Path: utzoo!utgpu!attcan!uunet!husc6!think!ames!amdahl!rtech!hoptoad!pozar
From: pozar@hoptoad.uucp (Tim Pozar)
Newsgroups: sci.electronics
Subject: Re: crossing phone lines
Message-ID: <5472@hoptoad.uucp>
Date: 27 Sep 88 13:00:31 GMT
References: <7921@cit-vax.Caltech.Edu> <2689@kitty.UUCP> <657@eplunix.UUCP>
Organization: Syncstream/Widget Systems (San Francisco)
Lines: 27

raoul@eplunix.UUCP (Otero) wrote:
> In article <2689@kitty.UUCP>, larry@kitty.UUCP (Larry Lippman) writes:
> > 	In the on-hook (i.e., idle) state, connecting the two lines exactly
> > in parallel (tip1-to-tip2 and ring1-to-ring2) will, in general, be undetected
> > by the central office apparatus since there will be no current flow.
> 
> No such luck. Unless the voltage matching is perfect, which it never is,
> a small DC current will flow from one line to the other. This will 
> mess up both your lines, and you will not be able to use either. Ma
> Bell will also usually disconnect the lines within about a week of this
> sort of nonsense, thinking there is a short somewhere (there is!).
> 
> However, don't take any of our word for it. Just short them together
> at the phone jack and see.... Try some real scientific method.

    Or the way I've always done it was via a transformer...

	t1 -----    ----- t2
		)||(
    600 ohms	)||(    600 ohms
		)||(
        r1 -----    ----- r2
-- 
 ...sun!hoptoad!\                                     Tim Pozar
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