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.
Other operational amplifiers series, such as the MC34072, MC34074, MC35071, MC35072, MC35074 or...
We found this circuit in an English publication in 1982, but it can still be easily assembled by...
This conventional slow-moving circuit uses incandescent light bulbs, but can be changed to use...