This circuit is for old telephones with analog lines. It was found in the May 1988 Radio Electronics magazine. The circuit is powered by the line signal voltaje.
Found in a 1963 documentation, this circuit employs germanium transistors of the time. Transformer and...
In the figure we have a way of receiving ultrasonic signals of a single frequency using a PLL 567....
This traditional circuit generates a 200 Hz sinusoidal signal. The frequency depends on the...