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.
Generating sinusoidal signals from 1.5 to 15 kHz, this oscillator uses common complementary...
This circuit, found in a publication of the year 1968, uses a MOSFET at the input to increase...
This circuit maintains on a flashing LED at a frequency determined by the capacitor. The...