Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!dptspd!lcz
From: lcz@dptspd.sat.datapoint.com (Lee Ziegenhals)
Newsgroups: sci.electronics
Subject: Re: Phones used as intercoms
Message-ID: <757@dptspd.sat.datapoint.com>
Date: 21 Nov 90 15:29:35 GMT
References: <1990Nov12.181746.5465@syssoft.com> <4e1f9d95.18d2a@rako.UUCP>
Organization: Datapoint Corporation, San Antonio, TX
Lines: 20

rakoczynskij@rako.UUCP (Jurek Rakoczynski) writes:

>1. They have a 2 station intercom that goes between the phone and wall jack.
>   It provide a 'hold' function.  It probably uses the yel/blk leads of the
>   4 wire phone line that should tie all the phone jacks together (just a
>   guess on my part.  It probably won't work if you have the 'old' style
>   Princes phone that used a wall transformer to send power on the yel/blk
>   leads to light the buttons.). It's order # 43-206, price $49.94 in the 
>   1991 catalog.

The yel/blk wires are not needed.  Instead, they use a FM signal around
200 KHz or so (I forget the exact value) over the regular phone line (red/
grn pair).  It will work fine regardless of the use of the other pair.  I
have a set, and I'm quite pleased with them.  I used to have a set of
intercoms that worked the same way except over the power line.  However, they
would not talk well to my workshop, which is on a separate circuit from
the power pole.  I switched to the ones you mention, and they work great!

Lee Ziegenhals
(lcz@sat.datapoint.com)