Document:

<PAGE>

                                                                     EXHIBIT 4.2

                                 PROMISSORY NOTE

Date:  September 30, 2002

Maker:  RETRACTABLE TECHNOLOGIES, INC.

Maker's Mailing Address (including county):  511 Lobo Lane, Little Elm, Denton
                                             County, Texas  75065

Payee: KATIE PETROLEUM, INC.

Place for Payment (including county):  10325 Gaywood, Dallas, Dallas County,
                                         Texas 75229-6608

Principal Amount:  Three Million and NO/100 Dollars ($3,000,000.00)

Annual Interest Rate on Unpaid Principal from Date: 1% over "Prime Rate" as
shown in the Money Rates column of the Wall Street Journal, redetermined on the
first business day of each calendar month.

Annual Interest Rate on Matured, Unpaid Amounts:  Same as Annual Interest Rate

Terms of Payment (principal and interest): Interest only payable monthly
commencing on November 1, 2002 and on the first day of each calendar month
thereafter until February 1, 2004. Commencing on March 1, 2004 and on the first
day of each calendar month thereafter Maker shall make payments of principal and
interest (being equal payments as possible taking into consideration changes in
interest rates during the term of this Note) so that this Note will be fully
paid, principal and interest, on September 30, 2012.

         This Promissory Note is subject to the terms and conditions of that
certain Loan Agreement of even date herewith between Maker and Payee.

         Maker promises to pay to the order of Payee at the place for payment
and according to the terms of payment the principal amount plus interest at the
rates stated above. All unpaid amounts shall be due by the final scheduled
payment date.

         If Maker defaults in the payment of this note or in the performance of
any obligation in any instrument collateral to it, and the default continues
after Payee gives Maker notice of the default and the time within which it must
be cured, as may be required by law or by written agreement, then Payee may
declare the unpaid principal balance and earned interest on this note
immediately due. Maker and Guarantor waive demands for payment, presentations
for payment, notices of intention to accelerate maturity, notices of
acceleration of maturity, protests, and notices of protest, to the extent
permitted by law.

         This payment of all sums due under this Promissory Note is secured by
the personal guaranty of THOMAS J. SHAW.

         If this Promissory Note or any instrument collateral to it is given to
an attorney for collection or enforcement, or if suit is brought for collection
or enforcement, or if it is collected or enforced through bankruptcy, or other
judicial proceeding, then Maker shall pay Payee all costs of collection and
enforcement, including reasonable attorney's fees and court costs, in addition
to other amounts due.

         Interest on the debt evidenced by this note shall not exceed the
maximum amount of nonusurious interest that may be contracted for, taken,
reserved, charged, or received under law; any interest in excess of that maximum
amount shall be credited on the principal of the debt or, if that has been paid,
refunded. On any acceleration or required or permitted prepayment, any such
excess shall be canceled automatically as of the acceleration or prepayment or,
if already paid, credited on the principal of the debt or, if the principal of
the debt has been paid, refunded. This provision overrides other provisions in
this and all other

<PAGE>

instruments concerning the debt.

         The Maker is responsible for all obligations represented by this
note.

KATIE PETROLEUM, INC.                    RETRACTABLE TECHNOLOGIES, INC.

By:        /s/ John A. Jackson           By:        /s/ Thomas J. Shaw
   ------------------------------            -----------------------------------
           President                                     President
Payee                                    Maker

                                                   /s/ Thomas J. Shaw
                                         ---------------------------------------
                                                       Thomas J. Shaw
                                        Guarantor

PREPARED IN THE LAW OFFICE OF: Lionel E. Gilly<PAGE>

                                  Exhibit 10.1

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Matrix Service Company, Inc. (the
"Company") on form 10-Q for the period ended August 31, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I Bradley
S. Vetal, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C.
(S)1350, as adopted pursuant to (S)906 of the Sarbanes-Oxley Act of 2002, that
based on my knowledge:

     1.   The Report fully complies with the requirements of section 13(a) or
          15(d) of the Securities Exchange Act of 1934; and

     2.   The information contained in the Report fairly presents, in all
          material respects, the financial condition and result of operations of
          the Company.

This certification is deemed to accompany this Quarterly Report on Form 10-Q,
but is not deemed "filed" for purpose of Section 18 of the Securities Exchange
Act of 1934, as amended, or otherwise.

