Found in a 90s Elektor, this circuit is based on a Maxim integrated circuit of the time. The circuit supplies 5 V at its output with a maximum current of 50 mA.
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...