Which device must emit 80-90 dBA sound at 3,000 mm?

• A. Bell
• B. Intercom
• C. Audible Signaling Device
• D. Public Address

Answer: (C)

Audible signaling devices are designed to give a clear warning to riders about escalator or moving walk operations, so they must produce a defined loudness at a specific distance. The requirement of 80-90 dBA at 3 meters ensures the warning can be heard over typical station noise levels and at a practical distance from the equipment. Other devices serve different roles—bells can be part of signaling but aren’t mandated to a fixed decibel level at a set distance, intercoms are for two-way communication, and public address systems are for announcements rather than a standardized warning signal. This is why the audible signaling device must meet that 80-90 dBA at 3,000 mm specification.