16 Jun
2013
16 Jun
'13
4:43 p.m.
On Sun, Jun 16, 2013 at 09:49:53PM +0100, Tony Duell wrote:
Soecondly, IIRC the disptribution panel is essentially
just connectors.
It's certainly *mostly* just connectors, but the H317F panel also seems to
have four resistors (47 ohms) and a cap (not sure what 2R2uF means -- if they
meant 2.2uF they'd say that), and a 0-ohm jumper to disconnect the cap (for
higher bit rates IIRC). Last time I went digging for schematics I couldn't
find them, either online or in any of the mounds I keep tripping over.
I'd love to find prints -- I've got a dinky little multiport RS232-to-20mA
design I'd like to finish up, and having the H317F-style Berg connector on
it would make it very easy to wire to existing DZ11C installations (vs.
transferring all the screw terminals). But I also would get a kick out of
doing a PCB layout for a clone, if that would help (I have only the one
H317F so, sorry I can't spare the real thing).
Given that the current loop signals are pretty low
speed, you would
almost certainly get away with taking a length of ribbon cable, putting a
BERG socket on one end, splitting the other end into individual wires and
puttign them on screw terminals.
I don't know if 9600 baud counts as high speed but I was *very* happy with
my DZ11C back when I had a PDP-11/34 in my college apartment. My room was
at the far end of the house and running 9600 baud through ~125' of untwisted
unshielded Radio Shack telephone wire (stapled along the baseboards) was
hopeless with RS232 (DZ11A), but 20mA worked fine through the same cheapy
wire once I wired up a grounded outlet for the VT100 (but not until then).
But yeah, with 20 mA, 110 baud is a lot more popular, and at that speed you
could probably direct-bury magnet wire through the yard and get away with it.
You barely need wire at all!
John Wilson
D Bit