| 摘要 |
PURPOSE:To reduce the frequency of use of a telephone line for check by constituting an information forward transmission path of a terminal equipment, sending a check signal sent from a supervisory center to the lowermost terminal equipment from the uppermost terminal equipment sequentially and outputting a replay signal from the lowest-order terminal equipment to the supervisory center. CONSTITUTION:When a supervisory center 10 sends a check signal to uppermost terminal equipments 1-1-m-1 of sets 1-m respectively via telephone lines 9, 9a, the signal is sent sequentially from the uppermost terminal equipment to the lowermost terminal equipments 1-n-m-n according to prescribed information transmission order. The lowermost terminal equipment sends the notice signal to the center 10 when the check signal is reached. The center 10 confirms its normality in the presence of the notice signal. When the notice signal does not come even after a prescribed time elapses, the check signal is sent individually to the set of the terminal equipments for the checking. Thus, the frequency of use of the telephone line for the check is reduced. |
