Comprehensive and Detailed Explanation From Exact Extract:

Badge readers are electronic access control systems that require authorized users to scan a badge (e.g., RFID or magnetic strip cards) to gain access to restricted physical locations. These systems typically log all access attempts—successful or denied—providing both detection and recording of access events.

A. Bollards are physical barriers to prevent vehicle access.

B. Video surveillance can record access visually but does not track identity unless integrated with access control systems.

D. A fence restricts access but doesn't detect or record who entered.