[GreenKeys] Re: W.U. Motor Control Relay

[Jack]

ZCZC

That "old" motor control relay was used in the early Bell System
service order 15's.
The TTY's operated against ground on a single telco pair. One side
of the
pair was the inverted neutral TTY signal (no current was a mark)
and the
other controlled the relay. Eventually, those old solenoid type
relays were
replaced with the "Model 28" type relay, the small black plastic
enclosed
unit, since the old ones were no longer available. The only thing
that
went bad on the old realys was the contacts...the coils would last
forever.

Jack WA2HWJ

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