What is the secure entry system with two gateways, only one of which is open at any one time?

What is the secure entry system with two gateways, only one of which is open at any one time?

• A. Turnstile
• B. Double-door entry
• C. Interlock door system
• D. Access control vestibule

Answer: (D)

The key idea is a controlled entry buffer that sits between the outside and the secure area, using two doors that are interlocked so only one can be open at a time. This setup creates a secure vestibule where your credentials are checked at the first door, and only after that door is opened and you pass through does the second door unlock. The interlock ensures tailgating can’t happen and provides a clear checkpoint before access is granted, making it the most appropriate description for a system with two gateways that can’t be open simultaneously. Other mechanisms like a turnstile or a simple two-door entrance may restrict flow or rely on one door but don’t guarantee the enforced single-door-at-a-time posture or the integrated access-control buffer that a vestibule provides.

The key idea is a controlled entry buffer that sits between the outside and the secure area, using two doors that are interlocked so only one can be open at a time. This setup creates a secure vestibule where your credentials are checked at the first door, and only after that door is opened and you pass through does the second door unlock. The interlock ensures tailgating can’t happen and provides a clear checkpoint before access is granted, making it the most appropriate description for a system with two gateways that can’t be open simultaneously. Other mechanisms like a turnstile or a simple two-door entrance may restrict flow or rely on one door but don’t guarantee the enforced single-door-at-a-time posture or the integrated access-control buffer that a vestibule provides.