Originally designed for WWV (Standard Time Station) signals, it lets 1 kHz tones pass by rejecting the 440 and 600 Hz tones emitted by the station. The circuit is from a 1964 Electronic Design.
This circuit uses a capacitor to store energy. The capacitor is charged by closing S1 by a moment. Them,...
This circuit is both a signal injector and a signal follower. A key selects the operating mode. The...
The difference between this circuit and the previous one is that it uses PNP transistors. The...