Patent GB-944816-A (GB)
Title: Improvements in or relating to echo sounders
Inventor: THOMAS ALAN JOHN
IPC: G01S15/89
Filed: 1961-02-27
Abstract: 944,816. Echo sounding. MARCONI SOUNDING DEVICE CO. Ltd. Nov. 1, 1961 [Feb. 27, 1961], No. 7067/61. Heading H4D. In an echo sounder comprising a transmitter 4 and a receiver 9 cooperating either with a single transducer 5 or with respective individual transducers, reflected echo signals, e.g. from the sea bed, fish shoals &c., are supplied via an amplifier 19 to the control grid 11 of the " writing " gun of a cathode-ray tube 7 the beam from this gun being scanned in co-ordinate directions such that a charge pattern corresponding to the echoes is formed on a storage electrode 15 which is continuously " flooded " by electrons from a second gun 14 to produce a display on the fluorescent screen 17 corresponding to the charge pattern. The vertical deflection of the " writing " beam has a repetition period of about 3 seconds and is produced by integrating in 3 the output of a multi-vibrator 2 which produces a square wave, preferably of 1 : 1 mark/space ratio, under the control of one in every eight pulses from a generator 1. By differentiation of this square wave and suppression of the positively going pulses a negatively going pulse is produced which controls the transmitter 4 and additionally triggers a monostable multivibrator 20 the positively going portion of the output of which is considerably longer than the negatively going portion and after integration in 21 provides the horizontal deflection of the " writing " beam with a repetition period of about 15 minutes. The termination of the horizontal deflection is controlled by a threshold detector 24 which in response to a predetermined amplitude of the sawtooth wave from integrator 21 triggers a pulse generator 25 the output from which resets multivibrator 20 and erases the charge on electrode 15. By arranging the amplitude of the erase pulse such that it only partially erases the charge and such that two pulses are required for complete erasure the display during one scan may be retained at lower intensity during the next succeeding scan. If it is desired to retain the displayed information at the end of one horizontal scan the output from 24 (instead of being supplied to generator 25) may be employed to inhibit multivibrator 2 and when erasure of the displayed information and the commencement of a new scan is required generator 25 may be arranged (by manual, e.g. push button, operation) to produce pulses which erase the stored information on electrode 15 and re-set multivibrators 2 and 20 (Fig. 2, not shown). When variable ranges are required the frequency of generator 1 and the parameters of multivibrator 2 and integrator 3 may be made adjustable. In an alternative arrangement a second " writing " gun the beam from which is  caused to scan the storage electrode slightly in advance of the beam from " writing " guns 10, 11 is employed to erase the charge pattern just before the " writing " of new information. Although the mark/space ratio of multivibrator 2 may have any convenient value the use of a 1 : 1 ratio prevents the display of " second-time echoes " when, as shown, the cathode 10 of the tube is supplied with a square wave derived by the differentiation in 18 of the vertical scanning wave such that the tube is " switched on " only during the occurrence of the negative halfcycles and the simultaneous application to the grid 11 of echo signals from the receiver 9. Pulses from generator 1 are also fed to grid 11 via amplifier 19 to draw depth markers across the display. Instead of employing a direct view storage tube the fluorescent screen may be replaced by a signal electrode from which signals are derived by electron beam scanning and then utilized to produce a display by means of a picture display tube.