PURPOSE: To obtain the optimum and inexpensive maintenance equipment to be prepared by the user for the maintenance by providing a console displaying an acknowledge with respect to an inquiry and an emergency message notifying devices in each exchange.

CONSTITUTION: When any fault takes place in any of exchanges 1a-1d, the maintenance or operation manager of the faulty exchange uses various function such as a state display function, a control function, a test function, a data setting function and a data collection function integrated in the exchanges and maintenance consoles 5a-5d and locates a fault caused around the exchange based on contents of various acknowledge displays with respect to the inquiry operation of the maintenance console connected to the exchange and a fault state for the occasion. Furthermore, as to a fault of each of the exchanges 1a-1d or a line fault in each of relay lines 2ab-2cd to be handled on emergency, each exchange provides an automonous output to emergency message notifying equipments 6a-6d as an emergent notified message or an alarm to allow the manager to confirm the fault state in details by the operation of the maintenance console.