This optical coupler for short distances is powered by 12 V which is the voltage of the lamp and the relay. The circuit can also use emitting LEDs and the phototransistor can be of any type.
This sensor circuit from a 1967 Ferranti documentation uses components from the era. The circuit...
This circuit was found in the November 1992 issue of Radio Electronics magazine. The circuit has...
This circuit eliminates hiss and other noise from audio sources by cutting frequencies above 10...