We found this circuit in the September 1971 Radio Electronics magazine. The SCR can be any of the 106 series and the buzzer can be replaced by a relay according to the supply voltage.
This circuit that triggers an SCR was found in volume 5 of the 1995 Encyclopedia of Electronic Circuits....
This 1-transistor oscillator circuit was found in the March 1965 Radio Electronics magazine. The...
Found in a 1964 CQ magazine this circuit consists of an automatic telegraphic key, providing the...