Document:

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                                                                  EXHIBIT 10.4.6

              TRANCHE A NOTE AND TRANCHE B NOTE EXTENSION AGREEMENT

      This Tranche A Note and Tranche B Note Extension Agreement (this
"Agreement") dated as of April ___, 2001 is entered into by and between CRL
Systems, Inc., a Nevada corporation ("Borrower") and Harman Acquisition Corp.
(f/k/a/ Orban, Inc.), a Delaware corporation ("Lender").

                                    RECITALS

      A.    The parties hereto entered into a Credit Agreement dated May 31,
2000 (the "Credit Agreement");

      B.    Pursuant to Section 2.1 of the Credit Agreement, Borrower agreed to
pay $250,000 of the principal amount of the Tranche A Note to Lender on March
31, 2001, June 30, 2001, September 30, 2001, December 31, 2001 and March 31,
2002 (the "Quarterly Payments");

      C.    Pursuant to Section 2.2 of the Credit Agreement, Borrower agreed to
pay the full principal amount of the Tranche B Note to Lender on September 30,
2000 (the "Tranche B Maturity Date");

      D.    The parties hereto entered into a Tranche A Note Extension
Agreement, dated March 30, 2001 (the "Tranche A. Extension Agreement"), pursuant
to which the payment of the March 2001 Obligation was extended to July 31, 2001;

      E.    The parties hereto executed a First Extension Agreement, a Second
Extension Agreement, a Third Extension Agreement and a Fourth Extension
Agreement, dated February 22, 2001 (collectively, the "Tranche B Extension
Agreements") pursuant to which Lender extended the Tranche B Maturity Date to
May 14, 2001; and

      F.    Lender wishes, subject to the conditions set forth in this
Agreement, to (i) defer the payment of the Quarterly Payment, including the
March 2001 Obligation, to April 30, 2002, and (ii) further extend the Tranche B
Maturity Date to April 30, 2002.

      NOW THEREFORE, IN CONSIDERATION of the mutual covenants and agreements
contained in this Agreement and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties to this
Agreement hereby agree as follows:

                                    AGREEMENT

      1.    Lender hereby defers the payment of the Quarterly Payments to April
30, 2002, unless such payment shall otherwise become payable sooner as provided
in the Loan Documents; provided, however that on or before September 30, 2001,
Borrower shall pay $250,000 to Lender in satisfaction of the September 30, 2001
payment required to be paid by Borrower to Lender in accordance with Section 2.1
of the Credit Agreement.
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      2.    Lender hereby extends the Tranche B Maturity Date to April 30, 2002.

      3.    Borrower acknowledges that failure of Borrower to fulfill any of its
obligations under this Agreement shall be deemed an Event of Default under the
Credit Agreement.

      4.    Borrower and Circuit Research Labs, Inc. (the "Company") agree that
the Obligations are valid and enforceable obligations of Borrower and hereby
confirm, acknowledges and ratifies the existence of the Obligations and
Borrower's obligations to Lender with respect thereto as set forth in the Credit
Agreement, and all other obligations of Borrower and the Company to Lender under
the Loan Documents.

      5.    Borrower represents and warrants to Lender as follows:

            a     The Borrower is a corporation duly organized, validly existing
and in good standing under the laws of the jurisdiction indicated at the
beginning of this Agreement.

            b     The execution, delivery and performance by the Borrower of
this Agreement are within the Borrower's corporate powers, have been duly
authorized by all necessary corporate action and do not violate, contravene or
create a breach, violation or default under (i) the Borrower's charter or
by-laws, (ii) any Requirement of Law or any Contractual Obligation binding on or
affecting the Borrower, or result in, or require, the creation or imposition of
any mortgage, deed of trust, pledge, Lien, security interest or other charge,
encumbrance or preferential arrangement of any nature (other than as
contemplated by the Loan Documents) upon or with respect to any of the
properties now owned or hereafter acquired by the Borrower.

            c     No authorization, approval or other action by, and no notice
to or filing with, any Governmental Authority is required for the due execution,
delivery and performance by the Borrower of this Agreement.

            d     There is no pending or threatened action or proceeding
affecting the Borrower or any of its Subsidiaries before any court, Governmental
Authority or arbitrator, which could materially and adversely affect the
financial condition or operations of the Borrower or any Subsidiary or which
purports to affect the legality, validity or enforceability of this Agreement.

      6.    THIS AGREEMENT, THE TRANCHE A EXTENSION AGREEMENT, THE TRANCHE B
EXTENSION AGREEMENTS, AND THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT
OF THE BORROWER AND THE LENDER WITH RESPECT TO THE SUBJECT MATTER HEREOF, AND
THERE ARE NO PROMISES, UNDERTAKINGS, REPRESENTATIONS OR WARRANTIES BY THE LENDER
RELATIVE TO THE SUBJECT MATTER HEREOF NOT EXPRESSLY SET FORTH OR REFERRED TO
HEREIN OR IN THE OTHER LOAN DOCUMENTS, THE TRANCHE A EXTENSION AGREEMENT OR THE
TRANCHE B EXTENSION AGREEMENTS.

