This circuit is from a 1968 documentation using one of the first integrated circuits available at the time, the TAA370. The circuit is powered by 1.3 V using a 200 ohm handset.
Using LM3909 integrated circuits, this circuit was found in an American documentation from the...
This circuit was found in an ancient American documentation. The components of the time are not...
This circuit with low impedance output and 900k input impedance was found in the October 1993...