Abstract: A tool is described for seismic data collection which may have sensors mounted along its entire length to sample both geophysical signal and noise including at least one of acoustic noise, system noise, and noise resulting from the interaction between the two. Systems and methods for acquiring borehole seismic data are also described. In contrast to conventional systems which attempt to avoid introducing noise into the collected data stream, the present systems include a sufficient type, number, and spacing of sensors to intentionally sample at least one source of noise. The methods include operating a borehole seismic acquisition system to sample both a target signal and at least one source of noise and using a processor with machine-readable instructions for separating the noise from the signal.

Abstract: In one embodiment, the present teachings provide for an efficient means to implement bidirectional data and signal channels in optical interconnects. Each optical interconnect channel may include two pairs of emitters and detectors that are imaged onto each other. Many such bidirectional optical channels may be simultaneously interconnected in dense two-dimensional arrays. The send or receive state of each bidirectional optical channel may be directly set in some embodiments by an electronic control signal. In other bidirectional optical channel embodiments, the send/receive state may be controlled locally and autonomously as derived from the output of the local detector.

Abstract: A method of determining battery performance information indicative of a performance of a battery in a device is disclosed, the method including: receiving environmental condition information indicative of environmental conditions of the device during a usage period; receiving operating parameter information indicative of one or more operating parameters of the battery during the usage period; and determining the battery performance information based at least in part on: the environmental condition information, the operating parameter information, and a performance model corresponding to the battery.

Abstract: Embodiments of the invention provide methods, systems, and apparatus for conserving power while conducting an ocean bottom seismic survey. Sensor nodes placed on an ocean floor may be configured to operate in at least an idle mode and an active mode. When a seismic source boat approached the sensor node, the node may adjust its mode of operation from an idle mode to an active mode. After the seismic source boat is no longer near the sensor node, the idle mode may be entered again to conserve power.

Abstract: An arrangement for monitoring a submarine reservoir includes a number of sensor units located in an array on the seabed, and an interrogator unit for obtaining data on the reservoir from the sensor units. The interrogator unit includes a transmitter unit for sending optical signals to the sensor array and a receiver unit for receiving modulated optical signals from the array. Optical radiation from an optical source is transmitted along an uplink optical fiber which is split in a number of positions to form the array. The receiver unit includes optical-to-electrical converters for converting the optical signals to electrical signals, a phase demodulator, a multiplexer, a signal processor, and recording unit. The interrogator unit is divided into a concentrator and an interrogator hub, where signals are transmitted between the interrogator hub and concentrator along a riser cable. This enables the interrogator to be moved between a platform and the seabed.

Abstract: A synchronous recording system is configured with a first seismograph and a second seismograph. The first seismograph includes a sensor, a GPS receiver, a data buffer, and a synchronous information transmission program that transmits synchronous information to the second seismograph, the information designating recording start time. The second seismograph includes a sensor, a GPS receiver, a data buffer, a recorder, a synchronous information reception program that receives the synchronous information, and a recording control program that starts, based on the synchronous information, recording in the recorder of oscillation data, which is recorded in the data buffer, from the designated recording start time.

Abstract: A telemetric system includes a telemetric implant, a reader unit adapted to read signals from the telemetric implant, and an antenna adapted for connection to the reader unit and to receive signals from the telemetric implant. The antenna has a first coil, a second coil, and a connector. The first coil is electrically connected to the second coil, and the connector allows for movement of the first and second coils relative to each other. The antenna may be used to send radio-frequency power to the telemetric implant and receives data from the telemetric implant.

Abstract: Systems and methods for seismic data acquisition with location aware network nodes. Based on location information of the nodes of the network, a multiplexing signature may be provided for the node. The location information may be used in conjunction with other information (e.g., location information of other nodes in the network and transmission ranges for nodes in the network) to determine collision domains. A multiplexing signature may be assigned to a node based on information regarding a collision domain to which the node belongs. As such, the assigned multiplexing signature may be used to avoid data collisions.

