Echo-sounding apparatus for examining strata below the sea-bed with variable gain means responsive to sea-bed echoes

Claim 1

ECHO SOUNDING APPARATUS FOR EXAMINING STRATA BELOW TE SEA-BED COMPRISING TRANSMITTER MEANS FOR TRANSMITTING MECHANICAL-WAVE ENERGY TOWARDS THE SEA-BED, RECEIVER MEANS FOR RECEIVING ECHOES OF THE TRANSMITTED ENERGY TO DERIVE SIGNALS IN ACCORDANCE RESPECTIVELY WITH RECEIVED SEA-BED AND STRATA ECHOES, DISPLAY MEANS RESPONSIVE TO SAID SIGNALS TO PROVIDE A DISPLAY OF ECHOES RECEIVED BY THE RECEIVER MEANS, AND SUPPRESSION MEANS FOR ATTENUATING THE SEA-BED ECHO-SIGNAL RELATIVE TO THE STRATA ECHOSIGNALS, SAID SUPPRESSION MEANS COMPRISING A CONTROLLABLE-GAIN AMPLIFIER COUPLED BETWEEN SAID RECEIVER MEANS AND SAID DISPLAY MEANS FOR PASSING SAID SIGNALS DERIVED BY SAID DISPLAY MEANS TO SAID DISPLAY MEANS, AND CONTROL MEANS FOR CONTROLLING THE AMPLIFIER-GAIN TO INCREASE FROM A LOW VALUE DURING PASSAGE THROUGH THE AMPLIFIER OF THE SEA-BED ECHO-SIGNAL TO A HIGHER VALUE DURING PASSAGE THROUGH THE AMPLIFIER OF THE IMMEDIATELY-FOLLOWING STRATA ECHO-SIGNALS, SAID CONTROL MEANS INCLUDING FIRST MEANS TRIGGERABLE TO SUPPLY A PREDETERMINED CONTROL SIGNAL HAVING AT LEAST A PORTION THEREOF THAT CHANGES AS A PREDETERMINED FUNCTION OF TIME FROM A FIRST VALUE TO A SECOND VALUE, SECOND MEANS RESPONSIVE TO RECEPTION OF THE SEA-BED ECHO BY SAID RECEIVER MEANS TO TRIGGER SAID FIRST MEANS TO SUPPLY SAID CONTROL SIGNAL, AND THIRD MEANS COUPLED TO THE AMPLIFIER TO INCREASE THE AMPLIFIER-GAIN IMMEDIATELY FOLLOWING PASSAGE THROUGH THE AMPLIFIER OF SAID SEA-BED ECHO-SIGNAL, SAID THIRD MEANS BEING RESPONSIVE TO SUPPLY OF SAID CONTROL SIGNAL BY SAID FIRST MEANS TO INCREASE SAID AMPLIFIER-GAIN IN ACCORDANCE WITH CHANGE IN SAID CONTROL SIGNAL FROM SAID FIRST VALUE TO SAID SECOND VALUE.