When used with the SB5, the PCP (Power Cab Panel ) functions only as an extension of the cab bus jacks on the sb5. The type of cab bus cables (4 or 6 wire) makes no difference. In this case which SB5 cab bus jacks you use make no difference either, the cab bus jacks on the SB5 are both the same, and all 4 jacks on the PCP work all the same now. They are all just to extend the cab bus jacks on the front of the SB5.
The PCP can be used as a regular Universal Throttle Panel (UTP) with the SB5 under two important conditions:
1. Do not plug in the power supply that came with the Power Cab.
2. Do not connect the track output to the Power Cab panel.
In this configuration the panel is passive and gets powered by the cab bus output of the SB5.