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.
The circuit shown in the figure generates a rectangular signal whose frequency depends on C1. For...
This circuit suggested by Texas Instruments, operates with pulses, and is based on an operational...
This circuit captures, through a coil, the signals emitted by another coil under the mat connected to...