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                                    EXHIBIT C

                                POWER OF ATTORNEY


KNOW ALL MEN BY THESE PRESENT,  that the  undersigned,  Winston  Partners II LDC
(the "Company"),  a Cayman Islands exempted  limited  duration  company,  hereby
makes,  constitutes  and appoints  PETER A. HURWITZ as the  Company's  agent and
attorney-in-fact  for the purpose of  executing  on behalf of the  Company,  all
documents,  certificates,   instruments,   statements,  filings  and  agreements
("documents")  to be  filed  with  or  delivered  to  any  foreign  or  domestic
governmental  or regulatory body or required or requested by any other person or
entity  pursuant  to  any  legal  or  regulatory  requirement  relating  to  the
acquisition,  ownership,  management  or  disposition  of  securities  or  other
investments,  and any other documents relating or ancillary  thereto,  including
but not limited to, all  documents  relating to filings  with the United  States
Securities and Exchange Commission (the "SEC") pursuant to the Securities Act of
1933 or the  Securities  Exchange  Act of 1934  (the  "Act")  and the  rules and
regulations promulgated thereunder, including: (1) all documents relating to the
beneficial ownership of securities required to be filed with the SEC pursuant to
Section 13(d) or Section 16(a) of the Act including, without limitation: (a) any
acquisition  statements  on  Schedule  13D or  Schedule  13G and any  amendments
thereto, (b) any joint filing agreements pursuant to Rule 13d-1(f),  and (c) any
initial  statements  of, or  statements of changes in,  beneficial  ownership of
securities  on Form 3, Form 4 or Form 5 and (2) any  information  statements  on
Form 13F required to be filed with the SEC pursuant to Section 13(f) of the Act.
All past acts of the attorney-in-fact in furtherance of the foregoing are hereby
ratified and confirmed.

         This  power  of  attorney  shall be valid  from the date  hereof  until
revoked by the Company.

         IN WITNESS  WHEREOF,  I have executed this  instrument this 25th day of
October, 1996.


         WINSTON PARTNERS II LDC



         By:      /s/ Kieran Conroy   /s/ Wiekert Weber
                  -------------------------------------
                  Name:  Kieran Conroy / Wiekert Weber