This circuit takes advantage of the hysteresis of a relay to provide a latching effect. The circuit acts as a trigger and the components must be according to the used relay.
This useful inductance bridge was found in a Radio Electronics from September 1963. The...
This circuit is a handset receiver that picks up the signal emitted by a coil under the rug or...
This circuit found in the October 1975 issue of Radio Electronics magazine uses an integrated...