What does a valid FAX number look like?

There are several formats you can use:

Canonical Format (+49 9131 85 28732)

This format is called canonical because it is easily understood around the world, in most cases it suffices to prepend the international dialing code and that's it (e.g. in Germany one would prepend 00). The FAX server knows about canonical numbers. It will detect any non-international calls --- like +49 9131 85 28732, which really is an internal university call and it just needs to dial 28732 --- and dial the right number.

NOTE: Most Mail User Agents will treat a number like +49 9131 85 28732 as four different email addresses, as the ` ' (Space) is taken as a delimiter--- thus, don't use spaces, write the FAX number like this:

+49.9131.85-28732 or +4991318528732 or +49-9131-8528732 or ...

Internal Call Format (x8733)

This format is called internal call format because it tells the FAX server that you want to send a facsimile to another university number --- i.e. it does not have to get an outside line.

Local Call Format (39 388)

This is the format for doing local calls, i.e. within the same area (like within the Erlangen 09131 area).

Long Distance Call Format (09131 39388)

This is the format for doing long distance calls within the same country (i.e. within Germany).

International Call Format (0049 9131 39388)

This is the format to place an international call (e.g. to the US, UK, or any country). Alternatively you could have used the canonical format instead (saves one digit, wow ...)

The FAX server understands all of the above formats. It knows when to strip leading digits/characters, and it also knows how to reach an outside line. Thus, you don't have to worry about those things.