Abstract: To reduce a number of required channels for a survey system having seismic sensors, the seismic sensors are partitioned into groups of corresponding seismic sensors. An aggregation unit applies different transformations of signals of the seismic sensors within a particular one of the groups. The differently transformed signals within the particular group are aggregated to form an aggregated signal. The aggregated signal for the particular group is transmitted, over a channel of the survey system, to a processing system.

Abstract: The transmission system combines a self-contained, wireless seismic acquisition unit and a wireless, line-of-site, communications unit to form a plurality of individual short-range transmission networks and also a mid-range line-of-site transmission network. Each seismic unit has a power source, a short-range transceiver and a geophone disposed within a casing. Each wireless communications unit is formed of an elongated support structure on which is mounted an independent power source, mid-range radio transceiver and a short-range transceiver configured to wirelessly communicate with the short-range transceiver of the acquisition unit. Preferably, the acquisition unit is buried under the ground surface, while the wireless communications unit is positioned adjacent in the near vicinity of the buried unit and vertically protrudes above the ground.

Abstract: A method of acquiring seismic data. The method includes receiving seismic signals at one or more sensors; sampling the received seismic signals into a plurality of samples, compressing at least some of the samples in selected packets before arranging the compressed samples into packets; arranging the samples into a plurality of packets; computing packet efficiency for a packet of the plurality of packets; transmitting the plurality of packets by varying time intervals between transmissions of the packets.

Abstract: A method for the time-serial transmission of received signals of electroacoustic transducers (11), which are placed at different transducer locations (13) of a spatially spread receive arrangement (10), to a signal processing unit (12), in which at each transducer location (13) the received signals are digitized by an electronic module (20), and the digitized received signals are switched onto a data line (14, 15, 16) leading to the signal processing unit (12) in the timing pattern of a synchronization clock. To obtain a high data rate with undisturbed data transmission, the intrinsic switching-time errors of the electronic modules (20) are measured with respect to the switching times defined by the timing pattern, and compensated for at the transducer locations (13) by individual time delay of the signals to be switched.

Abstract: A method and apparatus provide an IP telephone or similar device with a mechanism to receive and at least briefly loop back discovery signals received from a telecommunications device such as an Ethernet switch while not permitting the loop back of data packet signals. No mechanical relays are required and the circuitry can be fully integrated on an integrated circuit using commonly available techniques, if desired.

Abstract: Presented are systems and methods for wireless data acquisition. The wireless data acquisition may involve synchronizing modules within a data acquisition array. The synchronized data acquisition array may be used to facilitate a seismic survey. Synchronization may be facilitated by receipt of a reference time event such that a clock is synchronized based on the reference time event.

Abstract: A seismic survey system having remote acquisition modules (RAMs) for acquiring seismic signals and communicating with a central recording system (CRU) via a network of cables, other RAMs, and line tap units (LTUs), arranged in a matrix of receiver lines and base lines. Each RAM cyclically converts analog signal values to digital, forming data packets. Interrogation commands emanating from the CRU and relayed with strategic delays by intervening LTUs and RAMs are received by the RAM. Each command causes the RAM to transmit a data packet. Strategic delays are set such that the transmission capacity of the line is best utilized. Power and frequency of transmission are selectable by the CRU to optimize performance. Cables contain multiple communication pairs. The network path between the RAM and the CRU is established from the CRU and altered in event of malfunction. All types of network elements are interconnectable. Recorded samples are synchronous.

Abstract: A method of transmitting data between a remote unit and a plurality of field service units placed over a region of interest, each field service unit acquiring seismic data from at least one seismic receiver in a plurality of seismic receivers placed in the region of interest is provided that, in one aspect, may include: specifying a data transmission time period having a fixed continuous time length for transmission of data between the remote unit and each field service unit; dividing the data transmission time period into a plurality of time slots, each time slot having a fixed time length; and transmitting data from the remote unit to each field service unit during at least one of the time slots and from each field service unit to the remote unit during at least one another time slot. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure.

