a signal transmission mechanism configured to transmit {HEAD ~ a first signal} in {TAIL ~ a case} that a height of the free end portion is lower than a reference position which is set at a position higher than the stand by position, and to transmit a second signal which differs from the first signal, in a case that the height of the free end portion is not less than the reference position 
a signal transmission mechanism configured to transmit { HEAD ~ a first signal } in { TAIL ~ a case } that a height of the free end portion is lower than a reference position which is set at a position higher than the stand by position , and to transmit a second signal which differs from the first signal , in a case that the height of the free end portion is not less than the reference position
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH