Found in an American documentation from 1968, this circuit senses the temperature through an infrared sensor of the time. The indicator is analog.
This was a very popular instrument in the workshops of the 60s and 70s. It was a "top of the line"...
The idea is simple: using a flashlight to cut your TV commercials triggers a relay that turns off...
This circuit is from a Popular Electronics from the 90s. The integrated circuit admits equivalents...