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 consists of a single Hartley oscillator using a bipolar transistor that can generate...
We found this circuit in a documentation about SCRs from the 70s. The circuit can be implemented with a...
This circuit was obtained in an old documentation, making use of an operational amplifier of the...