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

[jhhaynes at earthlink.net]

In the typical setup I'm talking about the signal is a neutral loop;
but they use polarity of the loop current to control the motor.  And
in this setup there is only one machine on the line between customer's
office and the telegraph company office.  As in neutral-loop Telex they
used the polarity of loop current for motor control.

In a circuit switched system you can use motor control to tell the
operator that a connection has been made and it is OK to start
typing.  Reversed current in the loop keeps the motor off at the
customer's end, but still allows the customer to send a break to
get the attention of the operator at the telegraph office.


jhhaynes at earthlink dot net