This is a circuit suggested by Linear Technology in a 1980s documentation. The integrated circuit is from the era. Observe the input and output voltage.
The circuit is suitable for calls in a residence and was published in the Radio Electronics...
The input impedance of this circuit is about 700 k ohm and the output impedance is about 1 k ohm....
With the values of the components indicated, the circuit generates a 1 kHz signal. The power...