audio link Re: Peer Discovery

Robert Michel openmoko at
Mon Dec 11 18:38:09 CET 2006

Salve Ole!

On Mon, 11 Dec 2006, Ole Tange wrote:

> On 12/11/06, Richard Franks <spontificus at> wrote:
> >On 12/8/06, Colin Curtin <colin at> wrote:
> >> > Put two Neos in a room with no cell service - can they find each other?
> >> >  Even with service, if nobody punches in 'codes' on each?
> >> >
> >> Oh, if only it had bluetooth.
> >
> >If the speaker could output frequencies above ~22kHz, and the
> >microphone sampling rate could be tweaked high enough.. you may be
> >able to build a primative close-range comm protocol with that?
> Well, I still remember modems that used acoustic couplers. So it might
> be a solution to just use old modem technology (300 baud anyone?) for
> transmitting small files from Neo to Neo.

There are several audio modulations for datatransmission for using
radio (packet radio) they should be usable for speaker2mic communication
as well (radio amateur stuff). Plugging a PMR handheld would be also
fine - this data transmission via audio could also used inside
internetcaffe - put your Neo1973 close to a headsest or plug 
audio in/out to your Neo1973 and use a original installed internet
telefonie client or an own data transmission client to use audio
for an internet connection.
I also thougth about if up to 1200 baud could be reached to use
via GSM in case that no data-calls would be possible. 
Use your audio tape for backups....

But back to 300 baud...
> > 10 bonus points if it sounds like R2D2.
efficient data transmission via audio mustn't sound well
for the user - DTMF for transmitting your phonenumber 
would be acceptable, but the other modulations?

To beem your virtual business card via audio it would be
nice when the data transmission would be encoded into
a non uggly modification of a voice output:

"I'm beaming you now my virtual buseness card - complete"
So that every user will hear how long this transmission
is and what is going on.

Such a solution could be also run on other smartphones with
java - send and receive business cards and more without
Bluetooth or IRDA nor cable nor online connections.


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