      7.    Except for the extension specifically contained herein, the terms,
conditions and obligations contained in the Loan Documents, the Tranche A
Extension Agreement and the Tranche B Extension Agreements remain in full force
and effect and are hereby ratified and
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confirmed. The execution, delivery and effectiveness of this Agreement will not,
operate as a waiver of any right, power or remedy of Lender under any of the
Loan Documents, the Tranche A Extension Agreement or the Tranche B Extension
Agreements nor constitute a waiver of any provision of any of the Loan
Documents, the Tranche A Extension Agreement or the Tranche B Extension
Agreements.

      8.    This Agreement will be deemed to be a contract made under the Laws
of the State of New York and for all purposes will be governed by and
interpreted in accordance with the laws prevailing in the State of New York,
without regard to principles of conflict of laws.

      9.    This Agreement may be executed in several counterparts each of which
when so executed will be deemed to be an original and all of which will together
constitute one and the same agreement. This Agreement will become effective when
this Agreement is executed by each of the parties hereto.

      10.   Capitalized terms used but not defined in this Agreement have the
meanings ascribed to them in the Credit Agreement, the Tranche A Extension
Agreement and the Tranche B Extension Agreements.
<PAGE>
      IN WITNESS WHEREOF, Borrower and Harman Acquisition Corp. have executed
this Agreement as of the first date written above.

                                    CRL SYSTEMS, INC.

                                    By:
                                         ---------------------------------------
                                    Name:
                                           -------------------------------------
                                    Title:
                                            ------------------------------------

                                    HARMAN ACQUISITION CORP.

                                    By:  /s/ Frank Meredith
                                         ---------------------------------------
                                    Name:  Frank Meredith
                                           -------------------------------------
                                    Title:  Chief Financial Officer
                                            ------------------------------------

Agreed to and accepted by

CIRCUIT RESEARCH LABS, INC.

By:
     ----------------------------------
Name:
       --------------------------------
Title:
        -------------------------------MORGAN STANLEY SELECT EQUITY TRUST
            MORGAN STANLEY HIGH-TECHNOLOGY 35 INDEX PORTFOLIO 2002-1

                            REFERENCE TRUST AGREEMENT

     This  Reference  Trust  Agreement  dated            ,  2001 between  MORGAN
STANLEY DW INC., as Depositor,  and The Bank of New York, as Trustee, sets forth
certain provisions in full and incorporates other provisions by reference to the
document  entitled  "Dean  Witter  Select  Equity  Trust,  Trust  Indenture  and
Agreement" (the "Basic Agreement") dated September 30,  1993. Such provisions as
are incorporated by reference constitute a single instrument (the "Indenture").

                                WITNESSETH THAT:

     In  consideration  of the  premises  and of the  mutual  agreements  herein
contained, the Depositor and the Trustee agree as follows:

                                       I.

                     STANDARD TERMS AND CONDITIONS OF TRUST

     Subject to the provisions of Part II hereof,  all the provisions  contained
in the Basic  Agreement are herein  incorporated  by reference in their entirety
and  shall be deemed  to be a part of this  instrument  as fully and to the same
extent as though said  provisions had been set forth in full in this  instrument
except that the Basic Agreement is hereby amended as follows:

          A. The first  sentence of Section 2.01 is amended to add the following
     language at the end of such  sentence:  "and/or cash (or a letter of credit
     in lieu of cash) with  instructions  to the Trustee to purchase one or more
     of such  Securities  which  cash  (or cash in an  amount  equal to the face
     amount of the letter of  credit),  to the extent not used by the Trustee to
     purchase  such  Securities  within the 90-day  period  following  the first
     deposit of Securities in the Trust, shall be distributed to Unit Holders on
     the  Distribution  Date next  following  such 90-day period or such earlier
     date as the Depositor and the Trustee determine".

          B. The first  sentence of Section 2.06 is amended to add the following
     language after "Securities"))": "and/or cash (or a letter of credit in lieu

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     of  cash)  with  instructions  to the  Trustee  to  purchase  one  or  more
     Additional  Securities  which cash (or cash in an amount  equal to the face
     amount of the letter of  credit),  to the extent not used by the Trustee to
     purchase such Additional  Securities within the 90-day period following the
     first  deposit of  Securities in the Trust,  shall be  distributed  to Unit
     Holders on the Distribution  Date next following such 90-day period or such
     earlier date as the Depositor and the Trustee determine".

