We found this circuit in the Encyclopedia of Electronic Circuits Volume 5 from 1995. It uses a 3-terminal transducer from the time. The circuit is triggered by light.
This is the circuit of a turntable from the 1970s. We found it in a repair article in the December...
This circuit divides the grid 60 Hz frequency to obtain 20 Hz to drive mechanical watches used at...
This small audio amplifier uses an uncommon integrated circuit today. The circuit is from a...