Congestion Control Function

If an exchange is overloaded with heavy traffic well in excess of its capacity, owing to a social incident, a disaster, or a surge in telephone requests, it may adversely affect peripheral associated exchanges as well as that exchange, jamming the entire network.
The congestion control function prevents an unexpected amount of traffic from affecting the entire network, for example, by restricting calls from being originated.

Outgoing call restriction If an enormous number of calls are placed at the same time, well in excess of the capacity of an exchange, the exchange cannot perform switching normally. This function restricts outgoing calls by rejecting them, except some calls which must be established.

Incoming call restriction If the number of waiting incoming calls increases as in the case of outgoing call restriction, the exchange cannot perform normal switch operation. This function restricts incoming calls by rejecting them from other exchanges.

Originating connection restriction If growing traffic to a certain area or subscriber causes congestion that affects calls to other areas or subscribers, this function restricts calls to that area or subscriber to prevent the congestion from affecting the entire network.