the control circuit causes {HEAD ~ the transmission surfaces} of {TAIL ~ the second combination} of transmission elements to vibrate in a substantially same phase so that the transmission surfaces of the second combination vibrate in an integral manner, and thereby, the ultrasonic wave with a third directivity is transmitted from the transmission surfaces of the second combination of transmission elements 
of
the control circuit causes { HEAD ~ the transmission surfaces } of { TAIL ~ the second combination } of transmission elements to vibrate in a substantially same phase so that the transmission surfaces of the second combination vibrate in an integral manner , and thereby , the ultrasonic wave with a third directivity is transmitted from the transmission surfaces of the second combination of transmission elements
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL 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