Hi ROBERT.

26-Jan-03 09:58:00, ROBERT SAYRE wrote to ROY J. TELLASON


 TW>> Actualy becasue of the Length Limits on serial communications
 TW>> cables didn't most of those old nets use Current Loops?

 RJT>> Not that I'm aware of.


 RJT>> There really isn't that much of a length limitation on serial
 RJT>> lines,  it depends on a few things,  mostly whether or not
 RJT>> you're running shielded wi and most importantly,  at what baud
 RJT>> rate you want to run.  The above-menti printer ran at 300 baud,
 RJT>> which was fine because it was rated at 30 cps an so a faster
 RJT>> rate wouldn't have made anything better.  I know that when yo up
 RJT>> around 9600 and higher speeds cabling gets more critical and
 RJT>> allowable length gets way shorter.

 RS> If you go RS-485 you can go thousands of feet at 9600 baud. We're
 RS> doing it.

IIRC RS-485 is a balanced system, like current loop, so yeah long
distances are practical.

Another balanced system has been used for runs of many miles - telephone :)

MIDI is also balanced, but AFAIK most midi line driver circuits arent up to
driving the signals long distances.

 RS> TTYL.

 RS> Robert

 RS> * SLMR 2.1a * Pure drivel drives ordinary drivel off the TV
 RS> screen.


 -=> Bye <=-

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