PURPOSE: To switch and connection-control a repeating line while the connecting condition of a matrix switching part is being grasped at any time by preparing connecting condition information to indicate the connecting condition of the repeating line, comparing it with new connecting data from a central control part, and switching-controlling only a different connecting point.

CONSTITUTION: Repeating lines 23 and 24 are connected to a matrix switching part 22 of a line connecting device 21, a line connecting condition information preparing part 25 is connected to a memory part 30, connecting condition information 31 of the matrix switching part 22 after a switching action prepared based on switching connection condition information 29 from a data input part 28 is prepared, and it is stored into the memory part 30. Connecting data as line switching/connection information 16 from a central control part 15 are inputted to a control part 32 of a line connecting part 21, the control part 32 reads the date of the line connecting condition after the previous switching from the memory part 30, and they are compared with the new switching data. When the both data correspond, the switching action of the connecting point is not executed, and the switching-control is executed for the other new connecting point. After the completion of the switching action, the connecting data prepared in the same way as the last time is stored into the memory part 30.