Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!gem.mps.ohio-state.edu!apple!sun-barr!texsun!texbell!vector!telecom-gateway
From: dritchey@ihlpb.att.com (Donald L Ritchey)
Newsgroups: comp.dcom.telecom
Subject: Re: Wrong Numbers With Nobody Talking
Message-ID: 
Date: 22 Sep 89 18:25:47 GMT
Sender: news@vector.Dallas.TX.US
Lines: 41
Approved: telecom-request@vector.dallas.tx.us
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@vector.dallas.tx.us
X-TELECOM-Digest: volume 9, issue 397, message 5 of 7

Summary:

well!slf@lll-crg.llnl.gov (Sharon Lynne Fisher):
In article (Message-ID:  ), you wrote
> X-TELECOM-Digest: volume 9, issue 393, message 3 of 11

> I moved a couple of months back, and I've had a weird problem since then.  I
> get lots of wrong numbers.  Some of them are the normal "Is Joe there?" and
> I say no and the person goes away.  But the vast majority of them have no
> voice at all.  I pick up the phone, hear a faint 'clickclickclick' in the
> background, and nothing happens, so I hang up.  On my answering machine,
> I don't get any message either; just those faint sounds.  I thought perhaps
> it was people calling me from a computer, but then I'd hear a modem tone,
> wouldn't I?  Incidentally, I get these calls both long-distance and local.
> Anybody have any idea what's going on?

Originating modems do not emit tones on connection.  Terminating (or
answering) modems answer the call with one of a variety of tones to
indicate the type of modem and its desired speed of connection (300,
1200, 2400, or other).  The clicking you hear in the earpiece is
probably the modem switching its various filters in and out of circuit
to determine what type of modem it is connected to.  Try whistling a
low, continuous tone into the mouthpiece (and varying the frequency you
whistle) and see if you get the other end to start its transmission
speed negotiation preamble (that will definitely identify the other end
as a modem).  I have used that trick to see if connections I was trying
to debug were getting through to a modem, when I couldn't bridge a
speaker or butt set onto the line.

I don't design or work with modems other than as a user, so I may be
wrong on the explanations of the clicking.  I can speak from experience
about the originating modems not generating tones, unless some of the
newer, fancier modems that have come into use in the last few years do
things differently.


Don Ritchey       dritchey@cbnewsc.att.com
(or in real life) dritchey@ihlpb.att.com
AT&T Bell Labs IH 1D-409
Naperville, IL 60566
(312) 979-6179