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 circuit generates a sinusoidal signal with only -80 dB THD. The circuit was found in a 90's...
This test, the commercial transistor tester, had its diagram published in an article in Radio...
This circuit can supply voltages in the range of 8 to 20 V with a maximum current of 3 A. The...