[Al Skierkiewicz]

The banner sensors are not phased nor do they use any other type of signal identification. They emit visible red light with a sensor that is optimized for use with retroflective objects. (i.e. reflective objects that reflect some light in all directions.) They have a distinct area of view that for our sensors is at maximum 8 inches in diameter. Signals that appear outside that area of sensitivity are not picked up by the sensor. As to "seeing the diamond plate under the player's station this is possible if the sensor to plate angle is close enough to perpendicular that a significant amount of light is reflected back to the sensor. Another sensor emitting light in the direction of the receiver (and within the diameter of sensitivity) could produce a false trigger. Bright lights may also confuse the sensor but camera flashes are very short duration and would not normally do much in the way of interference.
In FLL there were a number of devices that would at the very least confuse the Mindstorm product. Many security cameras and palmcorders have Infrared illuminators and range finders that would swamp the IR communication port or set the controller to think it was being communicated with. In addition, the latest Mindstorms are also addressable with a handheld infrared remote control to override internal programming. In an effort to minimize such interference, teams were advised to cover the IR ports with electrical tape to prevent any interference during competition.