What type of security system restricts access to unauthorized users at certain times?

The type of security system that restricts access to unauthorized users at certain times is an access control system. Access control systems manage who is allowed to enter or exit certain areas within a facility based on predetermined limits, such as time of day, individual identity, or specific permissions.

These systems provide a way to enforce security protocols by ensuring that only authorized personnel can gain access at specific times. For example, a business may have an access control system that allows employees to enter the building only during working hours, while restricting access to outsiders or even employees outside those hours. This can be achieved through various means, such as key cards, biometric scanners, or PIN codes.

The other options, while related to security, serve different purposes. Surveillance systems primarily focus on monitoring and observing an area for suspicious activity, alarm systems are designed to alert users or authorities to breaches or emergencies, and monitoring systems typically involve tracking and notifying users about specific conditions or events, rather than controlling access.