This circuit recognizes a tone determined by the tuned input circuit (R3 / R4 / C2). The circuit was found in Radio Electronics from the 90s. The 4046 is not a common component today.
This circuit was obtained in a 1978 magazine, but it can be easily assembled. What the circuit does...
With this circuit it is possible to use a pair of old telephones in a wired communication system. The...
This remote-control transmitter for the 27 MHz band was found in the November 1960 Radio...