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From: firstname.lastname@example.org (Allan Herriman)
Subject: Re: Telephone Ring Suppressor
Date: Tue, 24 Sep 2002 05:29:11 GMT
Organization: Agilent Technologies
References: <email@example.com> <3D8FCA72.DB9DB70C@sympatico.ca>
NNTP-Posting-Date: Tue, 24 Sep 2002 05:29:13 +0000 (UTC)
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On Mon, 23 Sep 2002 19:14:10 -0700, Gerry Schneider
>Allan Herriman wrote:
>> On Sat, 21 Sep 2002 14:45:51 GMT, George
>> >In article ,
>> >Jim-T@analog_innovations.com says...
>> > > 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.
>ALWAYS in N. America. See FCC part 68.
Here's an example of a ring detector in a DAA that is DC coupled. It
works by sensing the peak voltage:
According to the web site, this DAA has been specifically designed for
North American operation.
It needs the addition of an RC network to model a ringer, so that the
exchange can tell that there's a "phone" on the other end of the line.
But this is just a dummy ringer. The real ring detector is DC coupled
(and very high impedance).
>> 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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