Patent GB-631199-A (GB)
Title: Improvements in or relating to pulsed echo sounders and like sub-aqueous distance measuring apparatus
IPC: G01S1/72
Filed: 1947-02-20
Abstract: 631,199. Echo - sounding and distancemeasuring apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and GRAY, T. Feb. 20, 1947, No. 5042. [Class 118 (ii)] In a pulsed echo sounder or the like of the kind in which the echo actuates an indicator rotated a plurality of times during each pulse period range-selection means is provided for co-related selection of the revolution during which the indicator is operative and of the appropriate one of a plurality of series of indicia indicating depth or distance. A neon lamp indicator (not shown) rotates four times per pulse period behind a transparent scale S, Fig. 3, in a mask M having windows W through which depth indications R may be seen. Five sets of these figures are on a disc which may be manually rotated so that one of the ranges 0-130, 100-230, 200-330, 300-430 or 400- 530 fathoms is seen through the windows W. The rotation of this disc also rotates two ganged five-position range switches 1RS, 2RS to the appropriate position. These switches, Figs. 1 and 2 are connected to motor-driven cam-operated switches 1C, 2C, 3C. During the first rotation of the neon lamp during each pulse period the transmitter cam-switch 3C partially prepares the pulsing circuit and camswitch 2C further momentarily prepares this circuit at 0, 120 and 240 degrees during each revolution of the neon lamp, the particular position during the first revolution of the lamp in each pulse period at which a pulse is transmitted being determined by the setting of the range switch 2RS. A pulse can thus be emitted only when the neon lamp is at the beginning of its first rotation.in a pulse period or <SP>1</SP>/ 3  or <SP>2</SP>/ 3  revolution later. A receiver cam-switch 1C prepares the receiver circuit during each lamp rotation in turn, the particular rotation during which the circuit is completed being determined by the range switch 1RS. The receiver therefore becomes operative for one revolution of the neon lamp, either at the commencement of a pulse period or 1, 2 or 3 lamp revolutions later. By suitable wiring of the range switch 1RS, 2RS it is arranged that when the switch is in position 1 and the figures 0-130 fathoms are visible in the windows W a pulse is emitted at the beginning of the neon lamp's rotation and the receiver is effective during the first revolution, i.e. during the time it takes a pulse to travel 150 fathoms and return. The figure illuminated by the neon lamp when the echo returns will thus indicate the distance of the reflecting object with the range switch in position 2, the range figures 100-230 are visible and a pulse is emitted <SP>2</SP>/ 3  revolution (i.e. 100 fathoms) before the second revolution, during which the receiver is operative. An echo from an object between 100 and 230 fathoms will therefore illuminate the neon lamp. As the minimum range displayed increases to 200, 300 and 400 fathoms, the switch 1RS, 2RS in positions 3, 4 and 5 ensures that the transmitted pulse occurs 4/3, 6/3 or 8/3 revolution before the receiver becomes effective.