This circuit was found in a 90s Wels' Think Tank. The frequency depends on C2 and R3. The handset or speaker must be at least 80-ohm. Observe the low supply voltage.
The amplifier shown in the figure was obtained from the Anlog Devices linear integrated circuits...
If the reader still uses silk screen printing tables this is an interesting circuit found in a 1994...
This circuit monitors the output of a stereo amplifier, checking the balance and balance between...