First transmission information in which an optimum transmitting voltage and a transmitting waveform are associated with each other for each display mode, and second transmission information in which a plurality of transmitting voltage candidates and pulse-width modulation transmitting waveforms that are pulse-width-modulation controlled to respectively correspond to the plurality of transmitting voltage candidates are associated with each other for each display mode are used to extract a maximum transmitting voltage candidate that does not exceed an optimum transmitting voltage of a first display mode from a plurality of transmitting voltage candidates included in the second transmission information of a second display mode so as to determine a common transmitting voltage used in common for the first display mode and the second display mode based on the optimum transmitting voltage of the first display mode and/or the maximum transmitting voltage candidate.