PRIVATE BRANCH EXCHANGE SYSTEM

PROBLEM TO BE SOLVED: To provide a private branch exchange system for guaranteeing telephone communication by switching to another private branch exchange when the entire private branch exchange fails.SOLUTION: The private branch exchange system includes a first private branch exchange, a second private branch exchange and a switching device. When receiving a switching request from the first private branch exchange or the second private branch exchange, the switching device transmits standby information to the first private branch exchange under operation, transmits operation information to the second private branch exchange on standby, and changes the connection destination of a telephone network and an extension terminal to the second private branch exchange.