Access control refers to the process of granting or denying entry to a specific area or building based on a set of criteria. This can include measures such as key cards, biometric authentication, or keypads. Access control systems are used to restrict access to sensitive areas or to control the flow of people in and out of a building. The goal of access control is to ensure the security of a building and its assets, while allowing authorized personnel to enter and move around freely. Access control systems may be integrated with other security systems, such as video surveillance and alarms, to provide a comprehensive security solution. Additionally, access control systems may be programmed to grant or deny access based on factors such as time of day, location, or security clearance level.