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From: dbb@aicchi.UUCP
Newsgroups: comp.dcom.telecom
Subject: Re: 3-tone no connection question
Message-ID: <953@aicchi.UUCP>
Date: Fri, 22-May-87 10:15:12 EDT
Article-I.D.: aicchi.953
Posted: Fri May 22 10:15:12 1987
Date-Received: Sun, 24-May-87 04:48:39 EDT
References: <3075@well.UUCP>
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: umix!itivax!chinet!aicchi!dbb (Burch)
Distribution: world
Organization: Analysts International Corp; Chicago Branch
Lines: 19
Keywords: SIT, Answering Machines, Toll system
Approved: telecom@buit1.bu.edu
Summary: SIT are used only internal to the toll system.



Well, those three tones, (Which used to be real loud, 0dB), are
called SIT or Special Information Tones.  They are used to help
your local phone switch when you are connected to an intercept
recorder.  They tell your switch what to do about billing your
call.  However, once offhook supervision has been returned by the
party you call, they have no effect.  Therefore, you may use them
on your answering machine and they will have no effect. Except 
Cuteness...  Seriously, I doubt that a recorder could send those
with enough purity to be heard by the PLL's that listen for them.


-- 
-David B. (Ben) Burch
 Analysts International Corp.
 Chicago Branch (ihnp4!aicchi!dbb)

"Argue for your limitations, and they are yours." - R. Bach