Employing the XR2206 IC, this circuit was found in the May 1977 issue of Radio Electronics magazine. The formula next to the diagram gives the component values as a function of frequency.
This circuit using an operational amplifier was found in old American documentation. It can be...
If the circuit oscillates, emitting sound, it is because the transistor is good. This simple...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...