Apparatus for recording received echoes

Claim 1

APPARATUS FOR RECORDING ECHO SIGNALS ON RECORDING PAPER ADAPTED TO CHANGE VISIBLY UPON THE PASSAGE OF A CURRENT DUE TO AN APPLIED VOLTAGE, VALUES OF SAID APPLIED VOLTAGE VARYING OVER A RANGE SPECIFIC TO SAID PAPER PRODUCING VARYING DEGREES OF CONTRAST GRADED FROM ZERO RECORDED INTENSITY TO MAXIMUM RECORDED INTENSITY OF SAID RECORDING PAPER, COMPRISING MEANS FOR RECEIVING SAID ECHO SIGNALS AND DERVING A VOLTAGE THEREFROM, A FIRST CHANNEL INCLUDING MEANS FOR AMPLYFING SAID VOLTAGE, VOLTAGE LIMITING MEANS CONNECTED TO SAID AMPLIFYING MEANS TO LIMIT SAID VOLTAGE TO A PREDETERMINED LEVEL AND CAUSE SAID FIRST CHANNEL WHEN LIMITING SAID VOLTAGE TO PROVIDE A FIRST COMPONENT OF SAID APPLIED VOLTAGE SUFFICIENT TO PRODUCE A RECORDED INTENSITY GREATER THAN SAID ZERO AND LESS THAN SAID MAXIMUM INTENSITY, A SECOND CHANNEL INCLUDING CIRCUIT MEANS FOR DIFFERENTIATING SAID DERIVED VOLTAGE, TO PROVIDE A SECOND COMPONENT OF SAID APPLIED VOLTAGE, MEANS FOR ALGEBRICALLY COMBINING SAID FIRST AND SECOND COMPONENTS TO PROVIDE SAID APPLIED VOLTAGE TO SAID RECORDER, MEANS FOR COUPLING SAID APPLIED VOLTAGE TO SAID RECORDER, SAID PREDETERMINED LEVEL BEING SUCH AS TO LIMIT THE RECORDED INTENSITY CAUSED BY THE OUTPUT OF THE FIRST CHANNEL TO BELOW SAID MAXIMUM RECORDED INTENSITY.