Hey GRJ,
There are labels on the ends, one is TIU, the other reads TMCC. Following the labels, and putting the ends in the sockets on the TIU and TMCC I get no indication of communication between units. The TMCC engine on the test track is silent because it hears the signal from the TMCC Control box. The engine wakes up with the CAB-1.
I am going down to the club (NCOG) layout in the morning, to try to sort out the problems we are having with DCS signal loss and level. I can swap the cable and test it on the layout.