There are two important numbers for radar scanners. The RSB number that tell what physical gear box was used in the production of the unit and the RTR number that tells what electronics were placed in that RSB gear box. Normally to determine model and compatibility, we need both of these numbers from the radar scanner. There were at least two RTRs used in the RSB0087 gear box. The -068 (1712 radar) and the -070 (1722 radar) are the only two I am aware of. Normally for the NavNet series one RDP131 display; the correct scanner would be the -070 making it a 1722C (Navionics) or 17232/NT (C-Map) model radar/plotter unit. The proper scanner cable should have a large 24 pin rectangle connector to connect to the display. The -068 scanner from the older 1712 radar would normally have a small black round 10 pin connection; that wouldn’t fit the RDP131. If you have a 1712 scanner and the 1722C display, they are not considered compatible.