interlocking

Linked, locked, or fitted closely together.

All societies have three key interlocking elements: Religion, economics, and politics.

An arrangement of signal apparatus that prevents conflicting movements through a set of intersecting tracks, such as junctions or crossings.

There was still no attempt to arrange interlocking between points and signals; that came later. In 1856, John Saxby carried out the principle involved in interlocking—the prevention of signals and points being in conflicting positions—and erected apparatus to do that at this same junction.

In addition to the usual interlocking between conflicting signal and point levers achieved by electric locks, track circuits, when occupied, hold signals governing entry to the relevant line at danger; [...] The up main through inner home signal was held at danger by interlocking, because the track circuits of a conflicting route ahead of it were occupied by another train [...].