
Build your own dial up ISP in 2019 - rahuldottech
https://dogemicrosystems.ca/wiki/Dial_up_server
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skissane
I thought before the idea of modem-over-VoIP would be cool to have a BBS which
was more retro than just a telnet BBS could be.

(At my house, my only options are VoIP and cellular. POTS service has been
shut down.)

I wonder how well modems work over VoIP though? My understanding is that the
voice-oriented compression causes problems (although you can turn that off by
using G.711), but the bigger issue is the unreliable timing of most IP
connections upsets the modem and it keeps on disconnecting.

ITU V.150.1 (aka V.MOIP) is supposed to fix that but I don't know think many
VoIP providers implement it.

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icedchai
I've done 2400 baud and lower over VOIP. 9600+ gets bit unstable.

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anfractuosity
Naive question, I've not used VOIP before, is the modem, implemented entirely
in software to achieve this?

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icedchai
I use a hardware modem (USB modem actually) attached to a hardware VOIP analog
telephone adapter. I am not familiar with software VOIP modems but hopefully
someone else can chime in if it's possible.

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ktpsns
Amazing. I also plan to build that.

I wonder if telephone providers have some sort of recognition to detect people
using (abusing?) a free call plan for transfering data. Certainly, if your
"call" takes several days, that may violate some TOS.

(The use case I have in mind is to save money by using cheap prepaid SIM cards
without an internet plan. It is purely for interest/proof of concept, not for
scamming...)

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tiernano
i know in Ireland, most of our Unlimited providers have a limit of 45000 min a
month... which is grand, given there are only 44640 min in a normal 31 day
month... but GSM is a lot more limited in bandwidth than standard POTS: old
GSM Modems would top out at 9.6kbps, with some having a 14.4kbps option... it
wasnt till GPRS that you got faster speeds (packet switched, not Modem).

~~~
jsjohnst
> it wasnt till GPRS that you got faster speeds

Forgot to mention, GPRS uses the same time slots as voice calls do over GSM.
Each time slot is still limited to about 9.6k useable data rate as with using
a modem, but GPRS allows bonding to use more than one time slot. As such,
using three time slots would get you 28.8k, using six gets you 57.6k, etc.

~~~
tiernano
both comments are very handy to know! thanks. i remember trying to get
internet access on my Nokia 7650 back in the day, and been given HSDCA and
GPRS as options... larger downloads usually worked out cheaper on HSDCA (it
was charged per min, no bandwidth limit, bar the standard limits) but GPRS
worked out handier for "browsing" which, back then, was not standard either...
big difference between now and then...

~~~
jsjohnst
Back when I had an ISP in the mid 90s, I felt like I was king of the world as
I had a T1 going to my place (as I only had to pay for the local loop,
bandwidth was “free” by owning the ISP). My dream back then was to have those
speeds everywhere I went. Fast forward 25 years and my _watch_ can get 20x
that speed even in a random rural area.

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jdmoreira
Unrelated but can some one tell me what is the "portable" computer in the
picture?
[https://dogemicrosystems.ca/mywiki/images/3/3c/DIY_dial_up_I...](https://dogemicrosystems.ca/mywiki/images/3/3c/DIY_dial_up_ISP.jpg)

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TomNomNom
That looks to be an INET Spectra of some kind. Possibly an 8243-1 based on a
few searches.

~~~
jdmoreira
Thank you!

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non-entity
Oh haha, I remember finding this a couple months back when I was discussing
with a colleague, an old serial modem I have. I was wondering how difficult it
would be to simulate a modem connection between the terminal and a PC as
opposed to a direct serial line between the two. Now that I found this again,
I might have to try it out.

~~~
tenebrisalietum
Many "Winmodems" in the 90's and beyond were little more than soundcards
connected to an RJ-11. Modulation/demodualtion was done in software, and this
was in the sub-1GHz days of PCs. So this was actually not uncommon, but of
course binary only.

There were some Linux projects to do this in a generic way - basically
generate the required tones over the audio output and interpret tones over an
audio input - and implement the various ITU V-series standards (though some of
them were patented and could not be implemented, like V.92 for 56k).

There's another one other than iaxmodem
([https://stackoverflow.com/questions/3069945/open-source-
soft...](https://stackoverflow.com/questions/3069945/open-source-soft-modem-
that-runs-on-linux)) but I can't remember what it is.

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msla
"First, catch your rabbit." \- Old recipe for rabbit stew.

This lists a real serial modem as a prerequisite, and those are kinda getting
to be collectors' items. Is it feasible to build a modem out of a Raspberry Pi
Zero or an Arduino? You'd need to hook the phone line to the GPIO pins, do the
ADC and DAC stuff in software, implement the V.22 protocol in software, and
also implement the Hayes Smartmodem stuff in software, meaning this is one of
the few times a Hacker News reader would have occasion to implement the Hayes
Code. Is there any show-stopping problem I'm not seeing? Massive electrical
incompatibility?

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tyfon
Quite cool :)

I have my trusty old USR Courier and USR Sportster 14400 in a box. But I'm a
bit more tempted to try and get pcboard running again using some of this
setup. I don't have a landline in my house, only fiber so the asterisk option
would be the way to go.

I also have disk images of my ms dos 6.22 floppies and PCBoard 15.22. I also
have desqview for multinodes but I remember it was a PITA to get it running.

Now I just need an old 486 that is still running, my oldest running machine
has dual pentium pro cpus and it doesn't behave all that nice with ms dos.

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dang
[https://news.ycombinator.com/item?id=19135434](https://news.ycombinator.com/item?id=19135434)

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ngcc_hk
Interesting. Still thinking back local setup a cell during protest to avoid
interception ... guess phone call affected.

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tempodox
Dial disks have gone extinct, so no more dial-up in the 21st century.

