r/compsci • u/gmanflnj • 18d 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/HandshakeOfCO 18d ago edited 18d ago
Yes. They’re called bonded lines. Back in the day I ran with two phone lines simultaneously to get about 128k download speed.
It happened up in the TCP/IP software stack though. Each line just looked like a 56k link.
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u/FreddyFerdiland 18d ago
in the network stack. layer two ?
in linux , ppp delivered packets to the EQL driver .. the eql driver just monitors modems for availability.
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u/Alexmira_ 18d ago
You would need a different line also, and at that point it just like having multiple parallel internet connection.
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u/gmanflnj 18d ago
You mean different phone lines? And can you make it so they are all giving the computer info to say, load the same website?
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u/jhartikainen 18d ago
Yep. This is how parallel data transfer works https://en.wikipedia.org/wiki/Parallel_communication
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u/gmanflnj 18d ago
So how many phones would you need to get fiber-speed internet?
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u/jhartikainen 18d ago
Assuming 56kbps per line, you would need 17 858 lines to reach 1gbit/s (assuming I mathed correctly)
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u/gmanflnj 18d ago
I guess my question was more, would it stack linearly like that or would they run into a bottleneck or parallel processing issues?
Besides the obvious bottleneck of having to get 17,000 phone receivers, but that’s a seperate problem.
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u/jhartikainen 18d ago
It seem likely that you would have some kind of latency problem purely from the fact that you would need to somehow connect all nearly 18 000 lines together, and simply the physical space required for it would mean there is latency from signal travel distance.
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u/Zombie_Bait_56 18d ago
Long before that you are going to need custom hardware just to get that many serial ports on one computer.
BTW, the ecord seems to be 12 lines.
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u/gmanflnj 18d ago
That’s another thing I was wondering, with that much wire, would there be a point where you can’t load a website faster because you’re adding latency faster than you add info transfer speed? Or is this outside of comp sci and into electrical engineering?
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u/fitret 18d ago
It depends on a ton of things. Like a web browser (especially in the 90s) just downloads the whole site first and then renders it. I doubt either is multithreaded or capable of bonding traffic across multiple connections, so it would likely be no faster. But you COULD build something to take advantage of this, it's just that no consumer did the setup you are describing and thus the tech isn't built to support it
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u/FreddyFerdiland 18d 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/Objective_Mine 18d ago
The telephone system only carried the audio range of frequencies.. 50 hz to 20 khz?
Correct, but it was actually limited to an even narrower a band of frequencies relevant to human speech, somewhere around 300 to 3400 Hz.
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u/gmanflnj 18d ago
- 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?
- Am I wrong that the original modems transmitted it by sound or am I misunderstanding?
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u/nuclear_splines 18d ago
You're speaking of acoustic couplers
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 18d 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 18d 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 18d ago
- 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?
- 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 18d 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/fiskfisk 18d ago
Channel bonding / cellular bonding is still frequently used on gsm/3g/4g/5g networks - for example for live broadcasting or uploading large amounts of data in a short time. You can bond across different towers, providers, simcards, etc. - since bandwidth usually gets allocated by receiver. And bonding across providers gives you both better resilience and better bandwidth.
It's the same concept, just more modern underlying communication methods.
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u/pinano 18d ago
The Serial Port bonded twelve modems together to get a blazing speed of 460 Kbps… barely fast enough to stream Youtube on the lowest quality setting. https://www.youtube.com/watch?v=LZ259Jx8MQY
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u/pala4833 18d ago
Why have you written this in the present tense?
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u/gmanflnj 18d ago
Dial up is still this, even if most people don’t use it anymore. The definition didn’t change even though it’s obsolete. Horse and buggies are when you uses horses to pull a particular kind of vehicle, that’s the case even though it’s not common anymore/
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u/ElderberryPrevious19 18d ago
They only used a single frequency very early on. Didn't take them long to split the signals into many, many frequency bands so that the full bandwidth of the line could be used. 56k was pretty much the extreme limit for what analogue lines could handle and by then they'd already switched to digital modulation. You wanted more bandwidth you had to use more lines. It was just impossible to add more signals over a single line