Date: Sun, 27 Sep 92 17:50:18 -0400
From: shri%unreal@cs.umass.edu
Newsgroups: comp.dcom.telecom
Subject: Re: Funny Phone Behaviour ... restatment of problem.
Organization: TELECOM Digest
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 12, Issue 741, Message 1 of 9

Hi,

  Just a day ago I had narrated my "funny phone problem" involving and
Easa-phone one one line and an answering machine on the other.

  Evidently I did not communicate correctly, (tho' I guess PAT did
understand me right, for otherwise he too would have thought this was
yet another "silly" wiring problem and punted to saving net-bandwidth
mode ;)

   Many thanks for the following replies ...

> From jartel!xenon!bongo!julian@nosc.mil: 

> You could have A lead problems. Check the answering machine and modem
> for A/A1 lead control switches.

> From elmo@netcom.com:

> 1) Check ... duplex adapter ... could be an "answering machine 
> disconnect".

> 2) Re-terminate your inside wiring.  I have had the same symptoms here
> in GTE due to intermittment opens in the loop caused by poor

No, that's not it.

 I am a "electroniker" myself, so I am quite sure that the duplexer in
each case is just a parallel of wires three and four (ring and tip).
In fact both duplexers parallel all four wires (A/A1 also) but I am
also sure that none of the devices in question use A/A1 in any way.

Also the wiring is not at fault, and it is a few dry capacitors in the
Easa-phone thats making the noise. This too I am sure.

 Guess I was not prespicous enough in my earlier post. Situation is ...

1. Line one (NXX-0661) has this Taiwanese phone + answering machine and
    a Sony cordless in parallel.

2. Line two (NXX-8484) has this old, cranky Panasonic Easa-phone
   and the archaic 300/1200 modem in parallel.

When I dial from Easa-phone into the University LAT servers, and
switch the modem into "Data" (I told you the modem was archaic :-),
the Easa-phone goes dead (low loop voltage due to additional load on
line two).  [In this line one is *not* involved].

When I call from the Easa-phone on line two into line one, all works
well if either the handset on the machine is picked or the Sony
cordless is picked up (note: both there on line one).

But if neither is picked, I hear side-tone (when I speak) and the
ring-back tone from the other end ... till the answering machine picks
up the call (note: on line one). Then my Easa-phone (note: on line two)
goes dead till the answering machine gives up and hangs up (note: on
line one) ... then the Easa-phone (note: on line two) comes alive again,
with side-tone when I speak.

Evidently what's on line two seems to affect my Easa-phone on line one
(which being finicky about line voltage is able to detect it ;.)

That's funny ... I though the SLICs in the exchange would isolate each
line, and in modern electronic switches only voice signal is switched
via PCM etc. and no DC connection is made between lines.

And, since it might probably help, both lines are on 413-549 exchange.

(I'll get hold of a voltmeter tomorrow and check my loop voltage for
different called parties and see if there is any correlation between
line two instrument and line one voltage.)


shrikumar ( shri@legato.cs.umass.edu, shri@iucaa.ernet.in )