Suggested by a Popular Electronics from the 90s, this circuit triggers an external load, relay or recorder, when the telephone line receives a call, thus enabling its recording.
This circuit was found in the 1972 RCA Power Transistor Databook. Transistors are uncommon today,...
This circuit is used to light a 20 W fluorescent lamp from the 12 V of a car battery. The...
This circuit fires by burning the fuse when the input voltage exceeds the value referenced by the zener....