Path: utzoo!dciem!nrcaer!scs!spl1!laidbak!att!pacbell!ames!husc6!bloom-beacon!westmark.UUCP!dave
From: dave@westmark.UUCP (Dave Levenson)
Newsgroups: comp.dcom.telecom
Subject: Re: Three wire lines
Message-ID: <197@westmark.UUCP>
Date: 4 Jun 88 03:57:17 GMT
Article-I.D.: westmark.197
References: <8806011249.AA04333@NADC.ARPA>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: Westmark, Inc., Warren, NJ, USA
Lines: 33
Approved: telecom@xx.lcs.mit.edu


In article <8806011249.AA04333@NADC.ARPA>, prindle@NADC.ARPA (Frank Prindle) writes:
> if a customer willingly wants to do away with it; the LOC will gladly switch
> you to private service, but you are on your own to rewire (or toss) the phones.
> 


Actually, when the CO applies ringing between tip and ground, it
also applies ground to the ring side of the loop, thus applying a
dead short accross the ringer that is not supposed to be ringing. 
Similarly, the tip side is grounded when the `ring party' is being
alerted.  A useful by-product of this is that a standard phone wired
for `bridged ringing' will ring correctly when either the tip party
or the ring party is rung on a two-party line.

If your phone is arranged for ring party ringing, it will work
correctly with private line bridged ringing, as the tip side of the
line is normally at ground potential anyway.

My local telephone book (from NJ Bell) indicates that customers with
two-party lines are not provided modular jacks, and may not purchase
their own telephone instruments!  This exception to the usual
equipment rules results from the opportunity for toll-fraud that
results when the tip party's phone is not wired for tip party
identification.  NJ Bell also states that two-party is a `closed
service' which means that existing customers may keep it, but no new
two-party service is offered.

-- 
Dave Levenson
Westmark, Inc.		The Man in the Mooney
Warren, NJ USA
{rutgers | clyde | mtune | ihnp4}!westmark!dave