This circuit was submitted to Broadcast Management and
Engineering magazine's Great Idea Contest in 1987 where it
was awarded the National First Prize. This circuit was designed at the
request of Carl Hanson at KNX-FM and designed by Mike Callaghan, chief
engineer of KIIS-FM, Los Angeles.
How it Works When power is first applied to the circuit, the
parallel combination of C1/R2 is charged to 1/2 Vcc through the voltage
divider R1/R2. When S1 is closed, C1 discharges through the coil of
RL1. This pulls in the relay. The wiper is held in by the current
through RL1 and R1.
Any charge remaining on C1 discharges through R2, so when S1 is pressed
again, C1 (now a short circuit) releases the relay, returning the
circuit to its original condition.
What results is a toggled push-on/push-off action. The momentary switch
can originate from another machine or switch closure.