14 Nov
2006
14 Nov
'06
10:57 a.m.
Jim Beacon wrote:
From: "Gooijen, Henk" <henk.gooijen at
oce.com>
I once worked on a new system that had RS-232 levels
operating at 0 and 5 volts. The old terminals, however,
required at least -3 volts to work. Had to design and
build a small amplifier to convert the levels for about
15 terminals (without using an external power supply
for each one[*]). Yuck!
[*] No external supply, due to a lack of available outlets,
and the constant "I needed an outlet for ..., and I didn't
think that was important ..." problems.
So, Don ... cache is indeed optional, UBI (as I
found out) is not!!
Tomorrow I will check the power supply voltages. +5.1V is expected
to be OK, but the +/-12V ... hmmm, how come that the RS-232 signals
to and from the VT100 are working ...?
Because the VT100 will accept valid signals down to about +/- 3V before it
gets confused (a lot of people get caught out on PC serial ports, as they
don't usually drive to the full RS232 levels, and some kit needs the full
level).
Jim.