/s/ Bradley S. Vetal

Bradley S. Vetal
Chief Executive Officer
October 10, 2002<PAGE>

                                  Exhibit 10.2

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Matrix Service Company, Inc. (the
"Company") on form 10-Q for the period ended August 31, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I Bradley
S. Vetal, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C.
(S)1350, as adopted pursuant to (S)906 of the Sarbanes-Oxley Act of 2002, that
based on my knowledge:

     3.   The Report fully complies with the requirements of section 13(a) or
          15(d) of the Securities Exchange Act of 1934; and

     4.   The information contained in the Report fairly presents, in all
          material respects, the financial condition and result of operations of
          the Company.

This certification is deemed to accompany this Quarterly Report on Form 10-Q,
but is not deemed "filed" for purpose of Section 18 of the Securities Exchange
Act of 1934, as amended, or otherwise.

/s/ Michael J. Hall

Michael J. Hall
Vice President - Financial
And Chief Financial Officer
October 10, 2002<PAGE>

                                   EXHIBIT 4.1

                             TRIO-TECH INTERNATIONAL
                   REDEEMABLE WARRANT TO PURCHASE COMMON STOCK

         This certifies that _________________________________ is entitled at
any time up to and including 5:00 p.m. California Time on the date 36 months
following the date of the Final Closing (the "Expiration Date") to purchase from
Trio-Tech International, a California corporation (hereinafter called the
"Company), fully paid and nonassessable shares of Common Stock of the Company at
a price ("Exercise Price") of Seven Dollars ($7.00) per share upon the surrender
hereof to the Company at its office at 355 Parkside Drive, San Fernando,
California 91340, during its usual business hours of any business day, with
simultaneous payment therefor in lawful money of the United States of the
purchase price set forth above.

         This Warrant is one of a series of substantially identical warrants
(the "Warrants") that are being sold and issued as part of Units (the "Units")
consisting of Common Stock and Warrants of the Company in a private placement
offering (the "Offering") being made by Paragon Capital Corporation, as
Placement Agent.

         Exercise of Warrant. Subject to the terms and conditions hereof, this
Warrant may be exercised in whole or in part, at any time during normal business
hours prior to the Expiration Date, by (i) delivery of a written notice, in the
form of the Notice of Exercise attached hereto, of such holder's election to
exercise this Warrant, which notice shall specify the number of shares to be
purchased upon exercise hereof, (ii) payment to the Company of an amount equal
to the Exercise Price multiplied by the number of shares as to which this
Warrant is being exercised (plus any applicable issue or transfer taxes) in cash
or by bank check, and (iii) the surrender of this Warrant at the principal
office of the Company. If this Warrant is being exercised only in part, the
Company shall issue a new Warrant identical in all respects to this Warrant
except that it shall represent the right to purchase the number of shares as to
which this Warrant is not then being exercised. The Company has the right at its
sole discretion to extend the Expiration Date by notice given to all Warrant
holders. No fractional share shall be issued upon the exercise of rights to
purchase hereunder.

         Antidilution Adjustment. If the number of outstanding shares of capital
stock of the Company are increased or decreased by a stock split, reverse stock
split, stock dividend, stock combination, recapitalization or the like, the
Exercise Price and the number of shares purchasable pursuant to this Warrant
shall be adjusted proportionately so that the ratio of (i) the aggregate number
of shares purchasable by exercise of this Warrant to (ii) the total number of
shares outstanding immediately following such stock split, reverse stock split,
stock dividend, stock combination, recapitalization or the like shall remain
unchanged, and the aggregate purchase price of shares issuable pursuant to this
Warrant shall remain unchanged. No adjustment shall be made for any issuances of
shares other than as described above.

         Registration of Underlying Common Stock. Prior to the Company giving a
notice of redemption of Warrants hereunder, the Company must file a Registration
Statement with the Securities and Exchange Commission ("SEC") to register, under
the Securities Act of 1933, as amended (the "Securities Act"), the resale of the
Common Stock issuable upon exercise of this Warrant and all other Warrants, and
such Registration Statement must have become effective. The Company shall
maintain the effectiveness thereof until all shares registered thereunder have
been

                                       1.

<PAGE>

disposed of or are freely tradeable under Rule 144(k) under the Securities Act.

