In this circuit of an American documentation of the 90s, when the light is cut, we have the production of a pulsating tone. R3 determines the trigger sensitivity.
This circuit was found in the December 1977 issue of Radio Electronics magazine. The circuit uses...
This is an improved version of the previous circuit that includes speed control. The engine can be...
This electronic siren circuit, found in a 1982 documentation, uses three oscillators mounted...