[GreenKeys] "Strange Tones" on M32 Modem

[Buck Kidd III]

Try Googling, "Bell 103 protocol."


 From Wikipedia:

The *Bell 103 modem* was the first commercial modem for computers, 
released by AT&T in 1962. It allowed digital data to be transmitted over 
regular telephone lines at a speed of 300 bits per second.


The Bell 103 modem used audio frequency-shift keying to encode data. 
Different pairs of audio frequencies were used by each station:

    *


    * The *originating* station used a mark tone of 1,270 Hz and a space
      tone of 1,070 Hz.
    *

    * The *answering* station used a mark tone of 2,225 Hz and a space
      tone of 2,025 Hz.


Although original Bell 103 modems are no longer in common use, this 
encoding scheme is referred to generically as "Bell 103 modulation", and 
any device employing it as "Bell 103-compatible" or "a Bell 103 modem".