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                                                                   Exhibit 10.62
                                                                   -------------

                THIRD AMENDMENT TO CREDIT AND SECURITY AGREEMENT


     This Amendment, dated as of November 29, 2001, is made by and between RF
MONOLITHICS, INC., a Delaware corporation (the "Borrower"), and WELLS FARGO
BUSINESS CREDIT, INC., a Minnesota corporation (the "Lender").

                                    Recitals

     The Borrower and the Lender are parties to a Credit and Security Agreement
dated as of December 8, 2000, as amended by the First Amendment to Credit and
Security Agreement and Waiver of Defaults dated as of March 30, 2001, and the
Second Amendment to Credit and Security Agreement dated as of August 23, 2001
(as so amended, the "Credit Agreement"). Capitalized terms used in these
recitals have the meanings given to them in the Credit Agreement unless
otherwise specified.

     The Borrower has requested that certain amendments be made to the Credit
Agreement to be effective as of August 31, 2001 (the "Effective Date"), which
the Lender is willing to make pursuant to the terms and conditions set forth
herein.

     NOW, THEREFORE, in consideration of the premises and of the mutual
covenants and agreements herein contained, it is agreed as follows:

     1.   Defined Terms. Capitalized terms used in this Amendment which are
          -------------
defined in the Credit Agreement shall have the same meanings as defined therein,
unless otherwise defined herein. In addition, Section 1.1 of the Credit
Agreement is amended by amending the following definition:

          "Special Charges" means (i) certain restructuring charges of the
     Borrower to be taken during fiscal year ending August 31, 2001 including
     approximately (a) $1,000,000 for a fixed asset reserve, (b) $1,000,000 for
     an inventory reserve and (c) $200,000 of severance package accruals related
     to the plan for a reduction in work force, and (ii) a $7,049,000 write-off
     of deferred income tax benefits.

     2.   Amendment to Section 6.16. Section 6.16 of the Credit Agreement is
          -------------------------
amended in its entirety to read as follows:

          Minimum Book Net Worth. The Borrower will maintain, during each period
          ----------------------
     described below, its Book Net Worth in an amount not less than the amount
     set forth below:

          (a)  From June 1, 2001 through August 31, 2001, a minimum Book Net
     Worth of not less than $19,701,000; and

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          (b)  From September 1, 2001 through November 30, 2001, a minimum Book
     Net Worth of not less than the Book Net Worth as of FYE August 31, 2001,
     minus $700,000.

Notwithstanding the foregoing, if the Special Charges are not taken during the
fiscal year ending August 31, 2001, the covenants for the above-listed periods
will be adjusted to new levels to be determined by the Lender in its sole
discretion.

     3.   Amendment to Section 6.17. Section 6.17 of the Credit Agreement is
          -------------------------
amended in its entirety to read as follows:

          Quarterly Minimum Net Income. The Borrower will achieve (a) during the
          ----------------------------
     fiscal year ending on August 31, 2001, a minimum Net Income of greater than
     ($13,289,000); and (b) during the three month fiscal period from September
     1, 2001, to November 30, 2001, a minimum Net Income of greater than
     ($700,000). Notwithstanding the foregoing, if the Special Charges are not
     taken during the fiscal year ending August 31, 2001, the covenants for the
     above-listed periods will be adjusted to new levels to be determined by the
     Lender in its sole discretion.

     4.   Amendment to Section 6.18. Section 6.18 of the Credit Agreement is
          -------------------------
amended in its entirety to read as follows:

          Monthly Minimum Net Income. The Borrower will achieve, as of the end
          --------------------------
     of each month (a) during the fiscal year ended August 31, 2001, before the
     effectiveness of the Special Charges a minimum Net Income of greater than
     ($500,000); and (b) from September 1, 2001 through November 30, 2001, a
     minimum Net Income of greater than ($700,000).

     5.   Amendment to Exhibit C. Exhibit C to the Credit Agreement is hereby
          ----------------------
amended to be in the form of Exhibit C to this Amendment.

     6.   No Other Changes. Except as explicitly amended by this Amendment, all
          ----------------
of the terms and conditions of the Credit Agreement shall remain in full force
and effect and shall apply to any advance or letter of credit thereunder.

