An update to my dial-up ISP project. I got a two node modem pool working a PCI card to add more serial ports. Instead of my Verizon line, I patched these modems into my PBX running asterisk with a Grandstream ATA with 4 internal lines. The PBX takes incoming calls from a new number and uses a basic hunt group to connect to caller to the next free line.

Got a dialup modem? Feel free to give a call and let me know what OS you are using, how it goes. Details at

Don't know how I had so many missing/incorrect words in the last toot, but I think it still makes enough sense.

Previous thread on the project is here,

@alexbuzzbee You could always get a voip line or a magic jack or something if you truly wanted to fall down this rabbit hole. Your life will be prone to latency issues, happy modem sounds, and hundreds of feet of silver phone wire. You may or may not one day think it is a good idea to buy a fax machine or answering machine. You'll wake up in a cold sweat wondering where your punchdown tool is.

@Famicoman Plugging a USB modem into a magicjack is a hilarious image. Just two USB phone jack dangly things hanging out the back of the same computer plugged into each other, converting bytestreams into audio and then back into bytestreams.

@alexbuzzbee I love that mental image. I actually might do it at some point because it seems so funny.

@Famicoman Have you been able to get the modems to talk to each other through SIP? I played a lot with that and it took some doing. I have grandstream HT702's hooked to my Panasonic PBX. About 300 was all I could do reliably to the SDF dial in number.

@junkman Yeah I've got speeds of 33.6kbps with few issues. I haven't tested any POTS lines, it is all VoIP. I've been doing Verizon voip to and my friend has been testing Google Voice to and we usually get something close to that. I think all I did on the ATA was make sure to prefer G.711 and turn off any echo cancellation. It might just be luck that there isn't much lag in the connection.

@junkman It's down right now but the dogemicrosystems guide has tips for ATA configuration,

I think that's really the only bit of that page I used as I am running Win Server right now, though I do want to switch things over to Linux at some point.

I'm using a Granstream HT504 myself so I imagine it isn't too big a jump for a 7XX model.

Sign in to participate in the conversation
Mastodon @ SDF

"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko