[GreenKeys] M15 with Polar Relay -- Configuration

[Paul Birkel]

Good morning all;

 

I seek some guidance/experience with setting up an M15 that came equipped
with a polar relay and otherwise essentially  "factory fresh" wiring
harness.  My basic question is whether I can swap the relay for a non-polar
one and then use the M15 "conventionally" . and if so, what would be the
substitute relay?  And then . does anyone have such a substitute available
for employment in this endeavor :->?

 

Alternatively, I do have another polar relay and definitely have more than a
"passing interest" in leaving the M15 as received and instead setting up a
local polar circuit to drive it that would in turn be patched into a normal
local loop.  There's not been much discussion of practical setup/employment
of polar circuits here AFAIK; I enjoyed reading the AT&T Long Lines book on
"Principles of Electricity" back in 2019 and intend to refer to it again
before I proceed.

 

I originally received the M15 from an ex-MARS guy who eventually used it as
an office printer with an early microcomputer system before putting it into
storage a few decades ago.  He kept it well lubricated, thank goodness.  It
appears to be configured using a standard 60 mA pulling magnet (no S/P
switch nor a 3-position terminal block; the rangefinder does NOT have an HM
marking; and the magnet definitely has round windings).  I haven't yet
checked the resistance on the loop to be triply sure.

 

My main terminal block appears to be physically different from that shown at
http://www.baudot.net/gil/tty-machines/pics/M15-KSR-Gil-Iface-Terminals.jpg
I don't know whether that's significant.  It appears to be configured to
separate the KBD from the PTR circuits.  The M15 wiring appears to be
entirely original excepting one modification at the polar relay - which is a
coaxial-cable stub (clipped off after ~2" and left hanging) attached to the
rearmost pair of polar relay terminals that appear to have been otherwise
unused (but can't quite be sure of that, although there are no telltale
snips that I can spot).  Possibly that's a remnant of the earlier MARS use,
and the separated KBD/PTR circuits reflect the later office-printer use.

 

Possibly the use a M15-polar configuration is documented in some RTTY
publication?  At the moment I'm using the "New RTTY Handbook" as my starting
point, but I imagine that there are other specific how-to articles .

 

Your various and sundry thoughts and observations will be much appreciated,
thank you.

 

Good Health to You and Yours,

paul

 

 

 

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