The famous
Bell 103A dataset standard was also introduced by AT&T in 1962. It provided full-duplex service at 300 bit/s over normal phone lines.
Frequency-shift keying was used, with the call originator transmitting at 1,070 or 1,270
Hz
and the answering modem transmitting at 2,025 or 2,225 Hz. The readily
available 103A2 gave an important boost to the use of remote low-speed
terminals such as the
Teletype Model 33 ASR and KSR, and the
IBM 2741. AT&T reduced modem costs by introducing the originate-only 113D and the answer-only 113B/C modems.
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