Thermal Counter– a specific type of counter using proprietary technology, manufactured by Irisys. This type of counter is mounted on the ceiling above an entrance and counts people by monitoring the difference between the background temperature and the temperature of count targets passing underneath. As such, unlike many standard video counters, the thermal counter is not affected by ambient light. These counters are commonly used within retail stores, shopping centres, art galleries, visitor centres and libraries. Irisys also produce a version of the counter which is capable of monitoring tailgating through turnstiles to assist with building security management.