This circuit was found in a 1966 General Electric book. The triac and the day are from that time and can be replaced by modern equivalents depending on the load.
Here we show how two 4017s can be cascaded to count above 10. The circuits are driven by a square...
The circuit in the figure represents a typical application of a phototransistor exciting a relay...
This circuit, in fact, what it does is a reactivation of the batteries through a brief pulsating...