What describes an Automatic Block Signal?

What describes an Automatic Block Signal?

• A. A fixed signal displayed at the entrance of a block.
• B. A blue signal used to protect workers.
• C. A block signal that is activated either by track circuit or in conjunction with interlocking or controlled point circuits. This block signal automatically indicates track condition and block occupancy.
• D. A signal located in the engine control compartment that indicates track occupancy.

Answer: (C)

Automatic Block Signals are part of the ABS system where a block signal is set automatically based on track circuits and interlocking logic. The signal is controlled by a track circuit detecting whether the block is occupied, or by interlocking/points circuits that coordinate multiple signals and switches. As a result, the block signal automatically shows the track condition and occupancy without manual intervention, guiding trains safely from one block to the next. Other options don’t fit because a fixed signal at the block entrance isn’t necessarily automatic signaling, blue signals are used for employee protection rather than block occupancy and through-traffic control, and a signal in the engine compartment is a cab/engine indicator, not an Automatic Block Signal.

Automatic Block Signals are part of the ABS system where a block signal is set automatically based on track circuits and interlocking logic. The signal is controlled by a track circuit detecting whether the block is occupied, or by interlocking/points circuits that coordinate multiple signals and switches. As a result, the block signal automatically shows the track condition and occupancy without manual intervention, guiding trains safely from one block to the next.

Other options don’t fit because a fixed signal at the block entrance isn’t necessarily automatic signaling, blue signals are used for employee protection rather than block occupancy and through-traffic control, and a signal in the engine compartment is a cab/engine indicator, not an Automatic Block Signal.