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Communicating through copper wires using electrical signaling at audio frequencies is _very_ different from communicating through air using acoustic waves. Even
by mbell 13y ago
Communicating through copper wires using electrical signaling at audio frequencies is _very_ different from communicating through air using acoustic waves. Even assuming 'perfect' speakers and microphones you have completely different transmission effects than you have with low frequency electrical signals in copper.
- rahimnathwani 13y agoDidn't some old modems use an acoustic coupler (i.e. a cradle which held the handset)?
- prof_hobart 13y agoYes, they did. I've still got an old one in a cupboard somewhere.
- stedaniels 13y agoPlease do thorough research. Modems were originally, more often than not, used with acoustic couplers.
- cnvogel 13y agoExactly! And the DIY version of it looked like this: http://commons.wikimedia.org/wiki/File:Akustikkoppler_CCC_Datenklo.jpg http://commons.wikimedia.org/wiki/File:Akustikkoppler_CCC_Da... And it supports 300bps and 1200bps speeds.
- mbell 13y agoIt's unclear what difference that makes in the context of my post. The fact remains that the modulation and signaling protocols developed for use in modems were designed within the constraints of electrical transmission across miles of copper wire, not through sounds waves in an unknown acoustical environment. The constraints for the two situations are entirely different. Acoustic couplers are designed to minimize any acoustical impact of their use to avoid the exact acoustical problems you'd have transmitting across a room.
- smithian 13y agoYes. Also, the upper limit on the dynamic range of the telephone network is somewhere around 3400 Hz, well within the range of human hearing. This protocol is designed to send data in a frequency range that most people can't hear, or at least can't hear very well.
- stedaniels 13y agoPlease do thorough research. Modems were originally, more often than not, used with acoustic couplers.
- rdeboo 13y agoWhen I was a child (probably over 20 years ago) I would watch my mother transfer text documents via the computer. The modem was a device that exactly fitted the telephone horn. So you had to pick up the phone, dial the number, then put the horn in the modem. I don't recall exactly but I think you could hear the computer "talk" to the other side. I'm not sure how different that technique is from what is posted in this article.