PURPOSE: To minimize data loss at the time of inserting a new station into a transmission line by outputting a cutoff command signal to a first interrupting means and outputting a continuity command signal to a second interrupting means at the same time by a control means after the control means outputs a connection command signal.

CONSTITUTION: When an operator inputs a trigger signal, a pulse signal output part 11 of a new station control circuit 10 generates a pulse signal and outputs the pulse signal to a gate 6, driving coils 81d and 82d of a connecting circuit 8, and a delay signal generating part 12. The gate 6 opens its gate, and the circuit 10 switches from a break contact to make contacts 81c and 82c and connects a transmission line 4 and a new station A. Consequently, the connection is executed after the gate is opened. The generating part 12 generates a signal obtained by delaying the pulse signal for prescribed time and outputs the signal to the respective input terminals of a gate 5 and a gate 7. While the gate 7 closes its gate, the gate 5 opens its gate. Namely, the new station A is not inserted into a transmission line L in a trigger signal inputting stage and inserted into the transmission line L in a delay pulse inputting stage.