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by jasomill
538 days ago
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Fascinating article. See also https://web.archive.org/web/20120314023131if_/http://www.alc... for an early technical article describing the implementation details of the familiar DTMF "touch tone" dialing system, noting that the precise details differ from the final implementation — in particular, the high group frequencies increased from 1,094/1,209/1,336/1,477 Hz to 1,209/1,336/1,477/1,633 Hz, possibly to mitigate the "pulling" effect described on pp. 251–252 (though I can find no reference for the rationale). |
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