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Re: Speaker Vs. Microphone

On Fri, 11 Aug 2000, Tom McCarthy wrote:

If Bell successfully transimitted the human voice,
wouldn't that classify as the first microphone?

The early commercial telephones were "sound powered", and basically were
two loudspeakers connected together without a power supply. Modern
"dynamic microphones" are the same as little bitty loudspeakers. What
exactly does the word "microphone" mean?

I know that Edison came up with the carbon microphone, which is not a
transducer in the usual sense. The diaphragm changes the resistance of
the carbon, and with a battery as a power supply, this forms a crude
amplifier. Signals are amplified, not just "transuced," so the carbon mic
is not just a microphone. Carbon microphones are interesting toys:
connect one to a battery and a loudspeaker, then place the carbon mic near
the speaker, and you create feedback, proving that amplification is
occurring. Or, glue a rod between a speaker cone and the diaphragm of a
carbon microphone. This forms a signal amplifier, just like a vacuum tube
or transistor. The Professor on Gilligan's Island with enough time could
have built an entire electronics infrastructure using charred-cocoanut
carbon amplifiers instead of vacuum tubes!

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