Data over normal GSM call

Tilman Baumann tilman at
Tue Apr 8 17:16:23 CEST 2008

Mikko Rauhala wrote:
> On ti, 2008-04-08 at 10:22 -0400, Dan Staley wrote:
>> I have plenty of cell minutes (not to mention free calls between certain
>> numbers...) but I dont want to pay for a data I figure if I
>> wanted to, I could just have my phone call my computer and transfer data
>> over the line.
> There has been talk of it (especially in connection to encrypted
> phonecalls). The archives have a lot of it.
> To summarize, you can't transfer very useful amounts of data over a GSM
> voice call since we can't bypass the GSM chip's audio codec for those.
> Obviously you can get some data through, but the highest anyone's gone
> was IIRC ~1k using some kind of funky phonetic coding, but I believe
> there was no exact reference to this either, let alone code (which would
> be rather complex).

Maybe CSD is billed like a voice call. I never used it, but i don't 
remember any special charges for that.

The Wikipedia article about CSD has some hints about running voice 
modems via GSM too.


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