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 drives two-color LEDs at a speed that is set in the 100k pot. The circuit can be...
The circuit shown was found in a 1967 RCA manual. Modern equivalent components can be used. The...
Indicated for automotive applications, this circuit was found in the November 1980 issue of Radio...