We found this circuit in the July 1990 issue of Radio Electronics magazine. The frequencies are given by capacitors C2 and C3, which can be changed.
This circuit had its assembly described in a Radio Electronics from March 1963. The circuit uses 2...
We found this configuration in a documentation for radio amateurs from 1974. The circuit can be...
We found this circuit in an English documentation from 1989. The integrated circuit used is not...