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 test consists of a simple Hartley oscillator using a transformer of the type found on older...
This circuit, from a 1985 documentation, produces several types of sound effects selected by the...
This 6-transistor receiver was manufactured in Japan in the 60s. The circuit is superheterodyne and has a 6V...