We found this circuit in an old publication. The components used are rare today. Accuracy depends on the resistors in the input selection network. The circuit operates from 10 to 500 kHz.
This circuit generates sinusoidal signals between 300 and 3000 Hz. We find a 303 Circuits from the 90's....
This amplifier for audio transmission lines was found in a 1961 American publication. The critical...
Old phones with dials can be used in a simple home intercom system, as this circuit from Popular...