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From: kitty!larry@uunet.uu.net (Larry Lippman)
Newsgroups: comp.dcom.telecom
Subject: Modification of Ringback Tone by Subscriber Apparatus
Message-ID: <telecom11.401.3@eecs.nwu.edu>
Date: 27 May 91 04:33:46 GMT
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X-Telecom-Digest: Volume 11, Issue 401, Message 3 of 10

In article <telecom11.397.6@eecs.nwu.edu> YSAR1111@vm1.yorku.ca (Rick
Broadhead) writes:

> I had a similar experience just a few days ago.  I dialed a number in
> my own area code (416), exchange 392, and was quite surprised to hear
> a double ring.  This is the first time I have ever heard a double
> ring on the calling end.

	Is it possible that you encountered a "line extender" for FAX
and/or modem use, which *immediately* trips the central office ringing
and supplies its own ringing signal?  Under these circumstances, you
may never get a chance to hear the CO ringback tone, with the
resultant ringback tone being solely the product of the subscriber's
line extender.

> [Moderator's Note: I don't know if you meant it the way it came out,
> but the telephone instrument has *nothing* to do with the ring you
> hear as the caller.  What you heard must have been some kind of fluke;
> some temporary switch problem.   PAT]

	The above explanation about a line extender notwitstanding, it
*is* possible to hear a ringback tone modification cased by the
subscriber instrument.  In electromechanical CO's, such as SxS, XY and
some No. 1 XBAR (if any is still left), ringback tone is usually
supplied by capacitive coupling between the called subscriber line
while it is being rung and the calling party side of the connector or
intraoffice trunk.  Some older telephones having electronic ringers
may create audible signals on the telephone line due to the design of
the ringer oscillator circuit.  While such audible signals cannot
modify the cadence of the ringback signal, they can provide a decided
modification to its sound as heard by the calling party.

	I first noticed the above many years ago in an Ericophone
(remember those?) having a electronic tone ringer.


Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
VOICE: 716/688-1231       {boulder, rutgers, watmath}!ub!kitty!larry
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