A track circuit is an electrical system used in railways to detect the presence of trains on a section of track. It works by sending a low-voltage current through the rails, which creates a closed circuit when a train is present. This helps signal systems determine whether a track segment is occupied or clear, ensuring safe train operations. Track circuits are essential for signal control and train safety. They can be used in various configurations, including DC and AC systems, depending on the railway's requirements. By providing real-time information about train locations, track circuits help prevent collisions and manage train movements efficiently.