[GreenKeys] Another button question

[Jim Haynes]

I don't know how common it was to have a motor stop function.  On Model 15
there was a function operated by FIGS H that would latch the motor circuit
open.  It would be restored closed by any spacing signal on the line,
not specifically a break.  This is visible as a lever that engages the
selector magnet armature to detect the spacing signal.

Some Model 28 machines have a stunt box combination that operates on
FIGS-BLANK-H to stop the motor, and any spacing signal on the line
restarts it.  This makes use of a special latching relay mounted in the
LESU.  The relay has one winding connected with the motor stop contacts
in the stunt box and operated off the power line.  The other winding is
in series with the signal line and unlatches the stop contact whenever
the line goes spacing.

There are other motor control options.  One is a timer that turns off
the motor after the signal line has been steady marking for some period
of time.  Any spacing signal will restart the motor.  One version of this
seen in the M28 parts book uses two gears to produce the time delay.
Others, including some third-party ones, use electronic timers.

Then there are schemes where line current polarity controls the motor.
Line current is always on, so the outlying station can signal the central
office by sending a break.  But the polarity is such that the motor is
turned off.  When the central office connects to the out station the
line polarity is reversed and that turns the motor on.  This was popular
with Western Union.  It may also be used in Telex - I don't remember.

Some Model 15 machines have a solenoid motor control relay.  I've never
seen how this is used.  Maybe some of the ex-telco people on here can tell
us about it.  And there is a picture of a similar relay in the Model 28
parts book.

 	---

 	"Ya can argue all ya wanna, but it's dif'rent than it was."
 	"No it ain't! No it ain't!  But ya gotta know the territory."
 		Meredith Willson, The Music Man