Which device stops the platform when an obstruction exerts a force of 20 N or more?

• A. Capacity Plate
• B. Obstruction Devices
• C. Safety Mechanism
• D. Closing Speed

Answer: (B)

Obstruction devices are the safety components that detect resistance when something blocks the escalator and stop the platform when the force reaches a preset level, such as 20 newtons. This threshold is chosen so the system responds quickly to real obstructions while ignoring minor contacts. The capacity plate only specifies the maximum passenger load and doesn’t trigger a stop. The term safety mechanism can refer to overall protection, but the specific function of stopping due to an obstruction is handled by obstruction devices. Closing speed affects how fast the steps move or how quickly the system can come to rest, not whether an obstruction is detected.