This circuit was found in an Elektor from the 90s. Next to the circuit we have a table with the delays obtained when the circuit is connected according to the positions of the selector switches.
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...