CSD calls from Neo Freerunner

[joerg Reisenweber]

On Tue 21 January 2014 15:42:20 Al Johnson wrote:
> On Monday 20 January 2014 07:31:55 Michael Spacefalcon wrote:
> > For those who don't know what CSD is:
> > 
> > http://en.wikipedia.org/wiki/Circuit_Switched_Data
> 
> [snip test call logs]
> 
> > CSD calls may be placed from a GSM mobile either to a land line or to
> > another mobile.  (I don't know if it's possible to establish a CSD
> > connection from a land line to a mobile.)
> 
> It's possible to establish the connection from land line to mobile, with
> both analogue and ISDN landlines. I used to use it for remote access to
> condition monitoring systems. You should be able to send and receive faxes
> too. It does need carrier support though.



For landline to mobile you need to signal to carrier that the OTA connection 
shall not use GSM-codec for voice but rather establish a 9k6 data connection.
From ISDN you can set the "data" service class flag, from analog landline there 
is no such flag. So usually a dedicated telephone number for inbound CSD-
datacalls is mandatory and carriers rarely support this nowadays, anyway you 
have to ask your carrier to provide such number for your mobile.
IIRC there's another method where mobile switches type of a connection on the 
fly, so you'd initiate a voice call from landline to mobile and then mobile 
switches type to datacall. Can't remember what the according AT-commands been 
to accomplish that.

cheers
jOERG
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