This alarm oscillator was found in the December 1974 issue of Radio Electronics magazine. The power transistor must be equipped with a good heat sink. The Frequency basically is given by C1.
Found in the October 1992 Radio Electronics magazine, this oscillator is controlled by switch S1....
This circuit was obtained in a 1976 amateur radio manual. The circuit can be made with a 2N2222...
The component used in this circuit is not very common today as the circuit is from the 80's. It...