of the following
conditions or events shall constitute an "EVENT OF DEFAULT":

                  (a) default by the Company in the payment of any installment
of principal when due hereunder or interest within five (5) days when due
hereunder;

                  (b) a decree or order by a court having jurisdiction in the
premises shall have been entered adjudging the Company a bankrupt or insolvent,
or approving as properly filed a petition seeking reorganization, readjustment,
arrangement, composition or similar relief for the Company under the federal
bankruptcy laws or any other similar applicable federal or state law, and such
decree or order shall have continued undischarged and unstayed for a period of
sixty (60) days; or a decree or order of a court having jurisdiction in the
premises for the appointment of a receiver or liquidator or trustee or assignee
in bankruptcy or insolvency of the Company or a substantial part of the property
of the Company, or for the winding up or liquidation of its affairs, shall have
been entered, and such decree or order shall have remained in force undischarged
and unstayed for a period of sixty (60) days; or any substantial part of the
property of the Company shall be sequestered or attached and shall not be
returned to the possession of the Company or released from such attachment
within sixty (60) days thereafter;

                  (c) the Company shall institute proceedings to be adjudicated
a voluntary bankrupt, or shall consent to the filing of a bankruptcy proceeding
against it, shall file a petition or answer or consent seeking reorganization,
readjustment, arrangement, composition or similar relief under the federal
bankruptcy laws, or any other similar applicable federal or state law, or shall
consent to the filing of any such petition, or shall consent to the appointment
of a receiver or liquidator or trustee or assignee in bankruptcy or insolvency
of it or of a substantial part of its property, or shall make an assignment for
the benefit of creditors, or shall admit in writing its inability to pay its
debts generally as they become due, or corporate action shall be taken by the
Company in furtherance of any of the aforesaid purposes; or


                                       2
<PAGE>   3


                  (d) default by the Company in the payment of principal of,
premium (if any) or interest on or any other payment of money due under, under
any obligation for borrowed money beyond any period of grace provided with
respect thereto, or in the performance of any other agreement, term or condition
contained in any agreement under which any such obligation is created if (i) the
principal amount of such obligation exceeds $500,000 and (ii) either (x) the
default involves the failure to pay principal when due or (y) the holder(s) of
such obligation (or a trustee on behalf of such holder or holders) accelerates
its stated maturity and such default is not waived or cured.

         6. Usury. It is the intention of the Company and DITI to conform
strictly to all applicable usury laws. It is therefore agreed that (i) in the
event that the maturity hereof is accelerated by reason of an election by DITI,
or if same is prepaid prior to maturity, all unearned interest shall be canceled
automatically or, if theretofore paid, shall either be refunded to the Company
or credited on the unpaid principal amount of this Note, whichever remedy is
chosen by DITI, (ii) the aggregate of all interest and other charges
constituting interest under applicable law and contracted for, chargeable or
receivable under this Note or otherwise in connection with the transaction for
which this Note is given shall never exceed the maximum amount of interest, nor
produce a rate in excess of the Maximum Rate, and (iii) if any excess interest
is provided for, it shall be deemed a mistake and the same shall either be
refunded to the Company or credited on the unpaid principal amount hereof and
this Note shall be automatically deemed reformed so as to permit only the
collection of the Maximum Rate and amount of interest. 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 to the full extent allowed by applicable law,
shall be amortized, prorated, allocated and spread through the full term of this
Note.

         7. Waivers. (a) Except as otherwise provided in this Note to the
contrary, the Company and each surety, endorser or guarantor, if any, waives
grace, notice, demand, presentment for payment, notice of nonpayment, protest,
notice of protest, notice of intention to accelerate, notice of acceleration of
the indebtedness due hereunder and all other notice, filing of suit and
diligence in collecting this Note, and the enforcing of any of the rights of
DITI, and consents and agrees that the time of payment hereof may be extended
without notice at any time and from time to time, and for periods of time
whether or not for a term or terms in excess of the original term hereof,
without notice or consideration to, or consent from the Company or any surety,
endorser or guarantor.

                  (b) With regard to any power, remedy or right provided herein
or otherwise available to any party hereunder, (i) no waiver or extension of
time will be effective unless expressly contained in a writing signed by the
waiving party or its representative, and (ii) no alteration, modification or
impairment will be implied by reason of any previous waiver, extension of time,
delay or omission in exercise or other indulgence.

         8. Cooperation. Each party hereto agrees to execute any and all further
documents and writings and to perform such other actions which may be or become
necessary or expedient to effectuate and carry out this Note.

         9. Successors and Assigns. This Note shall inure to the benefit of and
be binding upon the parties hereto and their respective successors and permitted
assigns. The Company may not assign this Note without the prior written consent
of DITI. DITI may not assign this Note except (i) to Ed Randall III, an
individual and stockholder of DITI, at any time or (ii) to any third party after
two years from the date hereof.


                                       3
<PAGE>   4


         10. Governing Law; Consent to Jurisdiction. Subject to Section 4
(Subordination), this Note shall be governed by, and construed and enforced in
accordance with, the laws of the State of Delaware without regard to the
conflict of laws rules of the State of Delaware or any other jurisdiction that
would call for the application of the laws of any jurisdiction other than the
State of Delaware. Each party hereto hereby irrevocably consents, for itself and
its legal representatives, partners, successors and assigns, to the exclusive
jurisdiction of the Courts of the State of Delaware for all purposes in
connection with any action or proceeding that arises from or relates to this
Note, and further agrees that any action arising from or relating to this
Agreement shall be instituted and prosecuted only in the courts of the State of
Delaware, and hereby waives any rights it may have to personal service of
summons, complaint, or other process in connection therewith, and agrees that
service may be made by registered or certified mail to such party at its
principal headquarters.

         11. Attorneys' Fees. DITI shall be entitled to recover any and all
attorneys' fees and court costs required to collect this Note.


                      *** [NEXT PAGE IS SIGNATURE PAGE] ***


                                       4
<PAGE>   5


                   Signature Page to Senior Subordinated Note

         IN WITNESS WHEREOF, the parties hereto have caused this Note to be duly
executed, as of March 14, 2001.


                                    "COMPANY"

                                    INTERNATIONAL REMOTE IMAGING
                                    SYSTEMS, INC., a Delaware corporation


                                    /s/ JOHN A. O'MALLEY
                                    --------------------------------------------
                                    John A. O'Malley
                                    Chairman, President and Chief Executive
                                    Officer


                                    "DITI"

                                    DIGITAL IMAGING TECHNOLOGIES, INC., a
                                    Delaware corporation


                                    /s/ TIMOTHY D. BURKETT
                                    --------------------------------------------
                                    Timothy D. Burkett
                                    Vice President