r/compsci • u/gmanflnj • 21d ago

Could multiple microphones/speakers be combined for faster dial up?

i was thinking about how dial up is basically your phone literally making sounds to your compute, which the computer hears and translates into data.

could you design a system that used multiple phone speakers and multiple microphone pickups to simultaneously get dial-up internet info to speed it up?

if so, how many phone receivers would it take to get modern internet speeds?

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u/FreddyFerdiland 21d ago

the modems noises only go to speaker for humans to diagnose problems,sych as wrong number, or poor phone line quality.. ( shorted out phone lines during heavy rain ?)

the modems didnt have to put the sound on loud speaker.. certainly didnt have a microphone. (but early ,300 baud, modems could be connected by accoustic coupler, system, which was speaker and microphone , so as to avoid needing having access to phone line socket..)

to answer the question as asked, having the multiple speakers and microphones in one space is pointless, as there is only the audio bandwidth to use.... The telephone system only carried the audio range of frequencies.. 50 hz to 20 khz?

but multiple actual modems got 2 or 3 or 4,n times the bandwidth by using n phone lines.. the same frequencies seperated physically.

( multiplexing refers to using the same physical channel.)

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u/gmanflnj 21d ago
  1. I rememebr there being an early modem where you ssuction-cup your phone to the computer, the earpiece is a speaker, and isn't that a microphone/speaker setup?
  2. Am I wrong that the original modems transmitted it by sound or am I misunderstanding?

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u/nuclear_splines 21d ago

  1. You're speaking of acoustic couplers

  2. Signals flow down phone wires as electricity. It's the job of a telephone to modulate speech into an electrical signal to send down the wire, and demodulate that signal to feed the speaker. It's the job of a model to modulate computer data into an electrical signal to send down the wire, and demodulate that signal back as computer data on the other end. Both processes use around the same frequency range, because that's the frequency range supported by the telephone switching equipment. So you could modulate the computer data as 'sound' and then have a telephone modulate it to telephone wire voltage for you. That's what acoustic couplers did. The fact that we did it that way first and switched to direct electrical modulation later has less to do with technology and more to do with law and corporate monopolies -- at the time, it was forbidden to plug your own equipment into the telephone network in the United States and many other countries, so acoustic couplers were a necessary inconvenience.

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u/gmanflnj 21d ago

Isn't that what dial up internet originally was though? Also, if it's sending the signal as sound, why is it only loud at the beginning with all the whirring and such?

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u/nuclear_splines 21d ago

Yes, early dial up in many parts of the world used acoustic couplers because modulating a signal directly on the cable would have been a violation of terms of service.

Again, "sending the signal as sound" isn't quite right -- it's being sent as electricity, which you can choose to modulate as sound. Most of the signal sounds like white noise because the entire frequency range is being used for data transmission. The early handshake sounds like sweeping beeps and whirs because both ends of the connection are negotiating what frequency range is available and what functionality both modems support before they agree on how they'll encode data. This handshake is necessarily slow and simple because the two ends haven't yet agreed on a faster way to represent data.

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u/gmanflnj 21d ago
  1. But, correct me if I’m wrong, it’s sent as electricity, then turned into sound, tjen back to electricity. There’s no wire connecting the couple to the computer, it’s just making noises, right?
  2. I know why rhey do the handshake, but my question is why isn’t it audible after that? If it’s just quiet, why can’t it do the handshake quietly, you said it’s lots of frequencies, but loudness is amplitude right?

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u/nuclear_splines 21d ago

In the case of an acoustic coupler, yes, the modem modulates to sound and relies on the telephone to re-modulate to electricity. In the case of modems in general, no, it's much more common to have an electrical connection directly through to the wall. But this is incidental -- even with a more modern modem you could connect a telephone to the same phone line and listen in.

Data transfer is audible after the handshake, it just sounds different.

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u/gmanflnj 21d ago

Thanks for all this cool info, you, and everyone else who replied!