When two electrical contacts with assembly, the locking arm is bent, so that the shorting terminal block 11, the bend and enter the detection of terminal non-contact state. Upon completion of the assembly, the locking arm 7 to return to their initial position, while the shorting terminal block 11 contacts with the detection terminal 8. The shorting terminal block of the first spring 15 and the second spring pieces 16. The second spring pieces 16 with the pressure parts 16b, the pressure can be locking arm 7 pressing this will cause the drive parts 16C slide along the first spring pieces 15, so as to exert pressure on neighboring contacts 15b of the local . In this way, can
shorting terminal block 11 increases the itinerary.