Which of the following is NOT a feature of multi-beam door protection devices?

Multi-beam door protection devices are designed to improve safety around elevator doors by using multiple beams to detect obstacles and prevent injury or damage. Continuous scanning is a vital feature as it allows the device to constantly monitor the area in front of the doors for any obstructions. This ensures that the elevator doors do not close on a person or object, thereby enhancing safety.

Obstacle detection is another key feature, as it allows the device to identify any objects or individuals in the door's pathway. This capability is crucial for preventing accidents and ensuring the doors remain open when something is detected, which directly promotes user safety and enhances the functionality of the elevator system.

Safety enhancement, as a feature, refers to the overall improvement in the safety of the elevator system, bolstered by the combined functions of continuous scanning and obstacle detection. Multi-beam systems contribute significantly to elevating safety standards for elevator operations.

In contrast, manual operation is not a feature associated with multi-beam door protection devices. These devices are designed to automate the safety process, reducing human intervention and potential error in door operation. Hence, it stands out as not fitting the typical features of such systems.