Abstract: A cable-entry seal for a multicontact seismic cable connector consists of a cable anchor molded near an end of a multiconductor cable and a sphincter grommet. A compression sleeve, urged by a gland nut axially compresses the sphincter causing it to expand radially to form a water tight seal. A rotatable locking cam has a spiral slot lined with a low friction material to lock a pair of cable connectors together.

Abstract: An optical telemetric system for use in seismic exploration consists generally of a recorder, a plurality of transceivers, and a like number of cable sections interconnecting each transceiver in parallel with others and the recording unit. A fiber optic transmission channel is provided within each cable section and is interconnected by an optic-fiber delay loop within each transceiver, thus providing a contiguous, optically-continuous data and control channel. Within each transceiver, a logic circuit and associated data acquisition unit is optically coupled to the data and control channel so as to bidirectionally receive signals from, and transmit signals to the recorder. The logic circuit of each transceiver also is able to measure the strength of a received signal propagating in the data and control channel, and if necessary, augments the signal in the original propagation direction.

Abstract: A dual-mode vibrator for alternately injecting P-waves and S-waves in the earth including a hydraulically driven shaker assembly, a ground-contacting base plate, and a jacking means for raising and lowering the base plate relative to a vehicle. The shaker assembly is supported above, and coupled to the base plate by a supporting means. The supporting means has a first configuration for coupling the shaker assembly to the base plate for generating P-waves and a second configuration for pivotally coupling the shaker assembly to the base plate and to a rigid member associated with the vehicle for injecting S-waves.

Abstract: An apparatus for preventing thermally-induced stress fatigue in a vibrator support housing consists of a stress compensator that absorbs thermal dimensional changes between major structural components made of dissimilar materials. The stress compensator consists of a hydraulic clamp wedged between the free end of a vibrator actuator piston shaft and the supporting housing. Actuated by the substantially-constant system hydraulic pressure, the hydraulic clamp maintains a substantially constant clamping force between the actuator piston shaft and the supporting housing. Thermally-induced stresses are absorbed by the hydraulic system.

Abstract: The compound accelerometer is made by combining two simple accelerometer units. The simple accelerometer units consist of a hollow container closed at each end by a piezo-electric transducer. The two transducers are oppositely polarized and are selected to have a desired combined series capacitance value. The container is partially filled with a volume of heavy liquid and the accelerometer is excited. During excitation, the output voltage is continuously measured and the volume of liquid is microadjusted until the output voltage equals a prescribed level. The outputs of the individual transducers are measured, the residual voltage difference is tabulated and the dominant transducer is identified. Two simple accelerometer units having the same residual voltage difference are secured together with the dominant transducers facing oppositely with respect to each other.

Abstract: A method for manufacturing a compound accelerometer that is maximally sensitive to a desired acceleration vector to the exclusion of orthogonal vectors. The compound accelerometer is made by combining two simple accelerometer units. The simple accelerometer units consist of a hollow container closed at each end by a piezo-electric transducer. The two transducers are oppositely polarized and are selected to have a desired combined series capacitance value. The container is partially filled with a volume of heavy liquid and the accelerometer is excited. During excitation, the output voltage is continuously measured and the volume of liquid is microadjusted until the output voltage equals a prescribed level. The outputs of the individual transducers are measured, the residual voltage difference is tabulated and the dominant transducer is identified.

Abstract: An air gun of the reciprocating shuttle type includes a split-ring sleeve valve that is expandable against the inner wall of a firing chamber. The sleeve valve encircles the shuttle body. The shuttle body and the sleeve valve include a set of air release orifices that are alignable with a corresponding set of air exhaust ports of the firing chamber.

Abstract: A cross country vehicle for seismic exploration is provided wherein a first drive means, such as wheels can be conveniently interchanged, in the field, for a second drive means having a different configuration such as endless tracks. The interchange is enabled by use of a pre-existing lifting means associated with a seismic acoustic source.

Abstract: A data processing system having an architecture that will allow high-speed direct device-to-device data transfers without the necessity of first detouring the data through a computer memory. The system consists of a host computer and a remote signal processing subsystem connected thereto. A Direct Device Access Bus and a plurality of data processing devices are provided. A controller associated with a Signal Processing Subsystem supervisor, selectively interconnects desired ones of a set of data processing devices via the Direct Device Access Bus to provide direct communication between the selected devices within a set. Several sets of devices can be serviced concurrently by the technique of dynamic time slot allocation.

