My Tech2 blog doesn't seem to have been playing (you can still read it, but I can't edit it) but I really wanted to write about carbon microphones, so I'm writing it here instead! The reason I want to write about them is because they've got a really interesting history, but I'll try to keep it short.
The technology was developed in the 1870s. David Edward Hughes is seen as the inventor (1) but Thomas Edison and Emile Berliner were fighting over the patent (2). As well as this, David Edward Hughes is also thought to have coined the word 'microphone' (2).
Eventually, Berliner got the patent in 1877 (3) and it was bought by Alexander Graham Bell for use in telephones (2). It was good for that because the sound doesn't need pre-amplication because it gave such a high output anyway (1).
A diaphragm vibrates and creates a varying current through carbon granules (1). Of course, as there's a current, you need a battery (1). They do have some disadvantages, though. They've got quite a narrow frequency range and they often produced noise, but this could usually be solved by giving the microphone a bit of a shake to dislodge the granules stuck at the bottom (1).
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