I really liked the Control Tower (40205). Just like at Indianapolis, it has a large digital readout that vertically shows the race position of up to eight cars. At the top of the display, either the number of laps remaining or the time remaining is shown. A quick glance shows all the race positions. If #3 is on top, then car #3 is in first place. If #5 is in the second position down, then car #5 is in second place, and so on. As each car crosses the starting line, it’s race position is immediately updated and displayed, and it’s always accurate. The Control Tower is mounted on a special 20mm track section and gets its power through the track, so it doesn’t have to be plugged into the Control Console. It rotates a full 360 degrees so you can place it anywhere on your layout for best visibility. Not only that, but you can put as many Towers on the layout as you wish, and they will all instantly and continually update as each car individually crosses the start line.
That brings me to the Sensor Track (40206) sections that plug into the accessory socket of the Console when using the multi-lane sections. These special Sensor Tracks transfer power to the additional two lanes. They’re directional, so it’s important to remember that all racing is clockwise with N-Digital. You position these two-lane sections directly opposite the Console/power section so laps can be counted as the car passes the start line. Like the power section (Control Console) these Sensor Tracks have starting grid markers painted on the surface. Do not confuse them with the Grid Tracks or you won’t be able to count laps on lanes 3-8! 
There’s a Grid Track (10114) that has grid marks painted on them that you use to evenly space cars at the start of a race. These are different and are not Sensor Tracks. They don’t have a cable that plugs into the Control Console. These Grid Track pieces can be used on standard analog layouts as well.
