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From: bet@mcnc.org@ecsvax.UUCP
Newsgroups: mod.telecom
Subject: Re: Wiring diagram for 25-pair plugs
Message-ID: <8701221520.AA11923@ecsvax>
Date: Thu, 22-Jan-87 10:20:39 EST
Article-I.D.: ecsvax.8701221520.AA11923
Posted: Thu Jan 22 10:20:39 1987
Date-Received: Thu, 29-Jan-87 04:40:48 EST
References: <8701210657.AA19208@ucbvax.Berkeley.EDU>
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: ecsvax.uucp!bet@mcnc.org (Bennett E. Todd III)
Organization: Duke User Services
Lines: 23
Approved: telecom@xx.lcs.mit.edu


I don't know about the actual pin layout of those connectors, but I have
hooked up a modem to one. Graybar makes a box called a Supertap
(undoubtedly there are others) that brings out the first 4 lines of a
key system to modular jacks; to work in such a hookup the modem must
support A-A1 signalling (short two additional pins, called A and A1, to
assert the line -- this gets the dialtone and lights up the in-use
lights on everybody elses phones). I know the standard Hayes Smartmodem
1200 external modem can be switched to assert A-A1; that's what I
installed. If the lines are in a rotary (a set of lines all answering
the same incoming number) it makes sense to try to hook up the modem to
the *last* line in the rotary; it is the line most likely to be free. No
matter how you hook the sucker in other people will be able to disrupt
the modem conversation by picking up that line while it is in use; this
is the nature of key systems. It is always much better to try to get a
separate line.

-Bennett
-- 
Bennett Todd -- Duke Computation Center, Durham, NC 27706-7756; (919) 684-3695
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