Which of the following enhances security by limiting access to authorized personnel only?

Access control systems are crucial for enhancing security by strictly regulating who can enter or access specific areas within a facility. These systems can employ a variety of mechanisms, such as key cards, biometric scanners, and PIN codes, to ensure that only individuals who have been granted permission can gain entry. By establishing these credentials, access control systems effectively limit access to authorized personnel, thereby reducing the risk of unauthorized entry and bolstering overall security.

The other options do not serve the same purpose of restricting access. Surveillance monitoring primarily focuses on observing and recording activity to deter or document breaches, but it does not physically prevent unauthorized access. Open door policies promote transparency and accessibility, which can inadvertently allow unauthorized individuals to enter. Public access areas are designed specifically to invite public entry, contradicting the goal of limiting access to only authorized personnel.