Most of the TMCC stuff was modular including all the accessories, lights, couplers, etc. The plugged in using relatively simple plugs. Just before TAS decided not to do it any more there were modular wiring harnesses that would have cut assembly time considerably
Here are some pics of the E-couplers I install on my set of Weaver E-8. It took an exacto knife to release the small pins from the white plastic modular end.
Assuming the wires are long enough these two assembles should plug into the board. FCP front coupler, RCP, rear coupler. ERR used the same plugs at least on the original Beep upgrade boards that had the couplers involved.
But the board easily could be installed either direction. So you had to be careful about plug-ins.
This early Beep board had coupler plug-ins. note to the far left on either side of the board. ERR install in a Rich Yoder GE 44 tonner. Yes, I got it wrong the first time. Silly little thing does have an "F" on one end, Forward. I had to reverse the plug-ins.
Couplers are fabricated from Atlas articulated couplers used on their SW series.
Atlas has a nice detail piece that covers the electro couplers.