[GreenKeys] WW-II Model 15 curiosity.

[Jim Haynes]

Just when you think you have it all figured out something comes along to
show you that you don't.

With Model 15s, I'm aware of holding magnet selectors where the selector
coils can be connected in parallel for 60ma operation or in series for
20ma operation.  But I thought all the pulling magnet selector models
always had the magnets wired in series for 60ma operation.  The parts
book shows the magnet is 177M, 105 ohms, and I just measured a few of
them and found them all to have about that much resistance.

I was just cleaning up a WW-II Model 15 cover and there is a red decal on
the copyholder.  It says to check the magnet wiring before placing the
unit in service, shows wiring diagrams of series and parallel connections,
says 1020 ohms next to each.  Shows parallel connection for 60ma and
series for 20ma and cites MWO SIG 82.  And the picture shows the round
selector magnet coils typical of pulling magnet selectors, not the holding
magnet kind that has more squarish coils.

I have a TM 11-352, which is just a War Department cover letter in the
front of Teletype Instruction Manual No. 11.  The W.D. letter is dated
December 1943 and the Teletype title page shows April, 1944.  The
instruction manual is simply the collected Model 15 bulletins, plus
wiring diagrams, plus some notes peculiar to the military configuration
where the crates serve as table and seat for the machine and operator.
There's nothing in this manual but the pulling magnet selector with 177M
magnet coils wired in series.

I see there's a more recent issue of TM 11-352 up on ebay right now, but
I don't care enough about this trivial issue to want to buy it.  Still,
I'm curious about this MWO, and whether the coils really are 1020 ohms
each, which seems awfully high, and whether anybody has ever seen one
of these machines.