Abstract: A geophone marsh case, for use in wetlands, contains a geophone. An electric cable delivers geophone signals to the outside world and provides a means for pulling an emplaced geophone from the mud. The cable is anchored to the marsh case both internally and externally in order to preserve the integrity of a water seal that surrounds the cable in the cable entry port of the marsh case.

Abstract: A power stage servo valve for a seismic vibrator includes a stationary orifice plate defining a plurality of valve ports having a first shape. A rotary orifice plate, abutting the stationary orifice plate, defines a like plurality of valve ports that have a shape different from the valve ports in the stationary orifice plate. The configuration and shape of the rotary valve ports is such that the valve opens more quickly than it shuts off when the plate is rotating continuously in one direction at a desired angular velocity.

Abstract: A robust air gun fire time sensor consists of a housing to which is secured a protruding nonmagnetic internal barrel having a bore. The bore is closed at one end by a magnetic end cap defining an air chamber and the bore is in fluid communication with the firing chamber of an air gun. A generator coil surrounds the barrel. A bar magnet is floatingly mounted inside the bore and is urged against a shoulder formed in the end cap. When the air gun is charged with compressed air, some of the air becomes entrapped in the air chamber. When the air gun is fired, the entrapped compressed air in the air chamber pushes the bar magnet away from the shoulder. The collapsing magnetic field creates a transient electric pulse in the generator coil.

Abstract: A data processing system having an architecture that will allow high-speed direct device-to-device data transfers without the necessity of first detouring the data through a computer memory. The system consists of a host computer and a remote signal processing subsystem connected thereto. A Direct Device Access Bus and a plurality of data processing devices are provided. A controller associated with a Signal Processing Subsystem supervisor, selectively interconnects desired ones of a set of data processing devices via the Direct Device Access Bus to provide direct communication between the selected devices within a set. Several sets of devices can be serviced concurrently by the technique of dynamic time slot allocation.

Abstract: A data telemetric system consists of a pair of optical fibers, each having an associated electrically conductive member. One of the fibers is a reference fiber and the other fiber constitutes a data transmission fiber. A light beam, from a source such as a laser, is launched from one end into both fibers. A signal transfer sensor is non-invasively coupled to the data fiber and applies forces to that fiber that are related to data signals thereby to modulate the light beam therein. A comparator at the other end of the pair of fibers compares variations in a characteristic of the modulated beam with corresponding characteristics of the reference beam to decipher the transmitted information. Means are provided in the signal transfer sensor for inductively sensing control and power signals transmitted through the electrically conductive member.

Abstract: A geophone testing apparatus includes a plurality of force detectors upon each of which is mounted a corresponding geophone. An electrical step function is applied to the active elements of the geophones to generate mechanical output transients. The mechanical output transients are detected by the force detectors which generate corresponding electrical signals. The signals are analyzed to determine the sensitivity, damping and natural frequency of each of the geophones under test. A multiplexer is provided so that all of the geophones may be tested at the same time.

Abstract: The electronic roll-along switch consists of several input multiplexers, each having a number of inputs that are connected to seismic detectors, and an output line. A plurality of multiple-input sample-and-hold modules are provided. Corresponding inputs of the respective sample-and-hold modules are paralleled. The output lines of the input multiplexers are connected in consecutive order to the paralleled input of the sample-and-hold modules. The output of each sample-and-hold module is connected to an output amplifier which is couplable to a multichannel seismic recording system. A master controller provides circuitry for connecting any set of several seismic detectors to a like number of channels in the seismic recording system.

Abstract: A decentralized seismic data recording system includes a central station and a plurality of remote seismic recording units that are incommunicado with the central station during a normal recording operation. A master clock is provided in the central station. A local clock is provided in each remote recording unit. At the beginning of a work period, the local clocks are synchronized with the master clock. Thereafter, a plurality of seismic data recordings are made. At the end of a work period, the time difference due to tuning drift between the master clock and each respective local clock is ascertained and is recorded. The time difference is linearly prorated over the recordings made during the work period, thereby synchronizing the time base of each seismic data recording with the master clock. Provision is made to validate each seismic data recording to prevent accidental recording of false data in event of a misfire or a non-fire of the seismic source.

Abstract: A spring-suspended, moving-coil transducer to be tuned is mounted on a dynamic test fixture and excited by an oscillatory driving force calculated to drive the transducer at a desired resonant frequency. A laser beam, sensitive to a difference between the actual resonant frequency of the transducer and the desired resonant frequency, is focused on the spring. The energy of the laser beam alters the elastic constant of the spring by trimming or etching material therefrom until the difference between the actual resonant frequency of the transducer and the desired resonant frequency is eliminated.