IL: Control Table
In the first draft of interlocking schema the stub element "ControlTable" was foreseen. It shall be clarified, whether this feature is really needed and what content is required.
Typically, the signaller calls the route after which the interlocking sets the elements in the state as required per control table. Control tables, colloquially referred to as route tables or interlocking tables, are sets of elements associated with a required state. If all elements are asserted in that state, the route is locked and made available to a particular train. In other words, if all track elements are in the correct state, the interlocking sets the entry signal to proceed. A route is composed of a number of track elements, and their respective status. Track elements are grouped in (1) approach locking, (2) en route elements and (3) off route elements.
- When an approach section is occupied, the interlocking locks the route.
- The en route elements are track elements that the train encounters. The status of these elements is given. The route is locked only when the elements report this status. The elements are ordered as the train encounters them. This allows graph traversal algorithms to compile the list.
- Off route elements typically provide flank protection and overlap. The elements must be in the given position for the route to be locked. These elements are by nature not situated within the route, hence the name off route.