This circuit is from a 1976 amateur radio manual. The transistor can be the BD136 and the frequency adjustment is done in a potentiometer. The supply can be done with voltages from 6 to 15 V.
This traditional configuration is from a 1976 publication, showing that nothing has changed since...
We found this circuit in a Radio Electronics from May 1959. The circuit uses a power relay and a...
This metronome was found in a 1979 publication, but it can be assembled more easily with the BC548...