| 摘要 |
A property protection system has a central base station unit 2 with a number of satellite item protection units 1, each associated with an item of property to be protected. The base station unit periodically emits coded polling signals to the item protection units and receives responses from them. If an item protection unit fails to respond to the polling signal, an alarm condition is signalled. The item protection units can also include sensors and can be intelligent so that they can respond directly in initiating an alarm when a specific event is sensed. Each base station unit will be responsible for a specific geographical area, but if an item of property, with its item protection unit is moved from its expected location, its new position can be found/tracked by triangulation from several base station units. <IMAGE> |
