Missed call communication protocol

[Richard Bennett]

On Wednesday 07 February 2007 13:42, Florent THIERY wrote:
> I like it too, but technically, it's a hidden channel (illegal...)
Hi,
I wonder if it is illegal, it is used quite a lot allready:

Callback has been used for years to circumvent collecting charges: ring a 
number that returns a 'busy' signal, the system then calls back the CLI it 
detected.
Ringback is used widely by carriers: Call someone who's number is busy, the 
carrier will offer to connect you when the other party is free, using the CLI 
they detected from your failed call.
Progress messages: Carriers will routinely playback audio messages without 
actually opening the line, like 'The person you are trying to call is out of 
reach...' .
Missed Call display on a mobile. By displaying the message 'you have 4 missed 
calls', and then making it possible to ring these people back mobiles are 
already using MCP in a limited way.

As far as I see there is nothing illegal going on. When SMSses were first 
introduced they were free too, it was only later carriers started charging 
for them. Carriers could also start charging for missed calls, if people 
started using MCP in a big way, but by that time openmoko will have wifi ;o)

Richard