7830 Intruder Alarms (1) 7833 Emergency, warning, information and general alarms (4) Emergency, warning, information and general alarms 7834 Gas and liquid detection systems (0) Systems using automatic sensors to detect the presence of a specific gas when the atmospheric concentration rises above a selected level or to detect the levels of liquids in containers outside of preset levels 7835 Access control (15) Systems for monitoring and controlling persons moving into and out of buildings and in spaces within buildings and areas adjacent to the building and for recording, processing and displaying the information related to the movement of persons 7836 Intruder detection systems (3) Security systems including systems to detect the movement of persons and things, using surveillance equipment and sensing devices, with facilities for recording, processing and displaying the data obtained and for operating lighting, barriers, etc.