This circuit has an interface for a multimeter or electronic voltmeter. We found it in a 90s Electronic Engineering. The sensor is an unusual component today.
This circuit is used to cut the “click” in the loudspeaker of amplifiers when they are turned on....
Found in RCA documentation from the 1970s, this circuit is intended for firing thyristors in inverter...
In the figure we have the way to control a TIC series triac with a reed switch. The current in the...