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From: dave@westmark.westmark.com (Dave Levenson)
Newsgroups: comp.dcom.telecom
Subject: Re: Touch-Tone Specifications
Message-ID: <72182@bu.edu.bu.edu>
Date: 13 Jan 91 02:35:27 GMT
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In article <16015@accuvax.nwu.edu>, hpa@casbah.acns.nwu.edu (Peter
Anvin) writes:

> Also, in Sweden the indoor wiring is serial, not parallel, meaning
> that if you lift the handset on one phone, you disconnect all phones
> with lower priority, i.e. further away from the incoming line.  This
> looks to me like it almost has to be some form of on/off relay here?

It sounds to me as though that's what the second pair is for.  If the
telephone sets are wired in series, then each set would require two
pairs from the wall-socket: Tip and Ring in, and Tip and Ring out to
the next set on the line.  The switchhook in each set probably
implements a 'double-pole, double-throw' arrangement.  The inbound
pair is connected to the outbound pair when the instrument is on-hook.
When the set is off-hook, this connection is broken, and the inbound
pair is connected to the hybrid in the set.

This is a wild guess on my part; I have never been in Sweden, and have
no knowlege of the telephone system there.


Dave Levenson		Internet: dave@westmark.com
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