Alarm for personal computer connected to twisted pair network

摘要

The alarm includes an alarm centre (1) operationally connected to a hub (3), that computers (13a and 13b) in the network are connected via a first alarm (4) incorporating an input for connection to the hub. An output (23) is operationally connected with a network board in the computers and a connection for interconnection with a second alarm (5) or connection unit (10). A closed line is formed to the alarm unit. The hub, via two conductors, not used for communication between the computers, transmits a request generated in the alarm centre to each of the alarm units to detect the associated computers and to notify the alarm centre when a change occurs in the associated computer.