*** Portions of this exhibit are considered  confidential  by the registrant and
have been omitted from this filing and filed  separately with the Securities and
Exchange Commission pursuant to a request for confidential treatment.


                               FIRST AMENDMENT TO
                          CREDIT AND GUARANTY AGREEMENT

      First Amendment (this "AMENDMENT") dated as of November 19, 2001 to Credit
and Guaranty Agreement (the "AGREEMENT") dated as of May 31, 2001 among GN Great
Nordic A/S as Lender ("LENDER"),  Sonus-USA,  Inc. as Borrower  ("BORROWER") and
Sonus Corp.  as Guarantor  ("GUARANTOR";  together,  Borrower and  Guarantor are
collectively, the "OBLIGORS").

                          WITNESSETH:

      WHEREAS,  the Lender and the  Obligors  desire to amend the  Agreement  as
provided herein.

      NOW, THEREFORE, the parties hereto agree as follows:

      SECTION 1. Defined Terms.  (a)  Capitalized  terms used but not defined in
this Amendment have the meanings set forth in the Agreement.

      (b)  Section  1.01 of the  Agreement  is  hereby  amended  by  adding  the
following new defined term in the appropriate alphabetical order:

            "FIRST  AMENDMENT"  means the First Amendment to Credit and Guaranty
      Agreement dated as of November 19, 2001 among the Lender, the Borrower and
      Sonus Corp.

      SECTION 2.  Amendment to the  definition of EBITDA.  (a) The definition of
"EBITDA"  contained  in Section  1.01 of the  Agreement  is hereby  amended  and
restated in its entirety to read as follows:

      "EBITDA" means, for any period, the consolidated net income of Sonus Corp.
      and its  consolidated  subsidiaries  for such period,  plus, to the extent
      deducted  in  determining   consolidated   net  income  for  such  period,
      depreciation,  interest,  amortization  and income  taxes,  determined  in
      accordance with GAAP  eliminating  (i) all  intercompany  items,  (ii) all
      earnings  attributable  to  equity  interests  in  Persons  that  are  not
      consolidated  subsidiaries unless actually received in cash by Sonus Corp.
      or  a  consolidated   subsidiary,   (iii)  all  income  arising  from  the
      forgiveness,  adjustment,  or negotiated  settlement of any  indebtedness,
      (iv) any  extraordinary  items of income or expense  (including  gains and
      losses from asset sales),  (v) any increase or decrease in income  arising
      from any change in Sonus Corp.'s method of  accounting,  (vi) any interest
      income and (vii) for any period  including  any quarter  ended  during the
      fiscal year ended July 31, 2001, any items of income or expense  contained
      in  Schedule  I to the First  Amendment  to the  extent  such  items  were
      recorded in such quarter.

                                      -1-
<PAGE>


      SECTION 3.  Effectiveness.  This  Amendment  shall be effective as soon as
counterparts  hereof  have been  executed  and  delivered  by the Lender and the
Obligors.

      SECTION 4. Effect of Amendment.  Except as amended  hereby,  the Agreement
shall  remain  unchanged  and  effective as of May 31,  2001.  The  Agreement as
amended hereby shall continue in full force and effect.

      SECTION  5.  Governing  Law.  This  Amendment  shall  be  governed  by and
construed in accordance with the laws of the State of New York.

      SECTION  6.  Counterparts.  This  Amendment  may be  executed  in  several
counterparts  with the same  effect  as if the  parties  executing  the  several
counterparts had all executed one counterpart.


                                      -2-
<PAGE>


      IN WITNESS  WHEREOF,  the parties  have caused this  Amendment  to be duly
executed by their  respective  authorized  officers as of the day and year first
written above.

                                    SONUS-USA, INC., as
                                    Borrower


                                    By: /s/ Mark Richards
                                        --------------------------
                                        Name: Mark Richards
                                        Title: Chief Financial Officer


                                    SONUS CORP., as Guarantor


                                    By: /s/ Mark Richards
                                        --------------------------
                                        Name: Mark Richards
                                        Title: Chief Financial Officer


                                    GN GREAT NORDIC A/S, as Lender


                                    By: /s/ Jens Oue Olsen
                                        --------------------------
                                        Name:Jens Oue Olsen
                                        Title: Chief Financial Officer and
                                               Executive Vice President

                                   GN GREAT NORDIC A/S, as Lender


                                   By: /s/ Jirn Kildegaard
                                       ---------------------------
                                       Name: Jirn Kildegaard
                                       Title: Chief Executive Officer and
                                              President

                                      -3-
<PAGE>


                                   SCHEDULE I
                                       TO
                FIRST AMENDMENT TO CREDIT AND GUARANTY AGREEMENT

    ELIMINATIONS FOR THE PURPOSE OF CLAUSE (VII) OF THE DEFINITION OF EBITDA

Product Revenue:
***                                                 173,516

Network Revenue:
***                                                 203,089
***                                                 440,251
Accrue ***% commission for GN                        87,564
Accrue ***                                          103,100
                                                    -------
                                                    834,004
                                                    =======

Cost of Sales One Time Adjustments:
***                                                  58,954
***                                                 190,302
Accrue for portion of differences between
  ***                                               617,360
                                                    -------
                                                    866,616
                                                    =======

Corp G & A - Personnel
Accrue for severance and relocation                 199,333
                                                    =======

Corp G & A - Other
***                                               3,630,000
***                                                 160,400
                                                    -------
                                                  3,790,400
                                                  =========

Other:
Write off Goodwill of 7 clinics                      55,000
                                                  =========


                                                  5,918,869

***  Confidential  portions  omitted  pursuant  to a  request  for  confidential
treatment