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From: chris@yarra.oz.au (Chris Jankowski)
Newsgroups: comp.dcom.lans
Subject: Re: RS232 cable
Message-ID: <66561@yarra.oz.au>
Date: 30 Oct 90 05:30:58 GMT
References: <2404@gould.doc.ic.ac.uk>
Organization: Pyramid Technology Corp PL, Melb., Australia
Lines: 30

In article <2404@gould.doc.ic.ac.uk> epl@doc.ic.ac.uk (Edward Peter Lennon) writes:
> 2-Where did I get the figure of 50 foot maximum distance for RS 232 
>communications from.

From the standard as published in 1969. It guarantees that it would work
on this length of cable up to maximum frequency specified by the standard
(which is 19,200 bits/s if I remember correctly) in high level of EMI,
on a crappy unshielded, ribbon cable and with your senders using low voltage
sources eg. 3.5 or 5V.

If you use 12 or 15V or perhaps 25V (still within the spec) sources, 
shielded twisted pair cable you can have it working on lengths >1,000m, 
but formally it is outside the spec.

We can be a little more adventurous these days knowing that 10BaseT allows us
to run 10Mbit/s on unshielded twisted pair for up to ~50m (~165 feet or so).
(:-)).

Hope this helps.

Caution:
All figures above are from the top of my head and may be slightly off the mark.

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