To prevent artificial setting mistake or the like by containing an electronic circuit package having an auxiliary function without any notice in the case of containing the electronic circuit package into the electronic circuit unit.

The worker contains a master package at a slot end of the electronic circuit unit and the electronic circuit packages 6 by a required line number are contained. At application of power, a discrimination circuit 10 of each electronic circuit package 6 reads a physical number from each slot storage section 11 and stores it tentatively in the discrimination circuit 10 and a physical number is sent to a contention line 9. Then a physical number closest to 0 is selected in the contention line 9 and the physical number is returned to each discrimination circuit 10. Each discrimination circuit 10 compares the returned physical number with the physical number stored tentatively before and when they are coincident, the auxiliary function is automatically activated.