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From: goldstein@carafe.enet.dec.com (Fred R. Goldstein)
Newsgroups: comp.dcom.telecom
Subject: Re: A Few ISDN Questions
Message-ID: <4527@accuvax.nwu.edu>
Date: 28 Feb 90 17:06:51 GMT
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X-Telecom-Digest: Volume 10, Issue 133, Message 1 of 10


In article <4459@accuvax.nwu.edu>, casbs@csli.stanford.edu (Lynn Gale) 
writes...
 
>Is it known at this point in time what medium ISDN will run on?  In
>particular, what number of wire pairs are necessary and do they need
>to be shielded or unshielded?  (Thinking about wiring decisions with
>the future in mind...)

The ISDN Basic Rate ("2B+D") interface at Reference Point U (Network
Interface, in the US) is 2-wires, copper.  At Reference Points S and T
(intended for inside wiring), it's 4-wire copper.  The two pairs are
send and receive (balanced).  Unshielded twisted pair is all you need.
NOT quad, and no need to use fancy shielded wire.

The Primary Rate Interface ("23B+D") is based on good old fashioned T1
(North America/Japan) and E1 (rest of Earth).  That runs on two
twisted pairs too.

>Will ISDN incorporate Fax functions?  RS-232?  What else besides
>voice?

ISDN ships bits.  It allows the bits to be handled raw (64 kbps
circuit switched, and some multiples of that), or as X.25 packets, or
as digitized voice (A-law and mu-law, with conversion as appropriate).
FAX may be supported over the 64 kbps service, for which Group 4 was
designed, although Group 3 can also use it.  RS-232 is a physical
layer not part of ISDN, though you can certainly have a Terminal
Adapter (ISDNese for "modem function") that has RS-232 on one side and
ISDN on the other.  Essentially you can do with the 64 kbps as your
imagination allows.  


Fred R. Goldstein
goldstein@carafe.enet.dec.com
                 or goldstein@delni.enet.dec.com
                    voice:  +1 508 486 7388