Abstract: Systems and methods are provided for acquiring seismic data using a wireless network and a number of individual data acquisition modules that are configured to collect seismic data and forward data to a central recording and control system. In one implementation, a number of remote modules (301) are arranged in lines. Base station modules (302) receive information from the lines and relay the information to a central control and recording system (303). Radio links operating on multiple frequencies (F1-F12) are used by the modules (301). For improved data transfer rate, radio links from a remote module (301) leap past the nearest remote module to the next module closer to the base station.

Abstract: A system capable of operation with dynamic sockets includes a plurality of communications devices. Each of the plurality of communications devices includes high band channel radio resources capable of communications at 900-2800 MHz and socket radio resources capable of communications at 30-1000 MHz. The high band channel radio resources and the socket radio resources are significantly separated in frequency so that the high band channel radio resources and the socket radio resources are suitable for concurrent operation with no interference and minimal isolation, co-site problems to solve in each of the plurality of communications devices. The plurality of communications devices are connected to a unifying mesh network by the high band channel radio resources. The unifying mesh network is suitable for allowing the plurality of communications devices to communicate with one another.

Abstract: A survey data acquisition system acquires survey data regarding a subterranean structure. Information is wirelessly communicated between a wireless survey receiver and a wireless concentrator. The wireless communication uses a wireless protocol based on a WiFi communications technology, where the wireless protocol employs time division multiplexing in which a larger number of time slots are assigned for uplink communication from the wireless survey receiver to the wireless concentrator than for downlink communication from the wireless concentrator to the wireless survey receiver.

Abstract: To reduce a number of required channels for a survey system having seismic sensors, the seismic sensors are partitioned into groups of corresponding seismic sensors. An aggregation unit applies different transformations of signals of the seismic sensors within a particular one of the groups. The differently transformed signals within the particular group are aggregated to form an aggregated signal. The aggregated signal for the particular group is transmitted, over a channel of the survey system, to a processing system.

Abstract: A method, apparatus and system for acquiring land seismic data includes acquiring seismic data with a first autonomous seismic data acquisition unit and a second autonomous seismic data acquisition unit wherein each acquisition unit comprises a plurality of digitally controlled temperature-compensated crystal oscillators. Oscillator-based timing signals are acquired that are associated with the plurality of digitally controlled temperature-compensated crystal oscillators and a time correction is determined to apply to the seismic data acquired with the first autonomous seismic data acquisition unit. The time correction is determined using the oscillator-based timing signals from the first and second autonomous seismic data acquisition units.

Abstract: The transmission system combines a self-contained, wireless seismic acquisition unit and a wireless, line of site, communications unit to form a plurality of individual short-range transmission networks and also a mid-range, line of sight transmission network. Each seismic unit has a power source, a short-range transmitter/receiver disposed within a casing and a geophone disposed within the casing. Each wireless communications unit is formed of an elongated support structure on which is mounted an independent power source, mid-range radio transmitter/receiver; and a short-range transmitter/receiver configured to wirelessly communicate with the short-range transmitter/receiver of the acquisition unit. Preferably, when deployed, the acquisition unit is buried under the surface of the ground, while the wireless communications unit is positioned in the near vicinity of the buried unit so as to vertically protrude above the ground.

Abstract: An apparatus and method for collecting data acquired during a seismic survey are disclosed. The apparatus is a seismic survey system, comprising a plurality of data sources, a plurality of cells, and a plurality of independent pathways. The data sources are positioned about an area to be surveyed, each data source being associated with a transmitter capable of transmitting data. The cells each contain a portion of the data sources and their associated transmitters. One of the transmitters within each cell also serves as a gateway for receiving data transmitted from the other data source transmitters within the cell. The independent pathways each contain a portion of the gateways whereby data may be transmitted along each pathway via the gateways and associated transmitters in that pathway. The method is a method for conducting a seismic survey.

