Modem
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Tomlinson invented email in 1972.
Digital modems developed from the need to transmit data for North American air defense during the 1950s. Modems were used to communicate data over the public switched telephone network or PSTN. Analog telephone circuits can only transmit signals that are within the frequency range of voice communication. A modem sends and recieves data between two computers. Modem stands for modulate/demodulate.

In 1962, the first commercial modem was manufactured - the Bell 103 by AT&T. The Bell 103 was also the first modem with full-duplex transmission, frequency-shift keying or FSK, and had a speed of 300 bits per second or 300 bauds.

The 56K modem was invented by Dr. Brent Townshend in 1996.