This voice scrambler and descrambler circuit was found in a Radio Electronics from July 1963. Transformers are common types at the time with impedances according to telephones and line.
This amplifier with differential input uses two old op amps but can be implemented with modern op amps....
The main feature of this circuit is that it provides a sine waveform signal. In this circuit, the...
The HA2620 integrated circuit used in this comparator is from the 80's, but the setting can be...