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.
This circuit was obtained from a 1978 Practical Wireless. It makes a speaker emit sound when there...
This circuit was found in a 73 magazine for radio amateurs from the 90s. The circuit uses high...
This circuit was found in an American 80's documentation. The transistor is of germanium of the...