Wikipedia
A mantrap, air lock, sally port or access control vestibule is a physical security access control system comprising a small space with two sets of interlocking doors, such that the first set of doors must close before the second set opens Airlocks have a very similar design, allowing free ingress and egress while also restricting airflow In a manual mantrap, a guard locks and unlocks each door in sequence An intercom and/or video camera are often used to allow the guard to control the trap from a remote location In an automatic mantrap, identification may be required for each door, sometimes even different measures for each door
Mantrap_(access_control) - Wikipedia, the free encyclopedia