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 June 1978 issue of Radio Electronics magazine. The circuit is...
The slope of an object causes the sensor, a mercury switch to be triggered. The circuit activates...
This circuit for the logic control of the 555 in a power supply was found in the October 1989...