The GigaPlus/GigaPro is supplied with a three position locking terminal block for connecting the -48 VDC power supply. The middle position is Earth Ground and the outer two positions are -48 VDC.
Although only one of the -48 VDC connections is required, dual power supplies can be used to provide redundancy by connection the left position to one supply and the right position to the other supply. Internal diodes prevent current from flowing the wrong direction in the case that one of the power supplies should fail. Under normal operation the current will be divided between the two supplies.
The middle connection, Earth/Ground, should be connected to the a Positive (+) terminal on the power supply.
The wiring used should be two stranded copper wires of a size no smaller than 18 AWG. The wires should be twisted together to reduce susceptibility to noise. At least one turn per inch is recommended. Tighten the two #2 screws to the chassis after installation of the connector to prevent it from pulling out.
The IDU ships with a ferrite to reduce noise entering the unit through the power cable. To install the ferrite, loop the power cable through at least once and close the ferrite. Be sure to install the ferrite as close as possible to the IDU power plug to improve the noise rejection.