Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the Sonalert type with included oscillator.
This circuit was obtained in the SGS manual of linear integrated circuits of 1982. The components used...
This circuit can provide a maximum load current of 1 A. The integrated circuit must have a...
This circuit was obtained from the September 1971 issue of Radio Electronics magazine. The 709 is an...