The ability to maintain the Overlap free of locking where there are Facing
PointsItems of permanent way which may be aligned to one of two positions, Normal or Reverse, according to the direction of train movement required. More and a choice of overlap exists, thus enabling late selection of the
overlap while the train is approaching. Usually associated with Time Of
Operation Locking and Conditional LockingInterlocking between two signalling functions that are dependent upon the state of other Signalling Functions. More requirements.