Console cables

[Paul Martin <PMARTIN%sri-stripe.arpa@CSNET-RELAY>]

The diagram from UPENN is correct for the cables for Hirose connections.
An earlier diagram distributed by Symbolics had the video signal and
ground gratuitously transposed, and this gave us grief in building
cables longer than a few feet.  Gore will sell you the cable, but they
want $4/ft for short lengths, and $11/ft for 200' type lengths.  This is
picking in the HIGH cotton!  Since we were unable to locate any other
source of a cable small enough to fit in the strain relief of the
Hirose, we resorted to building boxes that use cheapo cable to connect
them together, and have female Hirose connectors on them for short
male-to-male Hirose cables to hook up the CPU and the console.  For runs
of only a couple hundred feet, RG-59 coax is fine for the video, and
most any shielded cable of twisted pairs will do.  For runs up to about
500 ft, we've use RG-6 coax and independently shielded 25 gauge twisted
pairs.  We've had a bit of trouble with the audio on just one such
cable, so that may be stretching the flakey driver/receiver stuff used
for audio.  I'll have to experiment with whether a line of coax for each
twisted pair would allow a much longer run....  In theory, switching the
video onto RG-11 should be good for more than 1000 ft... we just haven't
had the need to do this experiment.

After we built a "cable transition box", Symbolics started to sell just
that sort of thing.  It uses an Ampex parallel push-pin style connector
for the 4 twisted pairs and their common shield, plus BNC connectors for
the coax, and exposes a male BNC and a female Hirose on the front panel.
It is designed for installation in a standard electrical wall box.  We
bought a bunch of these despite the rather steep cost of (at that time)
$45 each, and wired a dozen or so offices to a patch panel in our
machine room.  Hirose cables 20 to 50 feet long connect the CPUs to the
panel, and 10 ft Hirose cables in the offices connect the boxes to the
consoles.  When we needed more boxes recently, we ordered them and heard
the following bad news:  they now want $150 each for them, and they are
backordered until enough orders accumulate to justify a manufacturing
run.  Well, at theat price I suspect it only takes a few orders to make
a profitable manufacturing run, but I also suspect that not too many
people will rush to order them.  So we started looking for second
source; if we find one we'll report it to SLUG...  if we don't find one,
we may have to waste our own technicians' time designing and building
some for in-house use.  Too bad Symbolics has fallen onto such weird
times....

Paul Martin