I have two 3845 routers that are being used as voice gateways The IOS is version 12.4(13f). I am connecting them to an Avaya PBX through T1 lines provisioned for ISDN. I'm using MGCP and CUCM 6. The module in slot 0 is listed as a NM-4VWIC-MBRD. When I connect the devices through either port on a VWIC-2MFT-T1 in subunit 0 I can make everything work just fine. The module in slot 3 is an NM-HDV2-2PORT-T1. In subunit 1 there is an NM-HDV2-ONBOARD-T1-2PORT module listed. On the router, I set up the T1 controller for that port, set up the voice port, and set up the serial port the same as the ports in slot 0. On CUCM I set up everything just like the working ports. However, if I make a phone call and use the lines in slot 3, the phone rings, I get called ID, but when I answer I get no audio. The person making the call also hears no audio. They don't even hear a ringback.