Readers of a certain age will remember these waveforms – not by looking at them, but by sound. This is what data looked like as transmitted by a 4800-baud modem.
It’s kind of funny for someone like me, who’s used to audio recording, to skim over the Folkscanomy Electronics Article this came from – it’s full of terms like “low-pass filter” and “noise gate” which are things you use in messing with, like, how a bass guitar sounds. But this… this was how computers talked to each other in the pre-web days of the internet. This wasn’t even for a phone – it was for packet radio.