PURPOSE: To avoid the repetition of a communication processing as against a medium in a gate system by detecting the U-turn of an object to be detected inside a path.

CONSTITUTION: When a commutation ticket 21 reaches a communication possible area 12b constituted by an antenna 2b by way of a reception possible area 12a constituted by the antenna 2a, data is transmitted and received between the commutation ticket 21 and an automatic ticket-examining machine 1. After this, when the user executes U-turn inside the path so that the commutation ticket re-enters inside the communication possible area 12a constituted by the antenna 2a, it is judged that the user having the commutation ticket 21 executes U-turn so as to turn off the entrance pit of the communication ticket 21, which is once turned on.