asterisk users - Jun 2005 - Fax + Fritz + Capi + detection

Hello

I'm newbie in asterisk and i have a "AVM Audiovisuelles MKTG &
Computer System GmbH Fritz!PCI v2.0 ISDN (rev 02)" with CAPI Driver.
I would like install fax detection, but i don't know if i should use 
NVBackground detect; or CapiAnswerFAx; or other.
I don't understantd operation of fax.

Tx

ps: sorry for English i'm french