Abstract: A seismic data acquisition unit includes a housing, and disposed within the housing, communication circuitry, and circuitry configured to detect and digitize seismic signals. The communication circuitry includes a first transmitter plate, a second transmitter plate, a first receiver plate, a second receiver plate, and a driver. The first and second transmitter plates, and first and second receiver plates, are adjacent a wall of the housing. The driver is coupled to the first transmitter plate and the second transmitter plate. The receiver is coupled to the first receiver plate and the second receiver plate. The communication circuitry transmits digitized seismic signals via a first capacitor that includes the first transmitter plate, and a second capacitor that includes the second transmitter plate. The communication circuitry receives information via a third capacitor that includes the first receiver plate, and a fourth capacitor that includes the second receiver plate.

Abstract: A seismic data acquisition unit includes a housing, and disposed within the housing, communication circuitry, and circuitry configured to detect and digitize seismic signals. The communication circuitry includes a first transmitter plate, a second transmitter plate, a first receiver plate, a second receiver plate, and a driver. The first and second transmitter plates, and first and second receiver plates, are adjacent a wall of the housing. The driver is coupled to the first transmitter plate and the second transmitter plate. The receiver is coupled to the first receiver plate and the second receiver plate. The communication circuitry transmits digitized seismic signals via a first capacitor that includes the first transmitter plate, and a second capacitor that includes the second transmitter plate. The communication circuitry receives information via a third capacitor that includes the first receiver plate, and a fourth capacitor that includes the second receiver plate.

Abstract: A seismic data acquisition unit includes circuitry to detect and digitize a seismic signal, and timing circuitry to control a time of acquisition of each sample of the seismic signal. The timing circuitry include a voltage controlled oscillator (VCO), a local clock incremented by the VCO, and a reference time receiver. The timing circuitry powers on the reference time receiver to generate a reference time value based on signals received from a reference time source, and measures time deviation of the local clock from the reference time value. The timing circuitry determines an adjustment value to apply to the VCO over a time interval during which the reference time receiver is not powered on. The adjustment value is selected to gradually bring the local clock into synchronization with the reference time source over the time interval at a time that the reference time receiver is to be next powered on.

Abstract: A seismic data acquisition unit includes circuitry to detect and digitize a seismic signal, and timing circuitry to control a time of acquisition of each sample of the seismic signal. The timing circuitry include a voltage controlled oscillator (VCO), a local clock incremented by the VCO, and a reference time receiver. The timing circuitry powers on the reference time receiver to generate a reference time value based on signals received from a reference time source, and measures time deviation of the local clock from the reference time value. The timing circuitry determines an adjustment value to apply to the VCO over a time interval during which the reference time receiver is not powered on. The adjustment value is selected to gradually bring the local clock into synchronization with the reference time source over the time interval at a time that the reference time receiver is to be next powered on.

Abstract: A system for seismic data acquisition includes data recorders that lack external electrical connectors. A seismic data recorder includes a housing. Within the housing the seismic data recorder includes circuitry configured to detect and digitize seismic signals and communication circuitry. The communication circuitry includes a first transmitter plate adjacent a wall of the housing, and a first driver coupled to the first transmitter plate. The communication circuitry configured to communicate the digitized seismic signals to a data retrieval unit that is external to the data acquisition unit via a capacitor formed by the first transmitter plate, the wall of the housing, and a receiver plate external to the housing.

Abstract: A system for seismic data acquisition includes data recorders that lack external electrical connectors. A seismic data recorder includes a housing. Within the housing the seismic data recorder includes circuitry configured to detect and digitize seismic signals and communication circuitry. The communication circuitry includes a first transmitter plate adjacent a wall of the housing, and a first driver coupled to the first transmitter plate. The communication circuitry configured to communicate the digitized seismic signals to a data retrieval unit that is external to the data acquisition unit via a capacitor formed by the first transmitter plate, the wall of the housing, and a receiver plate external to the housing.

Abstract: A method for wrapping continuous strands of steel wire about a seismic cable including interconnected sensor sections and conductor sections where a cross sectional diameter of the sensor section is at least four times that of the conductor section. Two layers of armoring are provided with a first layer wrapped in a first angular direction opposite that of the second layer. A stranding assembly is provided which has two selective positions, one for providing a die hole for stranding the conductor section, another for providing a passage hole for allowing the sensor section to pass after wrapping with armor wire.

Abstract: A buoyant marine fender element is disclosed, with guides for securing it to a mooring facility such as a piling, which allows the fender element to rise and fall with the tide or waves. The fender element is cylindrical in form and sealed at each end by an enlarged end cap, which serves as a stop element for limiting up and down movement upon contacting a guide element.