These optical relays, which can act as a shield, were found in an American documentation from the 1980s. The circuit has a LDR sensor. It can be adapted for other types of sensors.
This old circuit for circuit breaker cars was found in a 1963 publication. The transistors are...
This circuit was obtained in a 1973 national publication, translated from an English publication of the...
Found in an October 1992 Radio Electronics magazine article, this circuit generates a low-power tone in...