This old voice circuit suitable for telephones of the time was found in a Radio Electronics from September 1973. The circuit is powered by a voltage of 7 V.
This circuit was obtained in an Electronics World of 1969. It is a crystal oscillator with a 100...
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...
This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made...