🚀 go-pugleaf

Here is my promised posting of the solution to my 2 wire serial
problem.  I got two answers (one of them by several people).

The first answer would be very expensive and unprofitable.  This was
to get a pair of short-haul modems (about $300) at a fixed baud rate(
2400 I believe).  Anyway, This was not viable, because a network at
2400 would be unbearable.

The other solution I have posted below.  It is very good, however, I
am unsure whether or not it works, because I finally convinced
telecommunications to let me rewire the jacks (the 4 wire had been
run, but only 2 connected.)

Anyway, Thanks again to all who sent me the ideas.

^Mark,
^You actually have three wires available. The two in your room and
^ground.  The best option of all would be to use the phone ground.  If
^the phone system is hooked up in a standard way, one of the leads in
^the phone box will be ground.  You can use this ground for both the
^phone AND the RS-232 ground line since the potential of the dirt is
^the same in both cases (phone ground should be an actual ground -- if
^it's not, see the water pipe option).  This works less well with
^farther distances, but the phone ground is probably identical (within
^50 mV or so) in both rooms anyway.  To check if the phone ground is
^a real ground, measure the resistance between it and a water pipe
^(metal - metal pipes go into the dirt), though it actually doesn't
^matter as long as both phones are on the same ground circuit.  Another
^way to check the line would be as follows:
^
^            Room 1                 Room 2
^            ------                 ------
^
^       ---> A1 -------[    ]        [    ]------- A2 <----[VOM]
^       |       RS-232 [wall]        [wall] RS-232          | |
^       |--> B1 -------[    ]        [    ]------- B2 <------ |
^       |                                                     |
^       |                                                     |
^       ---> G1 -------[    ]        [    ]------- G2 <--------
^
^Tie all three wires together in 1 room.  Measure resistance between
^phone-net wire 1 (A2) and phone-net wire 2 (B2) -- it should be
^low (like 100, 200 ohms) -- if so, that means that the 2 wire setup
^is hooked up OK, no measure either of the phone-net lines in room 2
^(for ex. A2) to the ground in room 2 (G2).  If that is low too, it
^should all work fine.
^
^Note: Make SURE that the ground wire is used ONLY for the RS-232
^ground, NOT Tx or Rx -- hooking either of these to ground might
^fry the computer (the computer can't drive the dirt to +/- 12 VDC,
^and if it tries, it will probably fry).
^
^Other ground wire options include:
^    Since you are both in the same building (I infer from your post),
^    you can both hook the RS-232 grounds to the building ground to
^    complete the circuit.  If possible, you would use a water pipe,
^    then a building frame ground (assuming it is really grounded) --
^    many times window frames, door frames will be connected -- you
^    need to check this first.
^
^    Last choice would be the ground in a 3 prong outlet -- this is
^    dangerous if the building was not wired correctly.  Sometimes the
^    ground wire is wired to the neutral wire or even worse the hot
^    wire.  If so, this becomes dangerous.  Also, I don't like this
^    option since it puts a wire near 120 VAC.
^
^                                        Good Luck,
^                                        Rob Ginn
^                                        eraps1@nadc.arpa
-- 
------------------------------------------------------------
All opinions are my own, as are the spellings any deviation
from the norm is just an effect of late nights and early
mornings, with little sleep between.