This circuit is for traditional old-style telephone lines found in an American 1980s documentation. Components are common and the optical coupler can be replaced with an equivalent.
Placed near a common receiver, this oscillator is intended to generate a beating signal to receive...
CMOS integrated circuits are sensitive to supply voltages in terms of signal propagation time....
Found in a radio amateur magazine of the 1980s, this circuit uses components that can still be...