The physical barriers used in access control include doors fitted with an electric locking device, turnstiles, speed gates, lifts, parking gates, bollards and vehicle barriers. They all require a signal from the access controller before they will permit access.
Bollards, gates and vehicle barriers are usually accompanied by vehicle detectors that prevent more than one vehicle passing through each time they open on in response to the signal from the controller. Turnstiles and speed gates are designed to allow just one person to pass through each time they are activated. Lifts will only stop at restricted levels and open their doors if they are permitted to do so by the access controller. However, they can’t control how many people get out on that level.
Because a simple door has no means of ensuring that only one person passes through when it is unlocked, strict rules must be in place forbidding authorised personnel from allowing unauthorised people to pass through the door. Where this is not practical, then a one-pass system such as a full-height turnstile should be fitted. Alternatively, an electronic or ‘virtual’ turnstile can be fitted to detect how many people pass through the door when it is unlocked. It can’t prevent them from passing through but it can raise an alarm to attract the attention of security guards or activate a camera.