A block signal system wherein the use of each block is governed by block signals controlled manually, by block-limit signals or both, upon information received by telephone, radio or other means of communication.

• A. Block Signal System
• B. Manual Block Signal System
• C. Automatic Block Signal System
• D. Speed Controlled Train

Answer: (B)

The main idea is that block usage is controlled by human operators through signals, with instruction and status shared by telephone, radio, or other communication. This describes a Manual Block Signal System, where the dispatcher or signalman determines when a block is clear and issues authority to proceed using block signals or block-limit signals that are operated by hand or by manual means. The key is that control rests with people, not automatic track circuits driving the signals. The description explicitly calls for signals governed manually and communications-based guidance, which distinguishes it from automatic block systems (where track circuits detect occupancy and drive signals automatically) and from other, less relevant concepts.