This circuit with the 555, was obtained in a 90s American documentation. The signal must be applied to a good amplifier. The sound is similar to that of a police siren.
With this circuit, we can have a remote frequency control of a tuned circuit. Lx is the coil of...
This circuit for incandescent lamps was found in the February 1972 Radio Electronics magazine. The triac is...
Suggested by an old Popular Electronics, this circuit is based on an uncommon integrated today,...