RYG-RYG. This signal differs from other available invisible signals in that it properly recognizes distant aspects, when operated in Block mode, which is the default. It can also be used for other purposes. When operated in Fixed mode, it operates as a fixed signal. For example, it can be use as an exit signal from signalled territory to unsignalled territory, either using the default of Always Clear (to follow speeds set by signs) or Restricting (to operate at 20 MPH). It can be used as a fixed distant, by setting it to Always Approach. To stop trains (at the end of track, for example), set it to Always Stop. The Stop-and-Proceed setting can be useful in yards.