Missed call communication protocol

Richard Bennett richard.bennett at skynet.be
Fri Feb 9 01:53:02 CET 2007

On Thursday 08 February 2007 15:06, Alexandre Ghisoli wrote:
> I was working on a project, maybe 15 years ago, where we developped a
> "modem" to transfer data :
> 1/ during setup, for free
> 2/ during the blanks of a conversation (approx 80% of the time, because
> only one speaks at time, so you got a free 64kbps channel :))
> This takes not very long until telco notice the D channel trafic, and
> since then, they charge for alerting, even if no answer (maybe 10% of
> unanswered call) to cover this trafic costs.
I can't say I have ever seen these costs mentioned anywhere for wholesale 
termination, but they might be mentioned in the T&C, and only applied if they 
detect a strangely high percentage of bad calls.

Actually, I would be quite happy if they opened-up this mechanism, and did 
charge something (like 10% of the CPM) for it for those end-users who wanted 
the service. it would allow seeing extended user identification for people 
not yet in your contacts book, and quick saving of contacts without typing 
their names. (amongst a whole range of other uses)  

> So, second part was to cut additional messages (SETUP DISPLAY) between
> network (aka roaming or international call). This need a more deeper
> test, but IMOO, this *could* be working on some networks, and probably
> not on some other.
> Now, about GSM networks and Gateways, I really dont know if this is a
> 1:1 passtrough ..
I think some testing would be usefull, although I it will probably not work 
reliably across networks... I still have a 4E1 Didgium board lying around 
somewhere begging for something usefull to be done with it...


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