A Little Modem History

Modems can be traced back to the 1950s. They were developed to transmit data to North American Air Defense via telephone lines. The first commercial modems didn't appear until 1962, with the Bell 103 protocol developed by AT&T. The Bell System 103 Series was the first modem with full-duplex transmission and Frequency Shift Keying (FSK) modulation. It was capable of transmission rates up to 300 bits per second (bps). The follow-up product, the Bell 212 Series, boosted data rates to 1200 bps (that's four times faster than the previous product) and employed improved Phase Shift Keying (PSK) modulation.

1965 brought the development of the automatic adaptive equalizer. This invention compensated for differences in signal attenuation ...

Get Online! The Book now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.