Continuous wave apparatus with delay gated filter

Claim 1

A GEOPHYSICAL CONTINUOUS WAVE ANALYZING SYSTEM FOR DETERMINING THE TRAVEL TIME OF A SEISMIC SIGNAL OF CYCLICALLY VARYING FREQUENCY RECEIVED AT A POINT REMOTE FROM THE POINT OF GENERATION OF SAID SIGNAL AND RECORDED ON A RECORD MEDIUM BY COMPARING SAID SEISMIC SIGNAL WITH A SECOND SIGNAL OF CYCLICALLY VARYING FREQUENCY HAVING THE SAME FREQUENCY VARIATIONS AS SAID SEISMIC SIGNAL AND RECORDED IN SIDE-BY-SIDE RELATIONSHIP WITH SAID SEISMIC SIGNAL ON SAID RECORD MEDIUM, COMPRISING: (A) MEANS FOR ROTATION OF THE RECORD MEDIUM, (B) A FIRST DETECTOR MOUNTED ADJACENT SAID RECORD MEDIUM AND ADAPTED TO DETECT SAID SEISMIC SIGNAL AND CONVERT IT TO A FIRST ELECTRICAL SIGNAL, (C) A SECOND DETECTOR MOUNTED ADJACENT SAID RECORD MEDIUM AND ADAPTED TO DETECT SAID SECOND SIGNAL AND CONVERT SAID SECOND SIGNAL TO AN ELECTRICAL SIGNAL, (D) A VARIABLE DELAY MEANS CONNECTED TO THE OUTPUT OF SAID SECOND DETECTOR, (E) A FILTERING UNIT CONNECTED TO THE OUTPUT OF SAID FIRST DETECTOR AND THE OUTPUT OF SAID DELAY MEANS WHEREBY THE PASS BAND OF SAID FILTERING UNIT IS CONTROLLED BY THE OUTPUT FROM SAID DELAY MEANS AND SAID FIRST SIGNAL IS PASSED THROUGH SAID FILTERING UNIT WHEN SAID FIRST SIGNAL AND THE DELAYED SECOND SIGNAL ARE IN TIME PHASE WITH ONE ANOTHER, AND (F) RECORDING MEANS CONNECTED TO THE OUTPUT OF SAID FILTERING UNIT AND ADAPTED TO RECORD THE OUTPUT OF SAID FILTERING UNIT.