Patent GB-1177547-A (GB)
Title: Improvements in or relating to Echo Sounders.
Inventor: WHARAM EDWARD JAMES
IPC: G01S7/60
Filed: 1967-11-20
Abstract: 1,177,547. Echo sounding. MARCONI SOUNDING DEVICE CO. Ltd. 20 Aug., 1968 [2O Nov., 1967]. No. 52601/67. Heading H4D. In an echo-sounder in which echo signals are normally supplied to a recording device moving at a predetermined speed over a record surface, an expanded record of reflecting objects at different depths within a selected partial depth range is produced by differently delaying echo signals from those different depths by amounts which increase with said depths, and by utilizing the delayed signals to operate the recording device. In the Fig. 1 embodiment for providing a 6: 1 expansion of the 9 ft. zone above the sea-bed, echo signals normally pass via receiver R, threshold circuit E and circuit point Y to amplitude modulate a signal from oscillator MO for recording at S; they are also fed via delay unit D1 (delay equivalent to 9 ft. depth increment), amplifier A, shaping circuit D, detector DT and pulse shaper P (e.g. a Schmitt trigger) to circuit point X for application to first inputs of AND gates A1-A10. Circuit E responds to the strong sea-bed echo, provides a signal on line L for blocking the receiver R for the remainder of the sounding period, and provides a signal at Z for starting ring counter RC which then provides ten output pulses at a repetition period equivalent to a 1 ft. depth increment. These output pulses are the second inputs for gates A1-A10, so that the gates are enabled in turn and provide pulses at their outputs if echoes are received from 1 ft. wide depth zones in the 9 ft. zone above the sea-bed. The gate outputs (if any) trigger monostable circuits M1-M10 which return to their stable state after delay times respectively equivalent to 3 ft., 3 + 6 = 9 ft., 3 + 12 = 15 ft., ... , 3 + 54 = 57 ft. The trailing edges of the monostable outputs are detected by circuits S1-S10 (e.g. differentiators) and trigger pulseshapers P1-P10 (e.g. Schmitt triggers) whose outputs are fed to oscillator MO for recording. S is a paper strip recorder and the expanded record of the 9 ft. zone is recorded below the sea-bed line on a normally unused part of the paper. The common 3 ft. delay component of the monoafcables M1-M10 ensures that recording starts below the sea-bed line, whose width is assumed to correspond to 3 ft. on the depth scale. The expanded recording may be locked to some depth point other than the sea-bed, by closing switch SW to apply a high amplitude signal from SS to threshold circuit E. In the Fig. 2 embodiment, a clock signal source CS, 6:1 1 frequency-divider DV, shift register SR and electronic switches Sl, S2 (with control SCD) replace the Fig. 1 components RC, A1-A10, M1-M10, S1-S10 and P1- P10. Echo signals from circuit point Y are normally fed via S2 to oscillator MO for recording, and delayed echo signals (9 ft. delay) from circuit point X are clocked into register SR by normal rate clock pulses fed over S1. When SCD is actuated e.g. by the sea-bed echo trigger signal at Z the switches change over and the echo signals from the 9 ft. depth zone above the sea-bed are clocked out of register SR at onesixth normal rate and are applied to oscillator MO for recording.