This 1.5 A circuit has the output voltages adjusted by a selector switch. We found it in a Popular Electronics from the 90s. The integrated circuit must have a heat sink.
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...