Abstract: A linear digital frequency sweep synthesizer employs an up-down counter for producing a first signal having a plurality of pulses with time interval between pulses linearly increasing with time and a phase lock loop for producing a second signal having a plurality of pulses having a frequency sweep linearized to the linearly increasing time intervals of such first signal.

Abstract: A method of identifying complex lithologies of subsurface rock formations includes the excitation of at least a portion of the rock formation with a multi-frequency electric current. The voltage resulting in the rock is measured and the phase and amplitude of such voltage is determined for each of the included frequencies. The resistivities are determined for each of the frequencies and are plotted as a function of frequency. The complex lithology of the rock formation is characterized by such plot.

Abstract: A method and system for regulating current flow through a core sample from a subterranean formation being tested for electrical impedance, including a variable-frequency current source, means for passing such current through the core sample, means for measuring such current flow, and means for regulating the current flow through the core sample so that it is dependent upon the amplitude of the current flow from the current source and is independent of non-linear variations in core inpedance responsive to the current flow through the core sample.

Abstract: An electronic power control circuit used in recording seismic data at unmanned remote locations is disclosed wherein the power requirements are minimized by segregating power distribution between continuous and non-continuous requirements.

Abstract: An electronic circuit within a control unit for use with a remotely operated seismic tape recorder is disclosed wherein recording direction and motion are detected and retained for efficient data recordation. A seismic data recording system having some portions which are continuously energized and other portions having power switched off when not in operation retains information concerning recording direction, motion and track number to provide a smooth transition between inoperation and not in operation for the other portions of the seismic data recording system.

Abstract: A gun shot control unit for a seismic exploration system compensates for the inherent delay between the shot command signal and the actual occurrence of the seismic pulse. A digital clock is synchronized with an external source. Timing pulses occurring at a time preceding the timing pulse upon which the occurrence of a seismic pulse is desired are produced by the clock. These timing pulses start a digital counter at a time preceding the desired time of occurrence of the seismic pulse. This counter is adjustable so that the delay which interposes between the timing and the actual occurrence of the seismic pulse can be minimized.

Abstract: An electronic control circuit for use with a remotely operated tape recorder wherein a rewind command is issued and executed upon energization of a power source.

Abstract: A geophone is hung from a ball bearing in a pendular fashion so that it is free to swing in any direction. Because it is weighted, it will assume the correct positioning for operation. A clamp, carried with the pendular geophone in a seismometer designed for use on the ocean floor, fixes the geophone in a rigid position when a solenoid is actuated. After the seismometer is deployed on the sea bottom, it is desired to clamp the geophone into its assumed position. The solenoid is fired upon command causing the ball to be clamped. When the seismometer is recovered the angle of inclination with respect to the vertical it assumed at the time when the geophone was clamped can be determined by measuring the angle formed by the clamped geophone and a surface known to be vertical when the seismometer rests on a flat, horizontal surface.

Abstract: In an on-bottom seismometer, the electronic system for operating the release mechanism includes a plurality of independent power sources. A plurality of release condition sensors each produce a release output upon the occurrence of a condition in which the unit is to be recovered at the water's surface. Logic circuitry responds to the release condition sensors for producing a relase signal which is applied to driving circuits for primary and secondary release devices. Switching means automatically connect the logic circuitry and the driving circuitry to an operable one of the power sources.

Abstract: A constant current source employs a correction signal which is multiplied with the output of the current source to correct for amplitude variations and thereby maintain a constant current output level.

Abstract: An ocean bottom seismometer unit records refraction waves from a seismic source. The refraction waves are digitzed and stored in a magnetic memory. Periodically, a tape recorder is started and digital samples are transferred from digital memory to tape during a time in which operation of the tape recorder will not generate spurious noise signals which interferes with the detection of the refraction waves. The water break is detected and the time of its occurrence is digitized. Only the digitized time of the water break occurrence is recorded thereby permitting shortened record length and increased record storage capacity.

Abstract: An analog reproducer unit for a seismic exploration vessel includes a discriminator for checking the repetition rate of recorded strobe pulses to discriminate valid strobe pulses from noise. The valid strobe pulses are used to store digital samples in a digital memory. These digital samples are retrieved from a magnetic record produced in an on-bottom seismometer unit.