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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: sci.electronics
Subject: Re: Phone systems
Message-ID: <7805@utzoo.UUCP>
Date: Fri, 20-Mar-87 13:20:29 EST
Article-I.D.: utzoo.7805
Posted: Fri Mar 20 13:20:29 1987
Date-Received: Fri, 20-Mar-87 13:20:29 EST
References: <1443@ncr-sd.SanDiego.NCR.COM> <642@oliveb.UUCP>, <2281@tektools.TEK.COM>
Organization: U of Toronto Zoology
Lines: 23

> If both phones are on the *same* CO, is it possible to have a box that
> will display the phone number of the calling party?  Can this only be
> done with the cooperation of the phone company, or is there some
> device I can connect to my end of the phone line?

Variants of this question come up in mod.telecom with some regularity.
The general answer is "no".  To find out the number of the calling party,
the phone system needs to tell your phone what it is.  The phone system
does not normally do this.  There is no standard electronic way to ask
for it.  Old exchanges cannot do it at all.  Modern phone exchanges are
increasingly capable of doing various interesting things like this, but
as I recall, this particular service isn't available except perhaps on a
few experimental exchanges.  (I speak here of the general phone system,
not of the peculiar things that may be possible within private exchanges
serving a single organization.)

Even once the hardware is capable of it, I'd think it very likely that you
will have to explicitly ask for it and pay for it.  The phone system is
under considerable pressure to keep the "basic service" charges low, which
means making as much money as possible on non-basic services.
-- 
"We must choose: the stars or	Henry Spencer @ U of Toronto Zoology
the dust.  Which shall it be?"	{allegra,ihnp4,decvax,pyramid}!utzoo!henry