What mechanism is used to safely ensure doors do not close on obstructing objects?

The mechanism that safely ensures doors do not close on obstructing objects is an obstruction detector. These detectors are specifically designed to sense when an object is in the path of the closing door, preventing it from closing completely. When an obstruction is detected, the system can either stop the door from closing or reverse its direction to avoid potential injury or damage. This is a critical safety feature in elevator systems, enhancing passenger safety by ensuring that doors do not crush objects or people.

While other methods like edge sensors and force reversal also serve safety functions, an obstruction detector is dedicated to sensing and responding to obstacles directly in the doorway. Edge sensors typically work by detecting pressure along the door's edges, whereas force reversal relies on detecting resistance encountered by the door. Nudging, on the other hand, refers to the action of pushing the door slightly open if it encounters some force. These mechanisms complement each other but do not specifically address the direct detection of obstructions like the obstruction detectors do.