Apparatus for measuring travel time of seismic waves from the earth's surface to a given depth in the earth

Claim 1

APPARATUS FOR MEASURING TRAVEL TIME OF SEISMIC WAVES BETWEEN AN ELECTRO-SEISMIC WAVE TRANSDUCER MEANS AT THE EARTH''S SURFACE FOR PRODUCING CONTINUOUS WAVE SEISMIC SIGNALS VARIABLE IN AMPLITUDE IN ACCORDANCE WITH VARIATIONS IN THE AMPLITUDE OF ACTUATING ELECTRICAL SIGNALS CONNECTED THERETO, AND A GEOPHONE IN A BOREHOLE IN THE EARTH, COMPRISING: TERMINAL MEANS FOR CONNECTION TO SAID GEOPHONE; SEISMIC WAVE DETECTOR MEANS FOR POSITIONING IN THE IMMEDIATE VICINITY OF SAID TRANSDUCER MEANS TO PRODUCE ELECTRICAL SIGNALS INDICATIVE OF SEISMIC WAVES INJECTED INTO THE EARTH BY SAID TRANSDUCER MEANS; RECORDING AND REPRODUCING MEANS FOR PRODUCING A TIMING PULSE TRAIN IN A FIRST SIGNAL CHANNEL THEREOF, PRODUCING A PSEUDO-RANDOM ELECTRICAL SIGNAL IN A SECOND SIGNAL CHANNEL THEREOF FOR DRIVING SAID TRANSDUCER MEANS, RECORDING AND REPRODUCING ELECTRICAL SIGNALS IN THIRD, FOURTH, AND FIFTH SIGNAL CHANNELS THEREOF, PRODUCING A TIME REFERENCE PULSE AT THE BEGINNING OF AN ELECTRICAL SIGNAL REPRODUCING CYCLE; CORRELATING MEANS HAVING FIRST AND SECOND INPUT CIRCUITS AND AN OUTPUT CIRCUIT, FOR PRODUCING A SIGNAL IN SAID OUTPUT CIRCUIT HAVING AN AMPLITUDE THAT IS VARIABLE IN ACCORDANCE WITH THE DEGREE OF CORRELATION BETWEEN ELECTRICAL SIGNALS FED TO SAID FIRST AND SECOND INPUT CIRCUITS THEREOF; MEANS SELECTIVELY CONNECTING SAID THIRD SIGNAL CHANNEL TO SAID DETECTOR MEANS AND TO SAID FIRST INPUT CIRCUIT OF SAID CORRELATING MEANS, SELECTIVELY CONNECTING SAID FOURTH SIGNAL CHANNEL TO SAID TERMINALS MEANS FOR RECORDING SAID GEOPHONE SIGNALS, AND TO SAID SECOND INPUT CIRCUIT OF SAID CORRELATING MEANS FOR FEEDING PREVIOUSLY RECORDED REPRODUCED SIGNALS TO SAID CORRELATING MEANS, AND SELECTIVELY CONNECTING SAID FIFTH SIGNAL CHANNEL TO SAID CORRELATING MEANS OUTPUT CIRCUIT FOR RECORDING THE OUTPUT SIGNALS OF SAID CORRELATING MEANS; SAID RECORDING AND REPRODUCING MEANS BEING ADAPTED TO PRODUCE AN OUTPUT PULSE IN SAID FIFTH SIGNAL CHANNEL THEREOF ON A REPRODUCING CYCLE THEREOF AT A CORRELATION EXTREME OF THE SIGNAL RECORDED THEREIN; AND MEANS CONNECTED TO SAID RECORDING AND REPRODUCING MEANS FOR COUNTING THE NUMBER OF PULSES IN SAID TIMING PULSE TRAIN ON A REPRODUCING CYCLE THEREOF BETWEEN PRODUCTION OF SAID TIME REFERENCE PULSE AND PRODUCTION OF A SIGNAL IN SAID FIFTH SIGNAL CHANNEL INDICATIVE OF MAXIMUM DEGREE OF CORRELATION.