Abstract: In a first aspect, a method for use in a time lapse, marine seismic survey includes accessing a set of baseline seismic data; accessing a set of acquired, time lapse seismic data; and interpolating a set of time lapse seismic data from the baseline seismic data and the acquired time lapse seismic data, at least one of the baseline seismic data and the acquired time lapse seismic data being multicomponent data. In other aspects, a program storage medium is encoded with instructions that, when executed by a computing device, perform the above method and a computing apparatus programmed to perform one or more of such methods.

Abstract: A seismic data acquisition method is provided that includes receiving seismic signals at a sensor; sampling the received seismic signals into a plurality of samples, each sample having a selected number of bits (“bit length”); arranging the samples in packets, wherein some of the packets include one or more compressed samples; and transmitting the packet to a remote unit.

Abstract: A method of transmitting data between a remote unit and a plurality of field service units placed over a region of interest, each field service unit acquiring seismic data from at least one seismic receiver in a plurality of seismic receivers placed in the region of interest is provided that, in one aspect, may include: specifying a data transmission time period having a fixed continuous time length for transmission of data between the remote unit and each field service unit; dividing the data transmission time period into a plurality of time slots, each time slot having a fixed time length; and transmitting data from the remote unit to each field service unit during at least one of the time slots and from each field service unit to the remote unit during at least one another time slot. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure.

Abstract: Systems and methods are provided for acquiring seismic data using a wireless network and a number of individual data acquisition modules that are configured to collect seismic data, and forward data to a central recording and control system. In one implementation, a number of remote modules (301) are arranged in lines. Base station modules (302) receive information from the lines and relay the information to a central control and recording system (303). Radio links operating on multiple frequencies (F1-F12) are used by the modules (301). For improved data transfer rate, radio links from a remote module (301) leap past the nearest remote module to the next module closer to the base station.

Abstract: A network distributed seismic data acquisition system comprises seismic receivers connected to remote acquisition modules, receiver lines, line tap units, base lines, a central recording system and a seismic source event generation unit synchronized to a master clock. One or more high precision clocks is added to the network to correct for timing uncertainty associated with propagation of commands through the network. Seismic receivers and seismic sources are thereby synchronized with greater accuracy than otherwise possible. Timing errors that interfere with the processing of the seismic recordings are greatly reduced, thus enabling an improvement in subsurface geologic imaging.

Abstract: A seismic survey system having remote acquisition modules (RAMs) for acquiring seismic signals and communicating with a central recording system (CRU) via a network of cables, other RAMs, and line tap units (LTUs), arranged in a matrix of receiver lines and base lines. Each RAM cyclically converts analog signal values to digital, forming data packets. Interrogation commands emanating from the CRU and relayed with strategic delays by intervening LTUs and RAMs are received by the RAM. Each command causes the RAM to transmit a data packet. Strategic delays are set such that the transmission capacity of the line is best utilized. Power and frequency of transmission are selectable by the CRU to optimize performance. Cables contain multiple communication pairs. The network path between the RAM and the CRU is established from the CRU and altered in event of malfunction. All types of network elements are interconnectable. Recorded samples are synchronous.

Abstract: A seismic survey system having remote acquisition modules (RAMs) for acquiring seismic signals and communicating with a central recording system (CRU) via a network of cables, other RAMs, and line tap units (LTUs), arranged in a matrix of receiver lines and base lines. Each RAM cyclically converts analog signal values to digital, forming data packets. Interrogation commands emanating from the CRU and relayed with strategic delays by intervening LTUs and RAMs are received by the RAM. Each command causes the RAM to transmit a data packet. Strategic delays are set such that the transmission capacity of the line is best utilized. Power and frequency of transmission are selectable by the CRU to optimize performance. Cables contain multiple communication pairs. The network path between the RAM and the CRU is established from the CRU and altered in event of malfunction. All types of network elements are interconnectable. Recorded samples are synchronous.