          C.  Article  III,  entitled  "Administration  of Trust",  Section 3.01
     Initial Cost shall be amended as follows:

               (i) the first part of the first  sentence of Section 3.01 Initial
          Cost shall be amended to substitute the following  language before the
          phrase "provided, however":

                    "With  respect  to the Trust,  the cost of the  preparation,
               printing   and   execution   of  the   Certificates,   Indenture,
               Registration Statement and other documents relating to the Trust,
               Federal and State  registration  fees and costs, the initial fees
               and  expenses of the  Trustee,  legal and  auditing  expenses and
               other out-of-pocket  organizational  expenses,  to the extent not
               borne by the Sponsor, shall be paid by the Trust;"

          D. The third  paragraph of Section  3.05 is hereby  amended to add the
     following sentence after the first sentence thereof:  "Depositor may direct
     the Trustee to invest the proceeds of any sale of  Securities  not required
     for the redemption of Units in eligible money market  instruments  selected
     by the Depositor which will include only negotiable certificates of deposit
     or time deposits of domestic banks which are members of the Federal Deposit
     Insurance  Corporation  and which  have,  together  with their  branches or
     subsidiaries,   more  than  $2  billion  in  total   assets,   except  that
     certificates  of deposit or time deposits of smaller  domestic banks may be
     held  provided  the deposit does not exceed the  insurance  coverage on the
     instrument  (which  currently is $100,000),  and provided  further that the
     Trust's  aggregate  holding of  certificates  of  deposit or time  deposits
     issued  by the  Trustee  may not  exceed  the  insurance  coverage  of such
     obligations and U.S. Treasury notes or bills (which shall be held until the
     maturity  thereof)  each of which  matures prior to the earlier of the next

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     following Distribution Date or 90 days after receipt, the principal thereof
     and interest  thereon (to the extent such interest is not used to pay Trust
     expenses) to be distributed on the earlier of the 90th day after receipt or
     the next following Distribution Date."

          E. The  first  sentence  of each of  Sections  3.10,  3.11 and 3.12 is
     amended to insert the following language at the beginning of such sentence,
     "Except as otherwise provided in Section 3.13,".

          F. The following new Section 3.13 is added:

          Section 3.13.  Extraordinary Event - Security Retention and Voting. In
     the event the  Trustee is notified of any action to be taken or proposed to
     be taken by holders of the securities  held by the Trust in connection with
     any proposed merger, reorganization, spin-off, split-off or split-up by the
     issuer of stock or  securities  held in the Trust,  the Trustee  shall take
     such action or refrain  from taking any action,  as  appropriate,  so as to
     insure  that the  securities  are voted as closely as  possible in the same
     manner and in the same general  proportion  as are the  securities  held by
     owners  other than the Trust.  If stock or  securities  are received by the
     Trustee,  with or without cash, as a result of any merger,  reorganization,
     spin-off,  split-off or split-up by the issuer of stock or securities  held
     in the Trust, the Trustee at the direction of the Depositor may retain such
     stock or  securities  in the Trust.  Neither the  Depositor nor the Trustee
     shall be liable to any person for any action or failure to take action with
     respect to this section.

          G.  Section  1.01 is  amended  to add the  following  definition:  (9)
     "Deferred  Sales  Charge" shall mean any deferred  sales charge  payable in
     accordance with the provisions of Section 3.12 hereof,  as set forth in the
     prospectus for a Trust.  Definitions following this definition (9) shall be
     renumbered.

          H. Section 3.05 is hereby amended to add the following paragraph after
     the end thereof:  On each Deferred  Sales Charge  payment date set forth in
     the  prospectus  for a Trust,  the Trustee  shall pay the  account  created
     pursuant to Section 3.12 the amount of the Deferred Sales Charge payable on
     each such date as stated in the prospectus  for a Trust.  Such amount shall

<PAGE>

     be withdrawn from the Principal Account from the amounts therein designated
     for such purpose.

          I. Section 3.06B(3) shall be amended by adding the following: "and any
     Deferred Sales Charge paid".

          J.  Section  3.08 shall be amended by adding the  following at the end
     thereof: "In order to pay the Deferred Sales Charge, the Trustee shall sell
     or liquidate an amount of Securities at such time and from time to time and
     in such manner as the Depositor shall direct such that the proceeds of such
     sale or  liquidation  shall  equal the  amount  required  to be paid to the
     Depositor pursuant to the Deferred Sales Charge program as set forth in the
     prospectus for a Trust.

