This circuit was found in a 90s American publication. The same configuration appears in several places on this site, obtained from different sources. The lamps can be replaced by LEDs.
This code switch was found in a 1990 Electronics Handbook. It can be mounted with BC558...
These simple weapon and target circuits with emitter and photoelectric sensor were found in a 1985...
This circuit found in a 1988 documentation, uses a piezoelectric or crystal capsule as a...