The scale connectors are 4 pin mini-DIN type that mount to the back panel with 4-40 x 1/2" black machine screws. You can install up to five scale connectors with the DRO-550. The connectors listed in the bill of materials have a hole on either side that must be tapped 4-40 before mounting with the screws. This is most easily done with a small hand tap.
After tapping, mount the scale connectors to the back panel with the 4-40 x 1/2" screws.
The edge finder and tachometer connectors are 3.5mm stereo jacks. The DRO-550 supports up to two of each. Remove the nuts included with the connectors and mount them on the rear panel. If MTA plugs are used on the other end of the cables, then they must not be installed until after the stereo jacks are installed because the MTA plugs will not fit through the hole for the stereo jack. Solder the wires to the stereo jack as shown in the cable construction page.
The DC power connector is a standard 2.1mm type. The connector listed in the bill of materials is a snap-in type that is simply pushed into the hole drilled into the back panel. Depending on the tolerances of the hole, you may need to put a few drops of hot glue or epoxy to assure that the connector does not pull out of the hole when the power cord is removed.