21 Jun
2005
21 Jun
'05
4:14 p.m.
But you normally don't want to connect frame
grounds
(pin 1 on RS-232 cables iirc). You sometimes get an
amazing amount of current through the cables, even
enough to melt them.
In a lot of cases -- certainly on DEC machines -- signal ground is
connected to frame ground internally.
If a frame ground interconenction passes enough current to melt the wire,
then you've got significant voltage difference between the 2 machines.
That is a major safety problem if the 2 machines are close enough that
you can touch them. For %deity's sake sort out the wiring before somebody
gets killed.
If the 2 machines are far apart -- like in separate buildings, then you
should really be using some kind of isolated connection (either
transformer isolated or opto isolated) to avoid such problems.
-tony