Original oil and gas trade magazine vintage ad for SEISMOGRAPH SERVICE CORPORATION of Tulsa, OK. LORAC Purpose and Principle is to provide an accurate and convenient means of establishing position not dependent on visibility, or on the use of short range, high frequency radio waves, and determination of the position at a point P with respect to three low frequency radio transmitters. This is accomplished by phase-meters which indicate indirectly the difference in distance between the point P and two fixed land-base transmitters such as T1 and T2 and T3. This unique 1953 old petroleum oilfield seismic and drilling equipment magazine advertisement would display beautifully matted and framed.