Data over normal GSM call

Fabian Olesen firewalkerx at
Mon Apr 14 04:15:01 CEST 2008

On Mon, Apr 14, 2008 at 3:33 AM, Fabian Olesen <firewalkerx at>

> On Mon, Apr 14, 2008 at 2:57 AM, Hans L <thehans at> wrote:
> >
> > The standard tones allow up to 16 values to be represented at a time,
> > so it would be like transferring data in base16 (aka hex or 4 bits at
> > a time).  According to wikipedia, the minimum length of a tone should
> > be 70ms, which would limit data transfer to roughly 56 bits/second.
> > Of course this is very slow and unusable if you are thinking in terms
> > of web browsing, but could be useful for transmitting small amounts of
> > data such as URIs or other connection information(an IP address is
> > only 32bits).  The URIs could be accessed immediately if the receiving
> > end has a simultaneous internet connection, or saved for later.
> This could actually work
> But it would require that both ends have a specialised phonestack
> (openmoko fx)
> where some kind of protocol was inplemented for listening for DTMF with a
> start and stop signal,
> where the phone would know not to send the tones into the ear piece,
> so that it would not scream into the other user's ears.
> after a little research, i came across the Goertzel algorithm (Wikipedia
link) <>


Fabian Olesen

If it moves, compile it.
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