More specifically, how does an ME know that an incoming call is a fax call?
The example at the end of the AT Commands Guide shows a +FCON response after ATA - but that doesn’t happen if I just call from an ordinary fax machine on an ordinary phone line.
If the call comes from an ordinary fax machine on an ordinary phone line, it is indistinguishable from a voice call.
So how does one place a fax call to a GSM ME?
Does it have to go via some specific interworking facility in the network?
Does the SIM have to have a specific Fax number allocated (as for Data calls)?