What components make up an interlocking system?

An interlocking system is comprised of signals, switches (also known as points), track circuits, and a control logic system that ensures the safe and coordinated movement of trains by preventing conflicting routes. Signals are the visual displays that indicate to train crews whether they are permitted to proceed, and at what speed. Switches are the movable sections of track that allow trains to be routed from one track to another. Track circuits detect the presence or absence of trains on a section of track, providing critical information for preventing collisions. The control logic system, which can be mechanical, electrical, or electronic, is the heart of the interlocking system. It receives inputs from the track circuits and switch positions, and it controls the signals and switches to ensure that only safe routes are set. The control logic system is designed to prevent conflicting routes from being set simultaneously, ensuring that trains cannot be directed onto the same section of track at the same time. It also prevents switches from being moved while a train is approaching or occupying the switch, preventing derailments. For example, at a railway junction, the interlocking system would ensure that only one signal is cleared for a train to proceed through the junction, and that the switches are set to direct the train onto the correct route. The system prevents other signals from being cleared that could allow another train to enter the same section of track, preventing a collision. The interlocking ensures that the status of switches and signals are properly interlocked, meaning they can only be in a safe and compatible state relative to each other, guaranteeing safe train movement.