I understand that modems used the telephone line to transmit and decode sound into data, but I don’t understand why that noise everyone remembers needed to happen. You didn’t hear sound when you were loading a web page even though sound was being decoded by you modem… what was the purpose for it on start-up?
Edit: Autocorrect typo
In: Technology
There were many standardised signals in the first part of the connection. By the time you’re sending particular data, it’s mostly noise to the human ear (which the modem usually silenced, but you could turn it on if you wanted – it just sounds like Sssssshhshshhshshshshhshshshshshhshs).
But the first parts are tones to indicate “I’m a computer, not a person” (to stop faxes and automated systems getting confused by not having a voice), then a response to say the same from the other end, then a serious of small data blips, then a long wavering/diminishing sound as the two sides negotiated speeds and discovered whether there was any interference on certain frequencies. Then it’s mostly static but sometimes you would hear a sudden sssshshshshhshsNNNNNNNNNEEEENNNNNNNNNAAAANNNNNNOOOONAAAAAAshshsshs – that usually indicated that the two sides had lost communication briefly, and they letting the other side know so they could both start again (or downgrade the speed slightly next time).
Growing up with a ZX Spectrum gave you a fine ear for what was happening in an audio-based data stream…
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