Love this super geeky post about what the sounds mean during a modem handshake.

The sound of the dialup, pictured

“As many already know, what you’re hearing is often called a handshake, the start of a telephone conversation between two modems. The modems are trying to find a common language and determine the weaknesses of the telephone channel originally meant for human speech. Below is a spectrogram of the handshake audio. I’ve labeled some signals according to which party transmitted them, and also put a concise explanation…

Remember when a 57K modem was the shit??