This circuit was found in the August 1996 Electronics Now magazine. The circuit is based on an operational circuit whose type determines the gains and limits for the frequency.
This simple version of a function generator with the XR2206 was found in the May 1977 issue of...
In a modern version this circuit can use an LED in series with a resistor in place of the lamp. The...
This VFO was found in a 1980s documentation. The central frequency is given by the crystal and the...