Path: utzoo!attcan!uunet!wuarchive!texbell!vector!telecom-gateway
From: kitty!larry@uunet.uu.net (Larry Lippman)
Newsgroups: comp.dcom.telecom
Subject: Special Information Tones
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Date: 27 Sep 89 03:29:11 GMT
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In article  carroll1!dtroup@uunet.uu.
net (Dave Troup) writes:
>	Does anyone know what the recording alert tones are? You know-those
>	dee-doo-DOO, "The number you have reached..." What are the frequencies
>	to them.  Ive NEVER been able to find out what those are.

	These tones are called SIT (Special Information Tones).  Their
purpose is to permit an automatic Call Disposition Analyzer (CDA) to
differentiate between a human voice and a recorded announcement, and
to categorize the type of recorded announcement.

	A Call Disposition Analyzer is an automatic device, today totally
computer-controlled, which automatically dials test calls over certain
test subscriber lines, tandem trunks and intertoll trunks for the purpose
of evaluating the connectivity and grade of service of all or a portion of
the DDD network.  A CDA may access a local subscriber line and outpulse
using DP or DTMF, or in the case of tandem or intertoll trunks outpulse
using MF.  A CDA may be programmed to dial a milliwatt test line (102-type
from tandem or intertoll) or a transmission/noise measurement ATMS responder
test line (105-type from tandem or intertoll).  The results of test calls
are logged and categorized.  The SIT tones facilitate categorizing a call
failure which results in a recording.

	I don't know the SIT frequencies, either, except that they are not
far from 600 Hz.  The two CDA's which I have seen (Northeast Electronics
and WECO) did not in fact have any frequency discrimination circuitry;
they merely looked for three sequential tones occurring in less than
3 seconds using a bandpass filter centered around 600 Hz.

	Actually, I believe that AT&T had some more grandiose plans for
the SIT tones which in fact were not implemented.  Last I knew - which
is actually some years ago - the same department at AT&T which assigned
the verbal tandem and intertoll announcement failure codes for recordings
said stay tuned for SIT assignments.  I stayed tuned for a while, but
never heard anything. :-)

<> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
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