| 摘要 |
PURPOSE:To stabilize the expanding motion of the amplitude of display of a display unit and thereby make accurate detection of shchools of benthic fish, by catching only bottom-reflected waves of reflected waves to measure and display the depth of the sea bottom. CONSTITUTION:Reflected waves from the sea bottom or the like are given to a display unit 6 via a wave transmitter-receiver 4, a switching circuit 3 and a receiver 5. At this time, a part of reflection signals is introduced into a sensitive- time controlling amplifier 7 and an output delivered when the bottom-reflection signal is maximum is given to an AGC circuit 8. The output of the circuit 8 is shaped 8 and supplied to a pulse checking circuit 10. At the circuit 10, pulses whose difference in time from a transmitted timing pulse is received successively at plural times at an identical position are selected out of received pulses. When the output pulse of the circuit 10 is only one, this one pulse represents a signal reflected from the sea bottom. This pulse fixes a gain of AGC8 and is stored in a hold circuit 11. The depth of the sea bottom is displayed digitally by a sea- bottom depth display circuit 12 and further a bottom lock signal is given to a display unit 6. |
