The Bell 101 Data Set was the first commercial modem for computers, released by AT&T Corporation in 1958 for use by SAGE, and made commercially available in 1959, shortly after AT&T's Bell Labs announced their 110 baud modulation frequencies.
[1][2] The Bell 101 allowed digital data to be transmitted over regular unconditioned telephone lines at a speed of 110 bits per second.
The Bell 101 modem used audio frequency-shift keying to encode data.
Different pairs of audio frequencies were used by each station:[3] Bell 101 modems are no longer in use and were quickly replaced by its successor the Bell 103 modem.
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