This catagory contains items to help you control your layout without being physically connected to the command center. Most systems use radio signals to accomplish this, however, all Digitrax Handheld throttles come factory equipped with the ability to send infrared(IR) commands with the addition of a UR90 infrared receiver. The latter is a "line-of-sight" system (like most TV remotes), usually requiring the use of more than one UR90 on a layout, unless it is very small.