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.
In the figure we have a high stability voltage reference, providing a voltage of 10 V at the...
We find this circuit in an American 1980s documentation. Integrated circuits are uncommon today as...
The diagram is from a 1990s document. The integrated circuit must be equipped with a heat sink. The...