What feature of an access control system requires a user to exit an area before they can reenter?

The feature of an access control system that requires a user to exit an area before they can reenter is antipassback. This security mechanism is designed to prevent unauthorized access and potential tailgating by ensuring that once a user has exited a controlled area, they must go through the proper authorization process to gain reentry. This means that the system keeps track of users' entry and exit times, allowing it to enforce rules that maintain the integrity of access control.

Antipassback is crucial in environments where security is paramount, as it helps ensure that the individuals within a secure area have not simply shared their access credentials with others, thus providing an additional layer of protection against potential security breaches. This is particularly relevant in settings like data centers or secure facilities where monitoring who is inside at any given time is essential for security protocols.