What defines the limits of track use governed by specific signals?

The limits of track use governed by specific signals are defined by a block. A block is a section of track that is not occupied by a train and is governed by signals that inform the engineer about the state of the track ahead. The use of blocks allows for safe train operations, as it helps in preventing collisions by ensuring that only one train occupies a block at any given time.

Blocks are essential for signaling systems, as they determine where trains can safely travel. Signals indicate whether a block is clear or occupied, and this information is crucial for the operation of trains. By managing the movement within these defined sections, train operations remain organized and safe, ensuring that engineers can proceed at appropriate speeds or come to a stop when necessary.

The other choices do not provide a framework for defining track use in terms of signals. Equipment refers to the tools and machinery used in train operations, a deadhead train signifies a train running empty or without passengers, and a freight train refers to a specific type of train that carries goods. None of these terms define the functional concept of track limits in the context of signaling and safety.