Why Did Dial-Up Modems Make So Much Noise?
Screeeech . . . hisss . . . squaawk. These are familiar sounds to anyone who’s ever used dial-up internet or called BBSes. It seemed especially noisy late at night. Have you ever wondered why all that noise was necessary? And did you know you could have muted your noisy modem?
Benj Edwards Dale Heatherington Hayes Microcomputer Products Anderson Jacobson Acoustic Modem Hayes Stack Smartmodem Hayes Microcomputer
Source: howtogeek.com