The sound was useful. One of my modems in the 1990s would falter about 1 out of 8 times. When it faltered, it would never connect and never hang up. Without knowing or learning any of the technical information in the OP, I learned to distinguish the sound of a faltering attempt to connect from the sound of a normal one. If I were not able to hear the "tones"/sounds, the only way I would have been able to detect a faltering attempt is when the attempt lasted longer than successful attempts do. So, being able to hear the sound saved me time: I was able to detect a faltering attempt faster. (About 10 seconds faster. My response was to hang up and redial.)
In other words, having the modem duplicate the lines' "tones"/sounds over a speaker was a nice hack on the natural human ability to distinguish between different sets of complex patterns.
A similar hack: there is a blind programmer named Karl Dahlke who pipes the character stream being sent to his Linux console through his PC speaker. Even though it probably sounds like radio static or a cacophony to the untutored ear, he has been able to learn to distinguish certain patterns quickly without having to wait for his text-to-speech software to read him any of what is on the console.
ADDED. The "blinking lights" on the front panels of early computers and mini-computers is another example. I understand that computer operators learned to extract a lot of relevant information from the row of lights on the front of the computer that formed a binary representation of the contents of the program counter.
I understand that computer operators learned to extract a lot of relevant information from the row of lights on the front of the computer that formed a binary representation of the contents of the program counter.
Parenthetically, these "out of band" debugging cues still work. Try holding an AM radio next to your PC's motherboard. :)
This was occasionally useful for debugging before CPU clock frequencies started to look less like AM radio and more like microwave ovens...
In other words, having the modem duplicate the lines' "tones"/sounds over a speaker was a nice hack on the natural human ability to distinguish between different sets of complex patterns.
A similar hack: there is a blind programmer named Karl Dahlke who pipes the character stream being sent to his Linux console through his PC speaker. Even though it probably sounds like radio static or a cacophony to the untutored ear, he has been able to learn to distinguish certain patterns quickly without having to wait for his text-to-speech software to read him any of what is on the console.
ADDED. The "blinking lights" on the front panels of early computers and mini-computers is another example. I understand that computer operators learned to extract a lot of relevant information from the row of lights on the front of the computer that formed a binary representation of the contents of the program counter.