Patent GB-1061954-A (GB)
Title: Improvements in or relating to echo sounding apparatus
IPC: H04B11/00
Filed: 1964-06-26
Abstract: 1,061,954. Echo sounding apparatus. ATLASWERKE A.G. June 26, 1964 [June 29, 1963], No. 26565/64. Heading H4D. [Also in Division G3] In echo sounding apparatus of the type wherein the transmitting and receiving transducers are mounted on the fishing net, separate from the ship and an indicating device, measuring results, together with necessary synchronizing signals, are fed from the transducers to the ship by means of a distinguishably modulated sound wave. Two trains of synchronizing pulses may be provided, one being for fine control of the indicating device and the other being for coarse control thereof. The remote transducer means comprises, Fig. 1, a pulses generator 6, producing a rapid train of pulses (U1), Fig. 3a (not shown). These are given a characteristic width in a first generator 8, and are fed as train (U5) to frequency modulate the output of generator 4. Train (U1) is also fed to frequency divider 7 to produce train (U2) which is used to trigger the transmit/receive transducer 1. Train (U2) is also passed to a second generator 9 where the pulses are given a characteristic width and are passed on as pulses (U6) to frequency modulate generator 4. Echo pulses (U7) from the transducer 1 and receiving amplifier 3 are also used to frequency modulate generator 4. The output of generator 4, frequency modulated with the echo signals and the two synchronizing pulse trains, is fed to a transducer 5 for transmission to the ship. The signal is received at the ship by transducer 10, Fig. 2, and the various pulses separated out after demodulation by filter 13, the echo pulses being shown as (U10), Fig. 3b (not shown), the coarse synchronizing train as (U9) and the fine synchronizing train as (U8). The echo pulses are fed to an echograph, comprising a chart 16 and a stylus 15, carried on a belt 17 controlled by a motor 20 such that the stylus travels down the chart, ideally in synchronism with transmission of pulses (U3) by transducer 1. The coarse synchronizing pulses (U9) are converted into pulses (U19), Fig. 3b, in pulse shaper 38 and each pulse thereof used to stop the pulse output of a bi-stable multivibrator 37. The multivibrator pulses are started by pulses (U17) from a cam switch operated in synchronism with the movement of stylus 15. When synchronism is achieved between the movement of stylus 15 and the transmission of the pulses by transducer 1, the stylus makes a mark on datum line 22 on the chart, simultaneously with a pulse being transmitted. In this synchronized state the pulses (U17) are midway between pulses (U19). The output of the multivibrator (U18) is integrated in Miller integrator 39 to give waveform (U20). The peak valve of the waveform representing the duration of the multivibrator output and the position in time of (U17) is stored in storage condenser 40 to give waveform (U21). The stored peak valve is compared with a voltage level (U22) from voltage source 42, during a time tv as defined by the width of pulse (U23), and the result, which would be zero in the case of exact synchronism, is used to adjust the speed of the motor 20 to obtain synchronism. The fine synchronizing pulses (U8) provide synchronizing signals for the motor in the same manner. When pulse (U17) is more than half the spacing of pulses U8 from its synchronous position midway between the pulses U9, the fine synchronizing pulses are not able to bring the motor 20 into synchronizing and so are blocked by gate 33 under the control of a comparator stage 45 determining when the peak valve of waveform (U21) is outside the region bounded by the levels (U23MAX) and (U23MIN).