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 configuration with the LM111 was found in your factory manual. The circuit can be implemented with...
The double T of this circuit makes it amplify only the 1 kHz signals. The circuit can be used as a...
This car alarm was obtained in a Signetics documentation from the 1980s. The circuit uses the 555...