Asterisk on a isdn connection

hi,

target:
block anonymous calls with asterix, without the telephone ringing.

what i have:
a standard isdn connection with the needed hardware and a isdn -> analog converter for a analog phone.
a isdn card (fritz)
a pc with a pci slot to test it all

not the prettiest picture, but it will do:

as far as i understand it, asterisk needs to go in between my “wall connection” and the phone - like a firewall. is that right?

i talked to some people on irc and it looks like there are two ways

  1. capi
  2. sip (newer fritzbox needed)

lets say i want to go the capi way.
how do i connect a pc so that it sits in between my phone and the connection?
is there maybe a picture somewhere or is this a exotic setup?

someone on #asterisk was able to make me undestand.

final setup looks like this:
isdn So -> fritzbox -> phone/pc with asterisk

fritzbox will be cofigure to redirect all calls to asterisk, asterisk will then handle the call.
kill it, redirect it to the phone and so on.