This circuit, very critical due to the frequency at which it operates, was found in an American documentation that uses a resonant cavity in a beer can. The transistor can be of any type for RF.
This triac circuit was taken from an article in the July 1970 Radio Electronics magazine. Note the...
Signals ranging from a few millivolts to a few volts can be used to excite a relay with this...
This circuit was found in American documentation from the 90's. The transformer determines the...