Surveillance installation operation using sensor network buses

摘要

The detectors (D) are arranged around a loop (10) and one or more branches (11). For a period of one or two minutes, preferably 80 seconds, the network is interrogated along a single two-wire bus. For a period of about an hour, the station periodically checks the correct function of the detectors. The time for these requests and their responses is very short allowing the central station to manage the network in the free time. The station reads from an internal memory sequential data which each detector produces to assure their operation. The station can test detectors and change operating thresholds or take faulty detectors out of service. The station can also display evacuation and other messages over the bus.