Trailer wiring harness diag?

[chad1966]

I picked up a OE volvo trailer hitch and the wiring harness that came with it has me a bit confused. Ok so I understand that 240's have separate turn and tail light signals. The harness has this additional box that was hooked inline that I am assume was for the tail lights for the trailer but I am having a hard time wrapping my mind around how it works. The 2 solid green wires that are attached on the small box labeled H617 were attached seperatly inline with the green and yellow wires going to the trailer.The black and yellow were cut and I dont know where they were attached. What does the small box labeled H617 do? How do I get running lights with this setup. Thanks.