This circuit was found in American documentation from 1966, but it can be assembled with a modern equivalent transistor. The circuit is based on a mechanical tuning fork with a coil feedback system.
This circuit for PC and which can also be used with microcontrollers was found in an English...
This two-tone decoder has a bandwidth of 24%. The circuit is from a 1994 Electronics Now. The...
The LMV321 is a low voltage operational amplifier from ON Semiconductor. The following diagram,...