The anti-pass back system prevents a card holder from passing their token back to a second person, to gain entry into the same controlled area. When a token is presented twice in quick succession, it will fail to grant access to the controlled area.
The anti-pass back feature also improves the accuracy of roll call and 'Last known position' reports, and deters tailgating. If a user should follow a colleague out of an area without presenting their own token, their error is discovered when they try to return to the controlled area. Access into the area will be barred, as their last known location is shown as still being inside.
Logical anti-passback is used on sites where strict access control is important. It requires both IN and OUT readers at each area boundary. The system must see a user card leave an area before allowing access in the opposite direction. This is particularly suited to deter users from tailgating each other. If they do not read out of an area, they will not be allowed back in, no matter which door they try. Similarly, if a user tailgates another onto a site, the system can prevent that user from accessing other areas of the site, until they have fobbed into the site correctly
This system is suited for a general office environment. As long as a user obeys the logical anti-passback rules, they may re-gain access to an area immediately. If, however, the user tailgates another user out of the area they will be allowed to re-enter after the specified time period from their previous valid access. This waiting period should inconvenience the user but will avoid them being trapped in an area
Timed anti-passback prevents a user card from entering the same area twice during a set time duration. This is useful where there is an exit button or free access turnstile and no OUT reader.