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 was obtained from a Popular Electronics of 1994. The magazine no longer exists in its...
The LM3909 tone generator integrated circuit of this application is uncommon nowadays. The circuit...
The traditional circuit was taken from a French magazine Radio Plans that no longer exists but can...