| 摘要 |
PURPOSE:To prevent a reflected wave from a school of fish from being disabled to be discriminated owing to a sea-bottom reflected wave, by directing a receiver to the bottom the sea a specified time after an ultrasonic wave pulse is transmitted. CONSTITUTION:The direction of a transmitter and receiver 5 is controlled by an elevation angle control circuit 10 a specific time after an ultrasonic wave pulse is transmitted. This control is performed by driving a control motor 11. On the basis of the set angle of an elevation angle setter and set distance 9, the direction control by the control circuit 10 is performed by driving the control motor 11 so that when a coincidence circuit 8 generates a coincidence output, the direction of the transmitter and receiver 5 is set to the surface of the sea. Under said control, a reflected wave from a school of fish is discriminated clearly against a reflected wave from the bottom of the sea. |
