Found in the September 1972 issue of Radio Electronics magazine, this signal injector is based on the HEP580. The circuit is powered by two batteries and its frequency is basically given by C1.
In the circuit shown in the figure, we add a capacitor (C2) and a resistor (R4) at the base of the...
Indicated for calibrating digital instruments and circuits, this circuit was found in the June...
Found in an old English publication this circuit uses a dual gate MOSFET. Coils not specified....