I am trying to connect an Option 11C running Succession 4.0 (no signalling server attached) to an Option 81C running Succession 3.0 (no signalling server attached)over a point-to-point T1 using PRI. I am able to get the loop to enable, and the DCH to establish, but all channels stay in a MBUSY state and call attempts receive a fast busy. There are no alarms. Is anyone aware of any compatibility issues with 4.0?