We found this circuit in an old documentation, but it is still current. General purpose transistors can be used, and the SCR can be the TIC106. The bell is a transducer with an oscillator (buzzer).
This circuit produces a signal in the range corresponding the the VHH channels between 2 and 6....
The circuit presented is from a 1969 Radiorama magazine (Italy), and can be designed with more...
The maximum power of the controlled load depends on the triac used. The circuit is from a Radio...