Marconi ribbon microphone, used by the BBC, English, 1934-1959.
© Science Museum / Science & Society Picture Library
A radio microphone is a transducer, which is a device that translates voltages and currents into sounds, lights and forces. The tiny presure changes, caused by the aluminium ribbon which is les than a thousandth of a millimetre thick, vibrate between the poles of a large magnet. These generate currents which mimic the sound wave.