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 simple signal injector oscillator was found in a 1981 documentation. The coil can be made...
September 2017 - Würth Elektronik High Power Ultraviolet LEDs can be obtained from Mouser...
This circuit works as a variable transformer that measures the power applied to a 110 V load (and...