DPC-1 (5417-557) and DPC-USB (5417-1251) are special configuration cables for a peer to peer RS232 (DPC-1) and USB connection between a PC and Woodward devices (such as easYgen-1500, easYgen-2000, DTSC-200, LS5 controllers, etc).
The RJ-45 plug is a special RS232 interface (non-standard voltage levels) and uses a CAT-5 or -6 cable, but does not carry Ethernet.
The small black box is a galvanic isolation and a voltage divider from 5 VDC to 3.5 VDC
USB driver available here:
https://wss.woodward.com/manuals/PGC/SW_Tools/USB_Drivers
DPC is required for following products:
MFR-11,-12,-13,-15,-2,-31,-32,-300
AMG2, AMG3, GCP-20,-21-22, GCP-30,-31,-32
LS-4,-5
easYgen-300, -1500
easYgen-2000
DTSC-200
IKD1M