This circuit was found in ancient American documentation. It provides a 70 Vpp signal at frequencies up to 100 kHz. Observe the high supply voltage.
In the circuit of the figure, when pressing S1 the sound varies according to the value of R2 and...
This switching circuit for contact breaker cars was found in a Radio Electronics from April 1964....
This inverter amplifier is from a 1992 publication. NPN transistors can be BC548 and PNP BC558....