• Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

Chapter 17. How a Modem (Really) Works > A Little Modem History

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 rates and smearing data symbols, and was necessary for creating the V.22bis standard at 2400 bps. This, along with the adaptive echo canceller, paved the way for higher data rates: 9.6 kilobits per second (Kbps) (1984), 14.4 Kbps (1991), 28.8 Kbps (1994), and 33.6 Kbps (1996).


PREVIEW

                                                                          

Not a subscriber?

Start A Free Trial


  
  • Creative Edge
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint