This circuit was found in an Electronics World of 1968. The transistor can be any general purpose and the double T must be set to R3 for the desired effect.
This setting appears multiple times on the site from different sources. This is from a 2000 manual...
A more efficient filter is the one that diverts the signal to the ground and not only short it, as...
This beat frequency oscillator was found in a 1980s documentation. The original FET has a grounded...