What is it?
Anti passback is a security system feature that is used to prevent users from passing their credentials (such as access card or similar device) back to a second person to enter a security controlled area, such as a car park or employee building. It can also stop users to enter the controlled area by following or tailgating another person.
Anti passback’ s purpose is to prevent misuse of such access control systems, but can also be used to count the users (cars or people present in the building) or can be combined with many other features to fulfill high security requirements in areas where there is an “in” reader at the entry gate and an “out” reader at the exit gate.
How does it work?
The anti-passback feature works on the basis of a specific sequence in which access cards must be used in order for the system to grant access. For every use of a card at the “in” reader, there must be a corresponding use at the “out” reader before the card can be used at the “in” reader again. For example, this works fine at the parking lot, because the driver would normally swipe their card at the “in” reader to get into the lot and swipe it at the “out” reader to get out of it. As long as the sequence is “in – out – in – out – in – out”, the system will work fine. However, if the driver swipes his card at the “in” reader to get in, and then passes his card back to a friend, the card would not work the second time because this would create an “in – in” sequence, which is a violation of the anti-passback rules and access would be denied.