| 摘要 |
1509441 Echo sounders LAITRAM CORP 20 March 1975 [21 March 1974] 11635/75 Heading G1G A depth echo sounder has a receiver (14) Fig. 1 (not shown) and a processor (18) shown in Fig. 3, which processor discriminates between spurious and true bottom echoes, both echoes being above a predetermined level, and gives an indication of the depth. The processor 32-50 receives a train of pulses, Fig. 4A (not shown), from the receiver (14) each pulse corresponding to an echo, the width of the pulse depending on the duration of the echo above a predetermined threshold. An initial pulse from the slow clock 42 launches an acoustic pulse and resets down counter 44 and counter 34. If down counter is not at zero, gate 50 passes the modulated pulses representing the echoes. Each pulse passed by AND gate 50 transfers the count prevailing in counter 34 to memory 36 and down counter 44. The recycling through zero detector 46 and OR gate 48 provides a transient block to AND gate 50 as each zero is detected. This system prevents all spurious echoes and harmonics thereof from reaching memory 36. At the end of a pulse from clock 42, the updated number of counts stored is transferred to a digital display 63. The pulse width modulated pulses from the receiver (14) can be used directly to give an analogue depth display in which LED 62 is illuminated at an angle of rotation of disc 60 corresponding to depth.
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