| 摘要 |
PROBLEM TO BE SOLVED: To display an interference wave on a monitor when a fish finder of one's own ship receives a transmission signal issued by the another ship operating nearby. SOLUTION: In the submergible finder where an ultrasonic wave is transmitted at a specific time interval in the downward direction of one's own ship, and every time when receiving an echo equivalent to one transmission, it is displayed in a vertical directional one line on one end of the monitor by a color or a shade according to the reception level, and the past display is shifted one line by one line to the other end side according to this display, a frequency of a transmission pulse supplied to an echo sounder transducer is changed, a frequency of a local signal is also changed so that a difference frequency obtained by a frequency converting circuit 42 in a receiving part becomes constant, and only a signal of the difference frequency is selected by a filter 43.
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