Combination logging system

Claim 1

IN A LOGGING SYSTEM FOR MAKING SUBSURFACE MEASUREMENTS OF A PLURALITY OF SUBSURFACE CONDITIONS, THE IMPROVEMENT COMPRISING: A LOGGING TOOL ADAPTED TO BE MOVED THROUGH A BOREHOLE; A SHEATHED SUPPORTING CABLE CONNECTED TO SAID TOOL, SAID CABLE CONTAINING A SINGLE INSULATED CONDUCTOR; FIRST LOGGING MEANS POSITIONED IN SAID TOOL FOR OBTAINING AND TRANSMITTING THROUGH SAID CONDUCTOR A FIRST LOGGING SIGNAL AS A PULSATING DIRECT CURRENT SIGNAL MADE UP OF A SERIES OF PULSES OF ONE POLARITY WITH THE AMPLITUDE OF SAID PULSES PROVIDING SIGNIFICANT INFORMATION; SECOND LOGGING MEANS POSITIONED IN SAID TOOL FOR OBTAINING AND TRANSMITTING THROUGH SAID CONDUCTOR A SECOND LOGGING SIGNAL AS A SERIES OF PULSATING DIRECT CURRENT SIGNALS MADE UP OF A SERIES OF PULSES OF THE OPPOSITE POLARITY, WITH THE FREQUENCY OF OCCURRENCE OF THE PULSES OF SAID SECOND SIGNAL BEING SUBSTANTIALLY GREATER THAN THE FREQUENCY OF PULSES OF SAID FIRST SIGNAL AND WITH SUCH FREQUENCY OF OCCURRENCE OF PULSES OF SAID SECOND SIGNAL PROVIDING SIGNIFICANT INFORMATION; FIRST RECEIVING MEANS FOR MAKING A MEASURE OF THE PULSE AMPLITUDE OF SAID FIRST SIGNAL; SECOND RECEIVING MEANS FOR MAKING A MEASURE OF THE PULSE RATE OF SAID SECOND SIGNAL; FIRST GATING MEANS CONNECTED BETWEEN SAID CONDUCTOR AND SECOND LOGGING MEANS FOR INTERRUPTING SAID SECOND LOGGING SIGNAL; MEANS RESPONSIVE TO SAID FIRST LOGGING MEANS FOR ACTUATING SAID FIRST GATING MEANS DURING TRANSMISSION OF SAID FIRST LOGGING SIGNAL ON SAID CONDUCTOR.