Cellular compression will not play nicely with analog modems. (Or any lossy compression, really - this is why you have to use lossless G.711 to have any hope of

Cellular compression will not play nicely with analog modems. (Or any lossy compression, really - this is why you have to use lossless G.711 to have any hope of this working on VoIP.) Back in the days of 2G cellular, GSM had an option to have your cell phone digitally connect to an analog modem in the cell tower, and have the tower place an analog modem call on your behalf. (Very similar to how T.38 works for faxes in the VoIP world.) You'd then connect your cell phone to your laptop over RS-232, IrDA, or Bluetooth. It was called CSD ("circuit-switched data), and used 1x voice channel for 9600 bps, or 4x voice channels for 56 kbps. Needless to say your cell carrier charged quite a bit for using this capability. I don't know if there's any cell carriers left that still offer CSD calls.