See the attached drawing.When connecting two 4wire ports together, we need to swap the INs and OUTs on one side of the CAT5/6 cable.  We need to flip the BLUE and the GREEN pairs on one side of the cable.  Otherwise, we'd be sending and input to an input, rather than an input to an output. Only use a straight through CAT patch cable when going from a Matrix to a Panel or other endpoint device, like a HelixNet module, BS210 basestation or FSII "Classic" base, etc. (The Newer Base II has a software turnaround for this)When you need to connect any of the end point devices' 4wire ports, you will require the AUDIO CROSS OVER CABLE. 
Here is the pin out for the RJ45 4wire port on the base station or module:
Pin 1 RS-422 Data TX+Pin 2 RS-422 Data TX-
Pin 3 Audio Send+
Pin 4 Audio Receive+
Pin 5 Audio Receive-
Pin 6 Audio Send-
Pin 7 RS-422 Data RX+
Pin 8 RS-422 Data RX-