Found in a Popular Electronics from the 90's, this circuit detects the approach of objects by the reflection of the radiation emitted by the LED. The relay is a 12 V sensitive type.
We found this circuit on Radio Electronics from July 1990. It triggers a relay with a touch of the...
These three circuits have different treble responses. We found them in the February 1970 issue of...
This photoelectric cell light relay was found in Radio Electronics magazine from April 1958. The...