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 circuit. When a train occupies the track, it completes the circuit, allowing the system to signal that the track is occupied. These circuits are essential for ensuring safety in railway operations. They help control signals and prevent collisions by indicating when a section of track is clear or occupied. Track circuits are a key component of railway signaling systems, contributing to the overall efficiency of train movements.