We found this circuit in an Australian documentation from 1991. The circuit is suitable for SMD mounting thus making it very small. The circuit was sold in a kit at the time.
We found this ladder-shaped signal generator circuit in Radio Electronics magazine from August 1966....
This circuit has a 200 kHz bandwidth and a low input current. The circuit is from the 80's, but...
This circuit, from an American publication of 1964, generates two tones determined by the double T in...