An object of the invention is to prevent a human error, greatly reducing man-hours and to securely identify a core. To achieve the object, a request for a serial number is first made via a conductor of a core from a recognition unit that functions as a master to a recognition unit that functions as a slave. Next, the recognition unit as the slave reads a serial number for an IC tag and transmits the serial number via the conductor of the core. The recognition unit as the master receives the serial number transmitted from the recognition unit as the slave and collates the serial number and a serial number stored in an IC tag. It is ascertained by the collation that the conduction of the core is correctly made and it is displayed on a display of the recognition unit as the master and others that no disconnection on the way and no error in selecting an end of wiring are caused.