No sure what broadband has to do with it. Unless you mean an IP phone? If so post a NEW question with more information about your VoIP setup.
The telephone circuit, although on the same pair, uses different frequencies to the ADSL (Broadband). That is the function of the micro filters - to split the two services.
The usual way to run a fax and phone on the same number is to get the fax to wait for a specific number or rings before it answers. One can usually set different ring tones to the fax and phone so they sound different. None of this has anything to do with broadband however.
t, February 2008
