Which block signaling system uses manual controls or information received by telephone or radio to govern block usage?

• A. Automatic Block Signal System
• B. Block Signal System
• C. Manual Block Signal System
• D. ASC

Answer: (C)

The main idea here is a signaling setup that relies on human authority to authorize train movements. In a Manual Block Signal System, a dispatcher or block operator provides permission to enter a block using direct human communication—by telephone or radio—and signals are cleared or set manually based on that authorization. Trains proceed into a block only after that hand-off of authority, making the human element essential to determine block usage.

This differs from automatic systems, where track detectors and automatic signal logic determine block occupancy and signal indications without needing explicit verbal clearance for each entry. The term Block Signal System can refer to different implementations, but the required method described—manual controls or information exchanged by telephone or radio—points to the manual variant. ASC denotes an automatic control concept, not manual operation.