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Path: utzoo!watmath!wateng!joe
From: joe@wateng.UUCP (Joe Morrison)
Newsgroups: net.dcom,net.periphs
Subject: building a modem - How do I use the telephone lines?
Message-ID: <2371@wateng.UUCP>
Date: Fri, 10-May-85 14:52:27 EDT
Article-I.D.: wateng.2371
Posted: Fri May 10 14:52:27 1985
Date-Received: Sat, 11-May-85 01:29:59 EDT
Reply-To: joe@wateng.UUCP (Joe Morrison)
Organization: U of Waterloo, Ontario
Lines: 23
Xref: watmath net.dcom:974 net.periphs:750

I am trying to build a 300 baud direct connect modem around the TMS99532
(from TI) and I need to know how to interface to the telephone lines. I
have several articles on *accoustically* coupled modems, but I can't
find anything on direct coupled ones.

Questions - the jack that plugs into the wall has four coloured wires
coming out of it -- what do the four colours mean? What happens when
the phone rings? Does the voltage on one of the wires go high or something?
How can you tell if the phone is off the hook? Any ideas on how to 
actually interface the TMS99532 to the phone lines? I'm told I need
to use an isolation transformer...

Any information on any of the above things would be greatly appreciated!
If I get lots of replies that don't conflict with each other (:-), I will
post the info to the net.

Thanks in advance! - joe
-- 
Joe Morrison,  University of Waterloo, Ontario, Canada

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