GSM data call and GSM fax

Multi numbering

If you want to receive data and/or fax via GSM, you must get and use the incoming numbers  provided by your GSM network. You will thus have separate incoming numbers for Voice (your  current cellphone number), Data  9600 baud, Data  2400 baud, and Fax  9600 baud.

Someone sending you data or fax will thus have to dial one of these incoming numbers to do  so. To send you a fax via GSM, they must thus use your incoming fax number etc.

The reason for this additional numbering that not all the analogue fixed line  exchanges/switches can process and route the digital data that the digitally based GSM  networks and cellphones use. 

Single numbering

Somel GSM networks offers single numbering. Then you will have one number  for all different kind of bearers like in a landline based ISDN application. The kind of the  bearer is digital coded. Mostly it is not needed in industrial mashine to mashine  communication. Single numbering can make trouble if you have designed your application  local  based on multi numbering and your client is supported by GSM operators that  offers single numbering only.