     7.   Conditions Precedent. This Amendment shall be effective as of the
          --------------------
Effective Date when the Lender shall have received an executed original hereof,
together with each of the following, each in substance and form acceptable to
the Lender in its sole discretion:

          (a)  The Acknowledgment and Agreement of Guarantor set forth at the
     end of this Amendment, duly executed by the Guarantor.

          (b)  A Certificate of the Secretary of the Borrower certifying as to
     (i) the resolutions of the board of directors of the Borrower approving the
     execution and delivery of this Amendment, (ii) the fact that the articles
     of incorporation and bylaws of the Borrower, which were certified and
     delivered to the Lender pursuant to the Certificate of Authority of the
     Borrower's secretary or assistant secretary dated as of December 8, 2000,
     continue in full force and effect and have not been amended or otherwise
     modified


                                       -2-

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     except as set forth in the Certificate to be delivered, and (iii)
     certifying that the officers and agents of the Borrower who have been
     certified to the Lender, pursuant to the Certificate of Authority of the
     Borrower's secretary or assistant secretary dated as of December 8, 2000,
     as being authorized to sign and to act on behalf of the Borrower continue
     to be so authorized or setting forth the sample signatures of each of the
     officers and agents of the Borrower authorized to execute and deliver this
     Amendment and all other documents, agreements and certificates on behalf of
     the Borrower.

          (c)  Such other matters as the Lender may require.

     8.   Representations and Warranties. The Borrower hereby represents and
          ------------------------------
warrants to the Lender as follows:

          (a)  The Borrower has all requisite power and authority to execute
     this Amendment and to perform all of its obligations hereunder, and this
     Amendment has been duly executed and delivered by the Borrower and
     constitutes the legal, valid and binding obligation of the Borrower,
     enforceable in accordance with its terms.

          (b)  The execution, delivery and performance by the Borrower of this
     Amendment have been duly authorized by all necessary corporate action and
     do not (i) require any authorization, consent or approval by any
     governmental department, commission, board, bureau, agency or
     instrumentality, domestic or foreign, (ii) violate any provision of any
     law, rule or regulation or of any order, writ, injunction or decree
     presently in effect, having applicability to the Borrower, or the articles
     of incorporation or by-laws of the Borrower, or (iii) result in a breach of
     or constitute a default under any indenture or loan or credit agreement or
     any other agreement, lease or instrument to which the Borrower is a party
     or by which it or its properties may be bound or affected.

          (c)  All of the representations and warranties contained in Article V
     of the Credit Agreement are correct on and as of the date hereof as though
     made on and as of such date, except to the extent that such representations
     and warranties relate solely to an earlier date.

     9.   References. All references in the Credit Agreement to "this Agreement"
          ----------
shall be deemed to refer to the Credit Agreement as amended hereby; and any and
all references in the Security Documents to the Credit Agreement shall be deemed
to refer to the Credit Agreement as amended hereby.

     10.  No Waiver. The execution of this Amendment and acceptance of any
          ---------
documents related hereto shall not be deemed to be a waiver of any Default or
Event of Default, breach or default under the Credit Agreement or breach,
default or event of default under any Security Document or other document held
by the Lender, whether or not known to the Lender and whether or not existing on
the date of this Amendment.

     11.  Release. THE BORROWER AND THE GUARANTOR BY SIGNING THE ACKNOWLEDGMENT
          -------
AND AGREEMENT OF GUARANTOR SET FORTH BELOW, EACH HEREBY ABSOLUTELY AND
UNCONDITIONALLY RELEASES AND FOREVER DISCHARGES THE LENDER, AND ANY AND ALL
PARTICIPANTS,


