Echo sounding apparatus for recording sonar echoes of greatly varying amplitudes

Claim 1

SONAR APPARATUS, COMPRISING A TRANSDUCER FOR TRANSLATING RECEIVED SONIC ECHOES TO ECHO VOLTAGE, A RECORDER FOR PRODUCING ECHOGRAMS ON ELECTRICALLY SENSITIVE RECORDING PAPER, EACH OF SAID ECHOGRAMS COMPRISING A PLURALITY OF SPACED SUBSTANTIALLY PARALLEL LINES EACH REPRESENTING ONE RECORDING CYCLE OF SAID RECORDER AND EACH INCLUDING A CONTOUR PORTION OF DETERMINED LENGTH REPRESENTING THE BOTTOM OF A BODY OF WATER AND AN ADDITIONAL PORTION REPRESENTING FLOATING OBJECTS IN THE BODY OF WATER, AND AN AMPLIFIER CONNECTING SAID TRANSDUCER TO SAID RECORDER FOR APPLYING RECORDING VOLTAGE TO THE PAPER IN RESPONSE TO SAID ECHO VOLTAGE, AN ELECTRONIC VOLTAGE CONTROL DEVICE CONNECTED BETWEEN SAID AMPLIFIER AND SAID RECORDER AND HAVING A PLURALITY OF ELECTRONICALLY VARIABLE RESISTANCE MEANS CONNECTED IN PARALLEL RELATION TO THE PAPER RESISTANCE OF SAID RECORDER, SAID RESISTANCE MEANS HAVING RESPECTIVE INPUT MEANS CONNECTED TO SAID AMPLIFIER FOR RESPONSE TO THE ECHO VOLTAGE AND EACH OF SAID RESISTANCE MEANS HAVING ONE VOLTAGE THRESHOLD VALUE CORRESPONDING TO A GIVEN ECHO AMPLITUDE IN THE LOW-AMPLITUDE PORTION OF THE TOTAL RECEIVABLE AMPLITUDE RANGE, EACH OF THE THRESHOLD VALUES BEING DIFFERENT FROM THE OTHERS, SO AS TO REDUCE BY ONE OF SAID RESISTANCE MEANS, WHEN SAID ECHO VOLTAGE IS ABOVE THE THRESHOLD VALUE OF SAID ONE OF SAID RESISTANCE MEANS, THE RECORDING VOLTAGE TO BELOW THE ONE OBTAINING AT SAID GIVEN ECHO AMPLITUDE THEREBY CONSIDERABLY SHORTENING THE DETERMINED LENGTH OF THE CONTOUR PORTION OF EACH LINE OF SAID ECHOGRAM TO CONSIDERABLY INCREASE THE RATIO OF THE LENGTH OF THE ADDITIONAL PORTION OF EACH SAID LINE TO SAID DETERMINED LENGTH OF EACH SAID LINE SO THAT A CONSIDERABLY GREATER CONTRAST IS PROVIDED BETWEEN SAID ADDITIONAL AND CONTOUR PORTIONS AND THEREFORE BETWEEN SAID FLOATING OBJECT REPRESENTATIONS AND SAID BOTTOM REPRESENTATIONS.