The 805403-1R is a rectangular box that has many different features. There is an output to PMI connection that is a short 18-pin RS-232 female port. There is an input connection that is a long 15-pin RS-232 female port. Both of the connections to this port screw in. There are factory drilled holes on the bottom of this module that help to keep the internal hardware from overheating. There are 6 screws on the front faceplate of the module that are holding it on. There are two open spots on the faceplate that allow the user access to different circuitry. The bottom spot is labeled ARM CT Signal. The top open spot allows the user to access small resistors and wire connections. Around the open area are the numbers 690, 575, 460, 380, 230, 47, 45, 281, 282, and 283. These numbers indicate the rows and columns of wire connections. When this module is mounted into place, an 805427-1S can be plugged into the small wire connections on the top of the module and then mounted on top of the 805403-1R.