What are magnetic key cards used for in security systems?

Magnetic key cards are primarily used for access control in security systems. When a magnetic key card is swiped against a card reader, it allows authorized individuals to gain entry to restricted areas or buildings. This system works by encoding specific information on the card, which is then read by the card reader, validating the person's access rights.

This method provides a reliable and secure way of managing who can enter certain spaces, as it can be easily updated or deactivated when needed, such as when an employee leaves the organization or loses their card. This functionality enhances security by restricting access to only those who are authorized, making it an essential component of modern security systems.

The other options do not reflect the primary function of magnetic key cards, as they are not used for video surveillance monitoring, triggering fire alarms, or direct communication with security personnel.