the control circuit causes the transmission surfaces of 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, {HEAD ~ the ultrasonic wave} with {TAIL ~ a third directivity} is transmitted from the transmission surfaces of the second combination of transmission elements 
the control circuit causes the transmission surfaces of 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 , { HEAD ~ the ultrasonic wave } with { TAIL ~ a third directivity } is transmitted from the transmission surfaces of the second combination of transmission elements
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