          K. Section 3.12 shall be added as follows:

          Section 3.12.  Deferred  Sales Charge.  If the  prospectus for a Trust
     specifies  a  Deferred  Sales  Charge,  the  Trustee  shall,  on the  dates
     specified in and as permitted by the  prospectus,  withdraw from the Income
     Account if such account is  designated  in the  prospectus as the source of
     the payments of the Deferred  Sales Charge,  or to the extent funds are not
     available in that account or if such account is not so designated, from the
     Principal  Account,  an amount per Unit  specified  in the  prospectus  and
     credit  such  amount to a  special,  non-Trust  account  maintained  at the
     Trustee out of which the Deferred  Sales Charge will be  distributed to the
     Depositor.  If the Income  Account is not  designated  as the source of the
     Deferred  Sales  Charge  payment  or if  the  balances  in the  Income  and
     Principal  Accounts  are  insufficient  to make  any such  withdrawal,  the
     Trustee shall,  as directed by the Depositor,  either advance funds,  if so
     agreed to by the Trustee, in an amount equal to the proposed withdrawal and
     be entitled to reimbursement of such advance upon the deposit of additional
     monies in the Income Account or the Principal Account,  sell Securities and
     credit the proceeds thereof to such special  Depositor's  account or credit
     Securities in kind to such special  Depositor's  Account.  Such  directions
     shall  identify the  Securities,  if any, to be sold or distributed in kind
     and shall  contain,  if the Trustee is directed by the  Depositor to sell a
     Security,  instructions  as to  execution  of such sales.  If a Unit Holder
     redeems  Units prior to full  payment of the  Deferred  Sales  Charge,  the
     Trustee shall,  if so provided in the prospectus,  on the Redemption  Date,
     withhold  from the  Redemption  Price payment to such Unit Holder an amount

<PAGE>

     equal to the unpaid  portion of the Deferred  Sales  Charge and  distribute
     such amount to such special  Depositor's account or, if the Depositor shall
     purchase  such Unit  pursuant  to the terms of  Section  5.02  hereof,  the
     Depositor  shall pay the  Redemption  Price  for such Unit less the  unpaid
     portion  of the  Deferred  Sales  Charge.  The  Depositor  may at any  time
     instruct the Trustee to  distribute  to the  Depositor  cash or  Securities
     previously credited to the special Depositor's account.

          L.  Reference to "Morgan  Stanley Dean Witter  Select Equity Trust" is
     replaced by "Morgan Stanley Select Equity Trust".

          M.  Reference  to "Dean Witter  Reynolds  Inc." is replaced by "Morgan
     Stanley DW Inc."

          N.  Section  2.03 is  amended to add the  following  to the end of the
     first  paragraph  thereof.  The number of Units may be increased  through a
     split of the  Units or  decreased  through  a  reverse  split  thereof,  as
     directed by the Depositor,  which revised number of Units shall be recorded
     by Trustee on its books.

                                       II.

                      SPECIAL TERMS AND CONDITIONS OF TRUST

     The following special terms and conditions are hereby agreed to:

          A. The Trust is denominated  Morgan Stanley Select Equity Trust Morgan
     Stanley High-Technology 35 Index Portfolio 2002-1 (the "High-Tech Trust").

          B. The publicly  traded  stocks  listed in Schedule A hereto are those
     which,  subject  to the  terms of this  Indenture,  have  been or are to be
     deposited in trust under this Indenture.

          C. The term, "Depositor" shall mean Morgan Stanley DW Inc.

          D. The aggregate number of Units referred to in Sections 2.03 and 9.01
     of the Basic Agreement is         for the High-Tech Trust.

<PAGE>

          E. A  Unit  is  hereby  declared  initially  equal  to 1/         th
     for  the High-Tech Trust.

          F. The term "In-Kind Distribution Date" shall mean        ,          .

          G. The term  "Record  Dates" shall mean       ,         ,         ,
             ,           ,         and        ,           and such other date as
     the Depositor may direct.

          H. The term  "Distribution  Dates  shall  mean ,           ,         ,
                   ,          ,           and           ,        and such other
     date as the Depositor may direct.

          I. The term "Termination Date" shall mean       ,       .

          J. The Depositor's Annual Portfolio Supervision Fee shall be a maximum
     of $0.25 per 100 Units.

          K.  The  Trustee's  Annual  Fee as  defined  in  Section  6.04  of the
     Indenture shall be $   per 100 Units.

          L. For a Unit Holder to receive "in-kind" distribution during the life
     of the Trust other than in  connection  with a  rollover,  such Unit Holder
     must tender at least 25,000 Units for redemption. On the In-Kind Date there
     is no minimum  amount of Units that a Unit  Holder  must tender in order to
     receive an "in-kind" distribution.

          M. The  Indenture is amended to provide  that the period  during which
     the  Trustee  shall  liquidate  the Trust  Securities  shall not  exceed 14
     business days  commencing  on the first  business day following the In-Kind
     Date.

               (Signatures and acknowledgments on separate pages)

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