singing petula clark there.g off singing careers and directing the second world war the microphone was clearly doing something right operationally, too. eyes had been on the groundbreaking ribbon microphone invented by rca, the radio corporation of america but it was a little too expensive. so in true bbc form, they made their own for less than 10% of what rca were charging. nice going. the type—a stayed in use by the bbc from 1934— 1959, a whole 25 years. that is a long time when technology was developing so rapidly. so what about inside? the type—a is called a ribbon microphone. that's because behind the perforated cover is exactly that, a ribbon of metal. with the help of one of the trusty bbc engineering manuals, we can see that soundwaves come in from either the front or the back and hit the ribbon in the middle. so thin that it flexes and wiggles when the noise vibrations in the air hit it, just like your eardrum. the flexing moves the ribbon through a magnetic field created by two magnets on either side.