Numbers and routing
Numbering plan
A numbering plan sets the structure of a country's phone numbers and the use of each range; in France, it is managed by the regulator, Arcep.
In France, a number has ten digits. The first two show the category: 01 to 05 for geographic numbers, 06 and 07 for mobiles, 08 for special numbers, 09 for non-geographic numbers. The plan also defines short numbers and the conditions under which each range is allocated to operators.
Why it matters for fax
The plan is what tells you, just by reading a number, whether it can be a fax: fax machines are connected to fixed numbers, geographic or not. A mobile or special number has practically no chance of reaching a fax machine.