Patent ID: 7580361

Claim:
A network system comprising: a plurality of monitoring apparatus for determining a state of a monitored apparatus based on monitored apparatus information received from the monitored apparatus via a network, the plurality of monitoring apparatus including a first monitoring apparatus and a second monitoring apparatus, the first monitoring apparatus receiving the monitored apparatus information at a first time, the second monitoring apparatus receiving the monitored apparatus information at a second time, and the second time being different from the first time, wherein: the first monitoring apparatus is designed to transmit state information, indicating the state of the monitored apparatus, to the second monitoring apparatus, when the first monitoring apparatus detects a change in the state of the monitored apparatus, the second monitoring apparatus is designed to determine the state of the monitored apparatus based on the monitored apparatus information and the state information, the first monitoring apparatus is designed to transmit specific state information, indicating that the monitored apparatus is disconnected from the network, when the first monitoring apparatus does not receive the monitored apparatus information to be received at the first time from the monitored apparatus, and the second monitoring apparatus is designed to determine that the monitored apparatus is disconnected from the network when the second monitoring apparatus receives the specific state information and when the second monitoring apparatus does not receive the monitored apparatus information to be received at the second time from the monitored apparatus.