| 摘要 |
PURPOSE:To enable the user to wait while viewing the focusing of fish groups on the image plane at the same spot by modulating the luminance of a cathode ray tube with the reception pulses corresponding to the transmission pulses synchronized with the synchronizing signal for immobilizing of TV images. CONSTITUTION:The output signal E of a vertical output circuit 3 of a TV receiver A is differentiated and is supplied as a signal F to a resonance circuit connected to the emitter of a transistor TR. The resonance frequency of the magnetostrictive element D of an electromagnetic type ultrasonic transducer B is emitted into water. The respective reflected waves (e) and (f) from a fish group 9 and the ground bottom 8 are applied to a video ampllfier 1 via the transducer B driven synchronously with the vehicle synchronizing signal and are further applied to a cathode ray tube 1, so that the electron beam thereof is luminance modulated. In this case, the raster parts corresponding to the duration period of the reflected waves are luminance modulated. |
