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From: phil@amdcad.UUCP (Phil Ngai)
Newsgroups: net.dcom
Subject: Re: Office networking ala RS-232
Message-ID: <11620@amdcad.UUCP>
Date: Fri, 9-May-86 03:09:44 EDT
Article-I.D.: amdcad.11620
Posted: Fri May  9 03:09:44 1986
Date-Received: Sat, 10-May-86 04:01:59 EDT
References: <532@gould9.UUCP>
Reply-To: phil@amdcad.UUCP (Phil Ngai)
Distribution: na
Organization: AMD, Sunnyvale, California
Lines: 58
Keywords: patch panel, cabling

In article <532@gould9.UUCP> joel@gould9.UUCP (Joel West) writes:
>We're moving into new space and I'm tempted to wire up some of the
>offices (about 5) for RS232.  We currently have a lot of terminals,
>modems, phone lines and 1 micro, but a workstation or MicroVAX seems
>likely in the next year.
>
>First, how many wires would I need?  I was guessing 6 but a lot of
>the stuff I've seen suggests 8 (TD,RD RTS, CTS, DSR, SG, DCD,
>DTR) or 9 (add FG).  I guess that requires 10-conductor plenum.
>(INMAC, $.95/foot after 100 feet)

You can get by with 6 for terminals and modems (TD,RD,DTR,DCD,SG) with
the right adapters. I say 6 because we have used 6-wire telephone
cable, even though I only listed five signals.

We currently use 8-wire cable. This would allow us to run RTS/CTS for
"hardware" flow control someday. And there is a cheap adapter (WECO
258A) which breaks out a 25-pair cable to 6 8-wire outlets.  We like
the phone wire technology because it is dirt cheap due to massive
economies of scale yet engineered to last forever (well, 40 years).

To go from the phone wire to DB25 we use MOD-TAP adapters. They work
very well. Sometimes they work better than a 25-wire RS-232 cable.
(I have a nasty flame for one of our vendors which I won't post
here but would be happy to relate by mail.)

>Next, I need a source for a patch panel to hook up such a connection.  I've 
>found two sources for DB-25 panels (60-100 depending on the mounting), 
>then you have to populate it with DB-25 connectors.  Add to that 9-wire 
>patch cables (Inmac shielded, $19 ea quantity 5) and you have a few 
>hundred bucks.
>
>Even better was a patch panel based on 6- or 8-wire mini-modulars 
>and coiled patch cables.  But I can't find it in any of my catalogs 
>(Inmac, Dartek, Misco).

Indeed, MOD-TAP also makes patch panels based on 6 or 8-wire modulars.
We have tried them and they work quite well. You might want to
consider the use of phone company "punch blocks" (66M). We use them
for most of our terminals. Again, they are cheap ($5 terminates 100
wires) yet engineered to last forever. Also, they look complicated and
our users are too scared of them to change them behind our backs,
which we find desirable. In reality they are very very simple.

Note that ATT and DEC are starting to play with running RS232 over
phone cable. Their stuff probably works, but we've been using MOD-TAP
for a long time and see no reason to change.

Another option is to run Ethernet transceiver cable. You get 8 very
well shielded conductors and you can convert to Ethernet without
pulling new cable. It's a little more bulky and expensive but pulling
cable is usually the most expensive part anyway.
-- 
 If a reactor melts down in Russia will they call it the America syndrome?

 Phil Ngai +1 408 749 5720
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