Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
We found this easy start circuit in Electronics Now magazine from December 1993. The frequency is...
Found on a 1964 CQ this circuit is intended for tone frequency change modulation (FSK) telegraphic...
This VFO was found in a 1980s documentation. The central frequency is given by the crystal and the...