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 25 W phase photo control was found in a 1965 General Electric publication. The circuit uses a...
The circuit below uses common JFET transistors, which can be the BF245 or MPF102 amplifying video...
This circuit was found in a 1997 documentation. It works as a booster for VHF and UHF signals...