4 Jan
2006
4 Jan
'06
4:37 p.m.
Relay logic can depend on more than simple make/break on
coil-current-present types.
Stepping relays were used in telephone and logic systems. I used to have a
telephone relay with two windings on the same electromagnet. I'm not sure,
but I suspect the two might have been used as sort of a logical "AND"
function. Latching relays use multiple coils also.
Mutlipe windings on telehpone relays can have many functions, including
acting as an inverter (pass a constant current through one winding, the
relay pulls in, pass the same current through the other winding in the
opposite direction, the magnetic fields cancel, it drops out), provinding
2 inputs to the relay (either or both coils energised in the same
direction will make it pull in), and even acting as an audio transformer.
-tony