In the past, people were generally counted using hand-held counting devices known as ‘clickers’. The holder increments the clicker by pressing a button each time a person passes through an access point. This system was not particularly accurate and there was no easy means of keeping track of the total count of multiple clickers when used to count people into the same area. Modern systems use an electronic means of recording people as they pass through an access point.

To be able to accurately count visitors entering a venue, each entrance must have a control area where they can be monitored as they enter.  Ideally, they need to enter one at a time. Typically, a control area will be fitted with one or more turnstiles. Each turnstile allows just one visitor to pass at a time and can usually provide an output signal each time a visitor enters.

Where it is not practicable to fit mechanical turnstiles, there are other options available. These are usually referred to as ‘optical’ or ‘electronic’ turnstiles. Here, a device is used to optically monitor the movement of people in and out of an access point and raise an alarm when a person enters without authentication (e.g. presenting a valid pass-card to a reader). These devices can also provide an output signal each time an authorised person enters.

The counting system takes the signals from the turnstiles to maintain a count of people entering a controlled area and computes the data as necessary to provide the required information and/or alarm signals. Typically, the counting system will provide comprehensive on-screen information to the management and/or display count values at key locations around the venue. It may also hold critical value thresholds so that it can provide a warning whenever a count reaches a critical value.