         Redemption of Warrants. The Company may call the Warrants for
redemption in whole or in part at a price of $.10 for each share issuable upon
exercise of the Warrants, by written notice specifying the redemption date, such
notice to be mailed at least 30 days before such redemption date, to the Warrant
holders at their respective addresses as they appear on the books of the
Company; provided, however, that such notice may only be mailed within 10 days
following any period of 20 consecutive trading days during which the closing bid
price for the Common Stock on the Nasdaq Small Cap Market (or such other trading
market as the Common Stock may then be trading) has equalled or exceeded $9.00
per share on each such day (subject to adjustment for any stock dividends, stock
splits, reverse stock splits or similar events that shall have occurred between
the date of issuance of this Warrant and the date of such notice). If the
Company elects to redeem part, but not all, of the Warrants, then such
redemption shall be made pro rata with respect to all of the Warrants. This
Warrant may be exercised at any time prior to the close of business on the date
prior to the redemption date, and if not then exercised will terminate and be
cancelled.

         Restrictions on Transfer of Warrants. Until such time as the resale of
the Common Stock issuable upon exercise of this Warrant has become registered
under the Securities Act, this Warrant may not be sold or transferred to any
Person except to other Persons who are registered owners of the Warrants. The
term "Person" means an individual or a corporation, partnership, trust, limited
liability company, incorporated or unincorporated association, joint venture, or
other entity of any kind.

         Notice of Adjustment of Exercise Price and Number of Warrant Shares.
Upon any adjustment of the Exercise Price of this Warrant or the number of
shares issuable hereunder, the Company shall give notice thereof to the
registered holder of this Warrant which shall set forth the new Exercise Price
in effect after such adjustment and the increase or decrease, if any, in the
number of shares issuable upon exercise of this Warrant. All such notices shall
set forth in reasonable detail the method of calculation and the facts upon
which such calculation is based.

         Notice of Certain Events. In case at any time (a) there shall be any
reorganization or reclassification of the capital stock of the Company or
consolidation or merger of the Company with, or sale of all or substantially all
of its assets to, another corporation or entity; or (b) there shall be a
voluntary or involuntary dissolution, liquidation or winding up of the Company;
then, in any one or more of said cases, the Company shall give notice to the
registered holder of this Warrant of the date on which such reorganization,
reclassification, consolidation, merger, sale, dissolution, liquidation or
winding up shall take place. Such notice shall be given not less than 20 days
prior to the action in question.

         No Rights as Shareholder. Prior to the exercise of this Warrant the
holder of this Warrant shall not be entitled to any rights of a shareholder of
the Company, including, without limitation, the right to vote, to receive
dividends or other distributions, or to receive notice of meetings of
shareholders.

         Lost, Stolen, Mutilated or Destroyed Warrants. If this Warrant is lost,
stolen, mutilated or destroyed, the Company shall, on such terms as to indemnity
or otherwise as it may in its discretion impose (which in the case of a
mutilated Warrant shall include the surrender thereof), issue a new Warrant of
like denomination and tenor as the Warrant so lost, stolen, mutilated or
destroyed. Any such new Warrant shall constitute an original contractual
obligation of the Company, whether or not the allegedly lost, stolen, mutilated
or destroyed Warrant shall be at any time enforceable by anyone.

         Miscellaneous. This Warrant and any term hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the Person
or holder hereof against which

                                       2.

<PAGE>

enforcement of such change, waiver, discharge or termination is sought. The
headings in this Warrant are for purposes of reference only and shall not limit
or otherwise affect the meaning hereof.

         IN WITNESS WHEREOF, the Company has executed this Warrant as of the day
and year first above written.

Dated:  __________________                   TRIO-TECH INTERNATIONAL

                                             By_________________________________
                                                  A. Charles Wilson, Chairman

                                       3.

<PAGE>

                               NOTICE OF EXERCISE

                     TO BE EXECUTED BY THE REGISTERED HOLDER
                        IN ORDER TO EXERCISE THIS WARRANT

                             TRIO-TECH INTERNATIONAL

         The undersigned hereby exercises the right to purchase
_____________________________ shares of Common Stock covered by this Warrant
according to the conditions thereof and herewith makes payment of
$______________________________, the aggregate Exercise Price of such shares of
Common Stock.

                                        [Print or type name(s) of Holder. If
                                        Holder is a trust, partnership,
                                        corporation or other entity, print name
                                        and title of authorized signatory.]

                                        Signature(s) of Holder or authorized
                                        signatory

                                       4.

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00043-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00043-of-00352.parquet"}], [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00043-of-00352.parquet"}], [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00043-of-00352.parquet"}]]