This power control circuit was found in an article in the June 1995 Electronis Now magazine. The circuit makes use of a trigger transformer.
The idea is simple: using a flashlight to cut your TV commercials triggers a relay that turns off...
Found in documentation from the 70s, this circuit uses an operational one from that time. It goes for...
Found in a Popular Electronics from the 90s, this circuit uses thermistors for low noise...