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From: firstname.lastname@example.org (Allan Herriman)
Subject: Re: Telephone Ring Suppressor
Date: Sat, 21 Sep 2002 17:20:09 GMT
Organization: Agilent Technologies
NNTP-Posting-Date: Sat, 21 Sep 2002 17:20:04 +0000 (UTC)
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On Sat, 21 Sep 2002 14:45:51 GMT, George
>In article ,
> > Awhile back I posted an inquiry about a telephone ring
> > suppressor that could be switched in and out.
> > Rummaging through my junk pile looking for something
> > else I found it and snapped it apart... see photo on
> > alt.binaries.schematics.electronic
> > Message-ID:
> > It's nothing more than a full-wave rectifier that can be
> > switched in or out of the telephone circuit.
>I don't understand why this works. Also, is it possible to
>make an outgoing call if the ring suppressor is turned on?
>Well I guess it would be since most phones these days have a
>FWBR at the front end. But I still don't understand why it
>works to suppress ringing.
Ring detectors are usually (but not always!) capacitively coupled.
The capacitor may be 1uF or so (it varies from country to country and
from device to device - do a web search for "ringer equivalence
Without Jim's FWBR -> the AC ring signal gets coupled through the
series cap to the 'bell'.
With Jim's FWBR -> the series cap gets charged up, and no current
passes through the 'bell' after the first few cycles.
Note that the 'bell' typically includes its own FWBR, but there's a
big difference between AC coupling before and after a rectifier!
The outgoing call uses DC signalling, and isn't affected by the FWBR.
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