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 circuit is from a Radio Electronics magazine from December 1958. The indicator instrument is analog...
This circuit sends signals to a shortwave radio (range 3 to 7 MHz) at a distance of a few tens of...
This circuit was found in an Electronics World of 1968. It can be applied to any modern triac and...