IBM RT with 5085 graphics processor

I picked up a very nice RT system the other day from a list member which includes the 5085 graphics processor and 5081 colour display. We've just been setting it up today (or trying to), and an obvious question arises... The 5085 has some sort of comms input ability on a BNC connector (and output on another BNC, but that's terminated). The RT has a little "breakout box" which hooks up to the 5085 link card on one side and has four BNC outputs on the other. My *assumption* is that one of these outputs (and the breakout box came with a coax cable already hooked up to BNC #1) links to the BNC input on the back of the 5085, forming the comms channel between the 8085 and the RT. However, it would be nice if someone can verify this! The RT documentation doesn't cover the 5085 link option (so far as I've found yet, anyway). The 5085 documentation doesn't cover it either (as it only details how to hook the 5085 up to the peripherals and then boot the hardware). Obviously I'm a little reluctant to go randomly plugging cables in, particularly as the breakout box has four BNCs on board - although it could well be that the RT 5085 link board was capable of driving up to four 5085 processors independently. Google seems to know almost nothing about the 5085 option :-( cheers Jules