PURPOSE: To improve the reliability of a terminal device, by counting the using time, the working frequencies, etc. of the expendable parts such as a CRT, a rubber roller, etc. and delivering these count values to a center with a command of the center to recognize accurately the lifetime of the expendable parts when necessary and then to exchange them.

CONSTITUTION: A display device 6 is connected to a center 1 containing an electronic computer, etc. to be used as a terminal device. Then a control part 7 through which the data is tansferred between the center 6 and the device 6 is provided to the device 6 along with a cathode-ray tube 4 and an electric power supply part 5. A counter 8 is set between the device 6 and the part 5 to count the using time of the tube 4, and this count value is informed when necessary to the center 1 from the part 7 by a command given from the center 1. Then the using time of the expendable parts lincuding the tube 4, a rubber roller, etc. which are used at the device 6 is informed to the center 1. Thus the lifetime of the expandable parts is accurately recognized, and the reliability is improved for a terminal device.