The main junction box (J-Box) for the Cabled Array is a Medium Power J-Box (MP J-Box) that receives input voltage at 375 Volts DC and an input data link at 1 GigE. The MP J-Box has one expansion port that passes on the 375 Vdc and 1 GigE data link. This port can be connected to another Medium Power J-Box, or to other specialized equipment that requires higher power or bandwidth, e.g., inductive power coupler systems in docking stations for charging batteries in mobile platforms, or high-definition cameras. In addition, the MP J-Box has eight instrument ports that provide 12 to 48 V and has 10/100BASE-T, RS232 or RS485 data links. There are 18 junction boxes on the system, operational since 2014. The juction boxes are built by the UW Applied Physics Laboratory and are easily reconfigured for specific platform and instrument requirements. The daisy-chain capabilities provide significant growth opportunities for the science community to add additional instruments and platforms.