This receiver for a modulated light intercom was found in a 90s Elektor. The audio amplifier can be replaced by an equivalent. The sensor can be any phototransistor.
We found this circuit in a publication of 1990. With the changes it can be mounted easily today....
This simple photometer was found in a 1977 Radio Shack manual. The sensor is a photocell, which can...
This circuit is used to test a triac and also to teach how it works. The load is an incandescent...