Abstract: A system for remotely controlling, acquiring and monitoring the acquisition of seismic data. The system includes remote equipment for collecting seismic data and for transmitting and receiving communication signals to and from a remote location. The system also includes local equipment for transmitting and receiving communication signals to and from the remote location. In this manner, the collection of seismic data at remote locations can be controlled and monitored locally.

Abstract: A seismic survey system having remote acquisition modules (RAMs) for acquiring seismic signals and communicating with a central recording system (CRU) via a network of cables, other RAMs, and line tap units (LTUs), arranged in a matrix of receiver lines and base lines. Each RAM cyclically converts analog signal values to digital, forming data packets. Interrogation commands emanating from the CRU and relayed with strategic delays by intervening LTUs and RAMs are received by the RAM. Each command causes the RAM to transmit a data packet. Strategic delays are set such that the transmission capacity of the line is best utilized. Power and frequency of transmission are selectable by the CRU to optimize performance. Cables contain multiple communication pairs. The network path between the RAM and the CRU is established from the CRU and altered in event of malfunction. All types of network elements are interconnectable. Recorded samples are synchronous.

Abstract: A system is disclosed for synchronizing a clock in a well containing a drill string with a clock located near the surface of the well. The system includes devices for transmitting and receiving a pair of acoustic signals between locations associated with each clock and processing those signals. The system determines the time of arrival of each acoustic signal by analyzing the shape of a function of the acoustic signal chosen from a group of functions suitable to determine a clock offset with millisecond accuracy.

Abstract: A data acquisition system has a central station connected to a plurality of nodes over a network. Each node is connected to receive signals from one or more sensors ad each is configured to have substantially the same transmission delay to said central station. The central station is configured to notify all nodes of an event time at which a data event, such as a seismic shot, occurred.

Abstract: A seismic data acquisition system is featured that utilizes a series of nearly identical seismic shots (SISS) to synchronize and to communicate with novel data acquisition units (NDAU) located in the field. Each SISS seismic shot is carefully timed to provide synchronization to each NDAU, and to allow the NDAU to correct for the time drift of its internal clock. Further, each NDAU is programmed with a number of menus, which are used to interpret the seismic shots received from a seismic source. Thus, communication from a central or headquarter site to each NDAU is facilitated, allowing for a change in production schedule and other variables. In addition, the disclosed seismic data acquisition system features movable SISS source sites and overlapping production and SISS shots.

Abstract: A system and method for synchronizing collection of seismic data used for seismic surveys. In one embodiment, positioning signals received from a positioning system, such as the Global Positioning System, are used to acquire a highly accurate time value. Data collection is then initiated at a prespecified time using the time determined from the positioning signal.

Abstract: Disclosed is a telemetry data transmission circuit for a towed hydrophone streamer, the streamer comprised of a plurality of series-coupled modules. The transmission circuit comprises: (1) a slave clock input in a first module capable of receiving a master timing signal from a master clock source located in a second module, the master timing signal capable of synchronizing an operation of the transmission circuit to allow the transmission circuit to place local telemetry data on a data bus coupled to the transmission circuit and running a length of the streamer, (2) a local clock input in the first module capable of receiving a local timing signal from a local clock source located in the first module, the local timing signal alternatively capable of synchronizing the operation of the transmission circuit and (3) a clock source selection circuit capable of allowing the local clock source to synchronize the operation of the transmission circuit as a function of a condition of the master timing signal.

Abstract: A data collection and transmission system for gathering high count vertical seismic data is disclosed using a sequence of vertically aligned seismic receivers, the analog outputs from which are sequentially analog sampled and time multiplexed onto a common pair of data conductors in the support and transmission cable. The data is time demultiplexed at the surface and appears substantially as digital data because of the relatively short sampling times. Such data is converted into analog data with conventional digital-to-analog converter means.A clock signal activates counters for establishing non-overlapping data gates in the respective sondes, the operation of the gates supplying the cable with the respective receiver analog signals in a sequence from bottom to top, simultaneously switching off previously gated signals until a clock reset pulse resets the entire sonde string.

