Acoustical well logging

Claim 1

A SYSTEM FOR PRODUCING AN ACOUSTICAL LOG OF SUBSURFACE STRATA TRAVERSED BY A BOREHOLE WHICH COMPRISES AN EXPLORING UNIT, MEANS FOR MOVING SAID EXPLORING UNIT THROUGH SAID BOREHOLE, MEANS OPERATIVELY ASSOCIATED WITH SAID EXPLORING UNIT FOR PERIODICALLY PRODUCING ACOUSTIC PULSES FOR TRAVEL THROUGH THE SUBSURFACE STRATA, MEANS OPERATIVELY ASSOCIATED WITH SAID EXPLORING UNIT FOR PRODUCING FIRST AND SECOND ELECTRIC PULSES SEPARATED FROM ONE ANOTHER BY A TIME INTERVAL INDICATIVE OF THE TIME OF TRAVEL OF EACH OF SAID ACOUSTIC PULSES BETWEEN TWO POINTS ON SAID EXPLORING UNIT SPACED APART A PREDETERMINED DISTANCE, A TRANSMISSION LINE, MEANS OPERATIVELY ASSOCIATED WITH SAID EXPLORING UNIT FOR APPLYING SAID FIRST AND SECOND PULSES TO ONE END OF SAID TRANSMISSION LINE, PULSE SEPARATING MEANS COUPLED TO THE OPPOSITE END OF SAID TRANSMISSION LINE FOR PRODUCING AT A FIRST OUTPUT THEREOF EACH OF SAID FIRST PULSES AND AT A SECOND OUTPUT THEREOF EACH OF SAID SECOND PULSES, A FIRST NORMALLY CLOSED GATE HAVING A FIRST INPUT COUPLED TO THE FIRST OUTPUT OF SAID PULSE SEPARATING MEANS AND A FIRST BISTABLE MULTIVIBRATOR HAVING AN OUTPUT COUPLED TO A SECOND INPUT OF SAID FIRST GATE, MEANS OPERATIVELY ASSOCIATED WITH THE MEANS FOR MOVING SAID EXPLORING UNIT THROUGH SAID BOREHOLE AND RESPONSIVE TO THE DEPTH OF SAID UNIT IN THE BOREHOLE FOR APPLYING A TRIGGER PULSE TO SAID FIRST BISTABLE MULTIVIBRATOR EACH TIME THAT SAID EXPLORING UNIT MOVES A DISTANCE EQUAL TO SAID PREDETERMINED DISTANCE, A SECOND BISTABLE MULTIVIBRATOR HAVING A FIRST INPUT COUPLED TO THE OUTPUT OF SAID FIRST GATE, MEANS COUPLED TO THE OUTPUT OF SAID SECOND BISTABLE MULTIVIBRATOR FOR DIFFERENTIATING THE OUTPUT OF SAID SECOND BISTABLE MULTIVIBRATOR, MEANS FOR COUPLING THE OUTPUT OF SAID DIFFERENTIATING MEANS TO SAID FIRST BISTABLE MULITVIBRATOR, MEANS FOR COUPLING THE SECOND OUTPUT OF SAID PULSE SEPARATING MEANS TO A SECOND INPUT OF SAID SECOND BISTABLE MULITVIBRATOR, A SECOND NORMALLY CLOSED GATE HAVING AN INPUT COUPLED TO THE OUTPUT OF SAID SECOND BISTABLE MULTIVIBRATOR, AN OSCILLATOR COUPLED TO A SECOND INPUT OF SAID SECOND GATE, AND A RECORDING DEVICE COUPLED TO THE OUTPUT OF SAID SECOND GATE.