Which of the following devices is commonly used to grant physical access within an ACS?

The device known for granting physical access within an Access Control System (ACS) is the card reader. Card readers are designed to authenticate users by reading access credentials stored on cards, such as keycards or RFID cards. When a user presents their card to the reader, the device communicates with the ACS to verify the identity of the individual, determining whether to grant or deny entry based on the permissions assigned to that particular credential.

Motion detectors, while important for security, primarily serve to detect movement and trigger alarms rather than to grant access. Smoke detectors function to identify the presence of smoke or fire and ensure safety; they are not designed for controlling access. Surveillance cameras play a key role in monitoring the premises and recording activities, but they do not physically control or grant access to individuals. Each of these other devices has its specific function within a security ecosystem, but the card reader is the tool specifically aimed at managing physical access.