This circuit is from General Electric from the 80s, using a relay with high current contacts (20 A). The transistor admits equivalent, and any phototransistor can be used as a sensor.
This Schmitt trigger was found in old documentation. The transistors can be of the general-purpose type like...
This circuit can be used with previous transmitters to decode a signal transmitted via power grid....
This circuit was suggested by General Electric in a 1965 documentation. The circuit can be...