This circuit uses two relays that switch when the voltage exceeds the value given by zener D2. The circuit is from a Radio Electronics magazine from April 1975.
This circuit uses two oscillators to produce a sound that seems the sound of a ring-bell. The...
This circuit is suggested by General Electric in 1966 documentation. The Triac must match the...
Found in a 90’s Popular Electronics, this circuit generates sinusoidal signals with frequency...