If you are reading this then chances are you have access to both the SAR CAD and the DMV section of the CAD. As previously stated, the unique key for the DMV section of the CAD is given to hand-picked sever members and given to all members of the Law Enforcement faction.
Once you have entered the correct key, you will now be able to see a tab labeled 'DMV' on your CAD home screen. Clicking on this tab will take you to a secondary page, which will include another tab labeled 'Street Signs'. Entering this page will guide you to main area where all CMS displays, across San Andreas, can be monitored & controlled.
Given to you is the exact road name and postal of each individual CMS board, including the direction of the flow on traffic on that specific road. You are also given a Search Bar, which you can use to search for a specific road name or postal to save time. Each CMS display is divided into rows A, B & C and this is also represented in each display controller on this page. Although the controllers do not show that the text is centered, rest assured it will be centered in game. Each row on the controllers has a 14 character limit.
Below you can see an example of a properly formatted CMS display on one of the controllers.