Which device trips at a maximum pressure of 15-30 pounds?

• A. Obstruction Sensing Device
• B. Top Terminal Limit Switch
• C. Platform Hand
• D. Masonry Anchors

Answer: (A)

The main idea is how safety devices on an escalator detect an obstruction and stop the machine. An Obstruction Sensing Device is built to sense contact on the moving steps and trip when a certain force is applied, in this case a maximum of 15–30 pounds. When that pressure is reached, the device signals the control system to shut down the drive, stopping the escalator quickly to prevent injury. This specific pressure range balances responding to actual obstructions (like a hand or clothing) without being set off by minor contact or debris.

The Top Terminal Limit Switch, on the other hand, is a safety device that stops or reverses the escalator when it reaches the end of its travel at the top landing; its function isn’t tied to pressure on the steps. The Platform Hand-related interlock serves a different safety purpose near the platform area and isn’t a pressure-activated stop on the steps. Masonry anchors are just mounting hardware and don’t participate in trip or safety sensing.