We found this solid-state relay circuit that can function as a shield in a Radio Electronics magazine from December 1989. The optocoupler is a phototransistor type.
This infrared emitter (pulsating) can be used with several other alarm and remote-control circuits on...
Signals of up to a few tens of kilohertz can be generated by this circuit found in a European...
This amplifier was found in a technical documentation from the 1970s. The circuit uses 2N2218...