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.
In the figure we show another interesting application for integrated circuit 4001. This circuit...
This audibility or loudness control for sound equipment is from 1992 documentation. The circuit uses...
This circuit was found in an application note of the LTC1164 from Linear Technology of the 1990s....