Using an acoustically coupled modem over a cell phone




What can one do with it?




and more…

plus vim…


With a low enough bitrate, considerable FEC built into the protocol, and robust mechanisms for retransmit it’s surely possible to work around the compression inherent to cellular voice.


Back in the days of dialup, I bought one of these at COMDEX.

It never worked very well and I went back to taking the phone apart and hooking up my modem to the innards with alligator clips in those few cases when the phone did not have a data jack and was wired to the wall.


That brings back memories…

Use to use that and a palm pilot in the 90’s to dial up my favorite boards and shell accounts.

Hell, the world’s first smartphone was born out of these:


hmm, I wonder if my bbs door botnet is still around somewheres…


Palm was ahead of their time. They were making the transition from the 68K based DragonBall processor to the ARM when the PDA market went away.


I remember distinctively using my StarTac in 2000 to check my email and look at some websites. Wow that was an expensive phone bill. 400+ dollars for that month.


That was part of the problem back then. No free or low cost data. The other was slow 2G or even 1G data rates.


That reminds me.

I once worked on a project to build an emulator to run apps written for Palm OS on foreign hardware without requiring the ROMs from a Palm or compatible PDA.

The idea was to run Palm apps on Pocket PC devices and sell the company to Microsoft for a small fortune sort of like what Mark Cuban did with The initial project code name of TestPilot was changed to OutCuban to make it more obscure.

We got far enough along to run the then popular games like Vexed! and Bejeweled. My favorite was Freewalk though it was rather slow.

We folded the company when the PDA market started going away and when we discovered that a large number of apps wrote directly to the display buffer instead of using the OS interfaces, making our job that much harder.


Based on limited information and some personal experience:

The cellular network will detect the modem negotiation tones and either switch to a G.711 u-law codec (same bandwidth as your POTS line) or “pretend” to be the other modem, push the bytes across the network, and then re-modulate them on the other side.


Interesting. Surprised the cell providers were that courteous.

Back in the earliest days of supporting FiOS I remember customers calling us rather upset that they couldn’t dial in to AOL, their office’s modem pool, etc. Turns out that the PON standard used some compression on POTS that rendered modems useless past standard fax machine baud rates.


Yeah, I suspect it wasn’t straight G.711 (u-law), which is/was used to carry voice around on the PSTN digital trunks. MoDems are strange, mystical beasts, which I’m going to be studying in my Comm Systems I class this semester. Trig and Calculus are fun! barf


Calculus was enjoyable for me until we hit differential equations. We were later told that we were taught DiffEq so that we can appreciate “don’t do that!” when taught better techniques.


I got my best grades in DiffEq. I took it over the summer and just “got it”, which was a start contrast to my performance in Calc I/II/III.