Change number of rings before IVR

I have my Trixbox system set up to forward calls to different IVRs depending on which port it is coming in on. The problem I’m having is that I want the line to ring about 4 times before going to the IVR, but currently the IVR picks up right away. How can I change the amount of time the line rings before going to the IVR? I know I could use a ring group, but I’m not using IP phones that are connected to my Trixbox.