Patent ID: 7536010

Claim:
An exchange system which includes a plurality of button telephone sets having a plurality of function keys equipped with light emitting device, respectively, and an exchange to house the button telephone sets via a communication line, wherein the exchange comprises: a failure detection unit which detects failures in the exchange system; a failure information table which stores detailed information on the failures detected by the failure detection unit; a table of notification destinations for each failure, which stores notification destinations of the detected failures; a failure determining unit which determines the notification destinations of the detected failures by referring to the table of the notification destination for each failure; a first alarm key table in which the function keys are associated with the respective button telephone sets for each type of the failures; an alarm key retrieval unit which retrieves positions of the function keys displaying failure states from the first alarm key table in response to the button telephone sets of the failure notification destinations; a failure notification unit which notifies the failures to the button telephone sets; a transmission unit which transmits data from the failure notification unit to the button telephone sets of the failure notification destinations; a key operation receiving unit which receives key operation information from the button telephone sets to transfer the key operation information to a first alarm key setting unit and the failure notification unit; a second alarm key setting unit which assigns alarm keys displaying the failure states onto specified function keys of specified button telephone sets on the basis of the information received from the key operation receiving units; and a second alarm key table which stores the assignment of the alarm keys, and wherein each of the button telephone sets comprises: a display device to display character information; a failure information receiving unit to receive data from a transmission unit for button telephone sets of the exchange; a display determining unit to determine display types of the function keys from types of the received data; a light emitting device control unit to display-controlling light emitting devices of the corresponding function keys in response to an instruction from the display determining unit; a display device control unit to perform a data display onto the display device in accordance with the instruction from the display determining unit; a key operation determining unit to determine depressed states of keys of the button telephone sets including the function keys; and a key operation transmission unit to transmit the depressed states of the keys to the exchange.