old modems & a packet switcher

From: Allison J Parent <allisonp_at_world.std.com>
Date: Mon Aug 3 14:35:15 1998

< I'm surprised by this. I'd thought about ways of linking any number
< of old PCs at up to 2000 foot distances, and thought about recreating a

2000ft is within the capability of RS422 at data rates that are in the
megabit range. There are other simple solutions like RS423 at low data
rates. The DEC mill used to have many central systems that often were
remote from the users by as many as 6 floors vertically and several
hundred feet horizontally. (Royalt was ML11/M1 and our group was
ML3-6/A1) we still ran 4800 or 9600 serial over the 500+ feet of wire
of the standard dual twisted pairs of phone co wire.

The biggest problem was the possibility of ground loops. With care
that's can be avoided though RS422 (balanced differential) can deal with
that as can RS485.

Allison
Received on Mon Aug 03 1998 - 14:35:15 BST

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