In an access control system, what is the main function of a card reader?

The primary function of a card reader in an access control system is to verify user credentials before granting access. When a user presents their access card, the card reader scans, reads, and interprets the data encoded on the card. This data typically includes a unique identifier linked to a user profile stored in a database.

Upon validating this information, the system determines whether the individual is authorized to enter a specific area. If the credentials match, the access control system sends a signal to unlock the door or grant access to the designated area. This process is crucial for maintaining security in controlled environments, as it ensures that only authorized personnel are allowed access to sensitive or restricted areas.

The other functions suggested in the options do not align with the primary role of a card reader in an access control system. While connecting an alarm system to a power supply, locking and unlocking doors, or generating access reports may be important aspects of an overall security strategy, they are not the fundamental purpose of a card reader itself.