Detonation of seismic charges

Claim 1

APPARATUS FOR ENERGIZING AN ELECTRICALLY ACTUABLE FIRING CAP POSITIONED AT A GIVEN DEPTH IN A BOREHOLE RESPONSIVE TO DETECTION THEREBY OF ACOUSTIC WAVES OF PREDETERMINED MINIMUM AMPLITUDE GENERATED BY DETONATING AN EXPLOSIVE CHARGE IN THE BOREHOLE ABOVE SAID GIVEN DEPTH, COMPRISING: FIRST AND SECOND TERMINALS AT SUBSTANTIALLY SAID GIVEN DEPTH IN THE BOREHOLE TO WHICH SAID FIRING CAP IS TO BE CONNECTED, AND A THIRD TERMINAL; A STORAGE CAPACITOR IN THE BOREHOLE; MEANS CONNECTING SAID STORAGE CAPACITOR BETWEEN SAID FIRST AND THIRD TERMINALS SO THAT SAID STORAGE CAPACITOR CAN BE ELECTRICALLY CHARGED THROUGH THE CAP BY AN ELECTRICAL SOURCE AT THE EARTH''S SURFACE CONNECTED TO SAID FIRST AND THIRD TERMINALS THROUGH ELECTRICAL LEADS SEVERABLE BY SAID EXPLOSIVE CHARGE POSITIONED ABOVE SAID GIVEN DEPTH; MONOSTABLE MULTIVIBRATOR MEANS INCLUDING A NORMALLY CONDUCTIVE INPUT STAGE AND A NORMALLY NONCONDUCTIVE OUTPUT STAGE ADAPTED TO SWITCH CONDUCTION STATES WHEN AN ACTUATING SIGNAL IS APPLIED TO SAID INPUT STAGE, SAID OUTPUT STAGE BEING IN CIRCUIT RELATIONSHIP WITH SAID STORAGE CAPACITOR AND SAID FIRST AND SECOND TERMINALS SO AS TO EFFECTIVELY CONNECT SAID STORAGE CAPACITOR DIRECTLY ACROSS SAID FIRST AND SECOND TERMINALS WHEN AN ACTUATING SIGNAL IS APPLIED TO SAID INPUT STAGE; SAID MONOSTABLE MULTIVIBRATOR MEANS INCLUDING A HIGH IMPEDANCE DISCHARGE PATH FOR SLOWLY DISCHARGING SAID CAPACITOR AFTER DISCONNECTION OF SAID CAPACITOR FROM THE ELECTRICAL SOURCE; AND MEANS, INCLUDING ELECTROACOUSTIC TRANSDUCER MEANS AT-SUBSTANTIALLY SAID GIVEN DEPTH IN THE BOREHOLE, ELECTRICALLY COUPLED TO SAID INPUT STAGE TO SUPPLY AN ACTUATING SIGNAL TO SAID INPUT STAGE RESPONSIVE TO DETECTION OF ACOUSTIC WAVES OF PREDETERMINED MINIMUM AMPLITUDE BY SAID ELECTROACOUSTIC TRANSDUCER MEANS.