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The Sound of the Dialup, Pictured
If you ever connected to the Internet before the 2000s, you probably remember how it sounded. But what do these sounds mean?
The modems are trying to find a common language and determine the weaknesses of the telephone channel originally meant for human speech. The telephone network exploits this fact and temporarily silences the return channel to suppress any confusing echoes of the talker's own voice. The tone also has periodic "snaps" (180° phase transitions) that aim to disable yet another type of circuit called echo canceller.
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