This circuit uses a 7-segment display to indicate the logic level of a test circuit. The power supply is made with 5 V that can come from the analyzed circuit itself.
This circuit triggers a relay when a light beam that hits the phototransistor is cut off. The...
This flip-flop controlled by an LDR-type photocell was found in Radio Electroinics magazine from...
This circuit is from a publication from the 60s. The circuit, with minor changes, can be assembled with...