What is a defined entry point that requires passing through two doors, with only one door being open at a time?

The mentioned entry point where individuals must pass through two doors, with only one door being open at any given time, is known as a mantrap. A mantrap is specifically designed to enhance security by controlling access to a secure area. It typically consists of two interlocking doors that prevent unauthorized entry or exit.

When someone approaches the first door, they must be validated, often through authentication measures like ID cards, biometrics, or authorization codes. Once they pass through the first door, it will close and lock before the second door opens. This physical design helps ensure that only authorized individuals can enter while minimizing the risk of tailgating, where an unauthorized person might try to follow someone with legitimate access.

This security mechanism is particularly effective in environments that require high security, as it not only restricts access but also allows for monitoring and controlling who goes in and out of sensitive areas. The other options, while related to security, do not encapsulate the specific two-door design with interlocking functionality that characterizes a mantrap.