Using a 4046 PLL this circuit recognizes a 1.6 to 1.8 kHz tone by driving an output LED. The circuit is from a Radio Electronics from December 1989.
This circuit is from a 1976 documentation. The diodes can be 1N34 or equivalent, and the power...
This circuit is from a high voltage tube source. It does not include the filament voltage that must...
This circuit is from the Motorola Linear Databook of 1990 and can be implemented with other...