Outgoing only analog trunk

I have an Asterisk PBX that uses VoIP. I would like to use one analog telephone line as a backup for times when my IP fails (using TDM400). The analog line I have is used for other purposes, and should be answered by humans. I would like to connect the Asterisk to it, so it would use it for outgoing calls only (that is just when the IP fails).
Is there a way to configure the Asterisk so that it will not answer the ringing on the analog lines, and will only use it to dial out calls?

Yeah all you have to do is not do anything with the incoming call, but why wouldnt you want the call to be answered? You can assign the fxo port to the line group, that way it will use the fxo.