This PA or Public Address amplifier with a few watts of power was found in the March 1986 Radio Electronics magazine. It uses two LM380 ICs in bridge mode for higher power.
This circuit, from a 1973 documentation, can be made with BC549 transistors. The frequency depends on...
Suggested by General Electric in a 1965 documentation, this circuit can use the TIC106 as an SCR....
This circuit is from an old Popular Electronics. The circuit is based on a 555 and a 5V voltage...