[comp.dcom.modems] 60 Hz hum on Zmodem 2400

levene@eniac.seas.upenn.edu (Robert A. Levene) (05/12/89)

I recently replaced my Bell dataphone (as in an earlier article) with
an ATD 2400 Baud modem, a "Zuckerchip" ZModem V.22 bis.  It seems to
work except for one quirk:

When software cuts off the speaker, I still hear faint 60Hz hum!  The
same thing happened in another modem in the store.  Also, when
characters appear, there is a faint noise.  My brute-force fix is to
install a switch to the speaker. (So help me, I'm an EE.) That cuts
off the hum, but doesn't explain this quirk.

Has anyone heard this effect on their inexpensive modems?
  (No flames about not buying a $400 Hayes, please)

Thanks,
-- Rob
--
Robert A. Levene,    EE '89    Moore School of Electrical Engineering
levene@eniac.seas.upenn.edu    University of Pennsylvania, Philadelphia  PA

"... Soon we'll be out amid the cold world's strife,
     Soon we'll be sliding down the razor blade of life."  -- Tom Lehrer