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PARENT CORPORATIONS, SUBSIDIARY CORPORATIONS, AFFILIATED CORPORATIONS, INSURERS,
INDEMNITORS, SUCCESSORS AND ASSIGNS THEREOF, TOGETHER WITH ALL OF THE PRESENT
AND FORMER DIRECTORS, OFFICERS, AGENTS AND EMPLOYEES OF ANY OF THE FOREGOING,
FROM ANY AND ALL CLAIMS, DEMANDS OR CAUSES OF ACTION OF ANY KIND, NATURE OR
DESCRIPTION, WHETHER ARISING IN LAW OR EQUITY OR UPON CONTRACT OR TORT OR UNDER
ANY STATE OR FEDERAL LAW OR OTHERWISE, WHICH THE BORROWER OR SUCH GUARANTOR HAS
HAD, NOW HAS OR HAS MADE CLAIM TO HAVE AGAINST ANY SUCH PERSON FOR OR BY REASON
OF ANY ACT, OMISSION, MATTER, CAUSE OR THING WHATSOEVER ARISING FROM THE
BEGINNING OF TIME TO AND INCLUDING THE DATE OF THIS AMENDMENT, WHETHER SUCH
CLAIMS, DEMANDS AND CAUSES OF ACTION ARE MATURED OR UNMATURED OR KNOWN OR
UNKNOWN.

     12.  Costs and Expenses. The Borrower hereby reaffirms its agreement under
          ------------------
the Credit Agreement to pay or reimburse the Lender on demand for all costs and
expenses incurred by the Lender in connection with the Loan Documents, including
without limitation all reasonable fees and disbursements of legal counsel.
Without limiting the generality of the foregoing, the Borrower specifically
agrees to pay all fees and disbursements of counsel to the Lender for the
services performed by such counsel in connection with the preparation of this
Amendment and the documents and instruments incidental hereto. The Borrower
hereby agrees that the Lender may, at any time or from time to time in its sole
discretion and without further authorization by the Borrower, make a loan to the
Borrower under the Credit Agreement, or apply the proceeds of any loan, for the
purpose of paying any such fees, disbursements, costs and expenses.

     13.  Miscellaneous. This Amendment and the Acknowledgment and Agreement of
          -------------
Guarantor may be executed in any number of counterparts, each of which when so
executed and delivered shall be deemed an original and all of which
counterparts, taken together, shall constitute one and the same instrument.

     14.  Governing Law; Jurisdiction, Venue; Waiver of Jury Trial. This
          --------------------------------------------------------
Amendment, the Acknowledgment and Agreement of Guarantor and the Loan Documents
shall be governed by and construed in accordance with the substantive laws
(other than conflict laws) of the State of Texas. Each party hereto and the
Guarantor hereby (i) consents to the personal jurisdiction of the state and
federal courts located in the State of Texas in connection with any controversy
related to this Amendment; (ii) waives any argument that venue in any such forum
is not convenient, (iii) agrees that any litigation initiated by the Lender or
the Borrower in connection with this Amendment or the other Loan Documents shall
be venued in either the District Court of Collin County, Texas, or the United
States District Court for the Northern District of Texas; and (iv) agrees that a
final judgment in any such suit, action or proceeding shall be conclusive and
may be enforced in other jurisdictions by suit on the judgment or in any other
manner provided by law. THE PARTIES WAIVE ANY RIGHT TO TRIAL BY JURY IN ANY
ACTION OR PROCEEDING BASED ON OR PERTAINING TO THIS AMENDMENT.

     15.  ENTIRE AGREEMENT. THIS AMENDMENT AND ALL OTHER INSTRUMENTS, DOCUMENTS
          ----------------
AND AGREEMENTS EXECUTED AND DELIVERED IN


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CONNECTION WITH THIS AMENDMENT EMBODY THE FINAL, ENTIRE AGREEMENT AMONG THE
PARTIES HERETO AND SUPERSEDE ANY AND ALL PRIOR COMMITMENTS, AGREEMENTS,
REPRESENTATIONS AND UNDERSTANDINGS, WHETHER WRITTEN OR ORAL, RELATING TO THIS
AMENDMENT, AND MAY NOT BE CONTRADICTED OR VARIED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OR DISCUSSIONS OF THE PARTIES
HERETO. THERE ARE NO ORAL AGREEMENTS AMONG THE PARTIES HERETO.

                            (Signature Page Follows)


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     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed as of the date first written above.


WELLS FARGO BUSINESS CREDIT, INC.              RF MONOLITHICS, INC.


By   /s/ Terrance O. McKinney                  By  /s/ David M. Kirk
    -------------------------------                -----------------------------
         Terrance O. McKinney                          David M. Kirk
         Assistant Vice President                      President