Abstract: An emergency call system includes a private branch exchange which includes a channel section, a storage, and a controller, wherein when any of the plurality of extension terminals originates an emergency call using a representative telephone number of the private branch exchange to a command system, the channel section establishes a channel which enables communication between an emergency call extension terminal and the command system, and wherein when the emergency call extension terminal disconnects the emergency call during the emergency call in-progress state, the channel section disconnects a channel to the emergency call extension terminal and keeps connecting a channel to the public network, thereby establishing an emergency call line-hold state.

Abstract: To provide a network control system which prevents a system performance degradation caused by generating/updating routing information and enables a connection request to be established reliably. The significant change detection module 33 sets the flag 33a to on when a pre-determined change occurs. The first timer 21 determines the longest interval at which the routing information 24 is updated, while the second timer 22 determines the shortest interval at which the routing information 24 is updated. When the first timer 21 times out, the routing information update control module 23 unconditionally updates the routing information 24. When the second timer 22 times out, the routing information update control module 23 updates the routing information 24 only if the flag 33a is on.