Abstract: Modular device for the reception, the acquisition and the transmission, to a central control and recording unit, of signals picked up by a very large number of seismic acoustic receivers distributed along a streamer of great length under water in operation.The receivers in each one of the sections (Tk) of the streamer are arranged in several groups and the receivers (H1 to Hp) of a same group are connected with an acquisition unit (U1 to Um) located close to them. All the units of each section are connected through digitized command and data transmission lines (LOC,BD) with a common memory and a transmission management unit in an interconnection box (Bk) at one end of the streamer section. Transferring a great part of the electronic equipment into the streamer sections is very favorable for the balancing of the streamer in the water, for obtaining a good signal to noise ratio and it facilitates the development and the exploitation of the material.

Abstract: Method and device for the high-rate transmission of data between a multiplicity of acquisition apparatuses (Ai) and a central station to which they are connected by a common transmission channel (V1) for commands and by a high-rate transmission channel (V2) for data.A first clock signal (H1) serves for the transmission of the orders, the acquisition of the data and their storage in a memory (10). A second clock signal (H2) with a higher frequency non synchronous with the first one is used for reading the data stored by each acquisition apparatus. A determined time interval (or window) is assigned to each apparatus and the reading of each stored sample is activated by an order signal indicating the beginning of this window.Application to a seismic transmission system for example.

Abstract: A method and apparatus for acquiring acoustical data from a borehole and is especially useful in carrying out tomogrphy surveys. The borehole digital geophone (BDG) tool of the present invention is capable of operating from a standard, 7-conductor logging cable with no special cables being required since the individual digital geophone modules (DGM) which form the BDG tool are connected together by short, separate lengths of the same 7-conductor cable. Each DGM acquires, digitizes, stacks, and stores data generated by its own three-component geophone assembly prior to transmitting these signals to the surface over a dedicated conductor in the cable thereby substantially increasing the sample rate of the tool which, in turn, substantially reduces the field time to run a tomography survey.

Abstract: In a marine seismic data acquisition system, a plurality of seismic data transmission paths are utilized to conduct seismic data to a central recording unit from seismic data acquisition modules positioned along the length of cable. Signals from a plurality of data acquisition modules are applied to each of the transmission paths. Data acquisition modules which apply seismic signals to a given transmission path may be spaced and substantially uniform distances along the length of the cable and may be interspersed with data acquisition modules which apply seismic data to each of the other transmission paths. The operation of the data acquisition modules is synchronized by means of a signal transmitted continually from a central recording unit. Each section of the cable includes a plurality of remote units distributed along the cable section for detecting seismic signal.

Abstract: An acousto-optical seismic sensor array includes a distributed set of optical-fiber sensing coils. A light pulse is launched through the sensing coils in serial order. The light pulse is cumulatively data-modulated by the respective sensing coils and is returned as a time-division multiplexed pulse train. The pulse train is split into a first pulse train and a retarded second pulse train. The retardation time equals the travel-time delay of a light pulse between sensors. The retarded pulse train is compared with the first pulse train to determine the phase shift therebetween for consecutive pulses. The phase shift is an analog of the quantity being sensed.

Abstract: A digital marine seismic system employes a plurality of data acquisition control modules which simultaneously digitize analog seismic signals. The control modules also are selectably addressable in that each module is uniquely programmed to respond only to a particular control word. The system allows a large number of channels, such as 480 channels, on a simple transmission system, such as a twisted pair of wires. Each module includes a power switch to sequentially apply power to downstream modules. Selective addressing of the switches allow testing of specific modules for power malfunctions.

Abstract: For use in an acoustic logging tool, an apparatus which digitizes simultaneously obtained acoustic signals is set forth in the preferred and illustrated embodiment. The device cooperates with N acoustic receivers in a sonde. After an acoustic pulse is transmitted, data is observed at all N acoustic receivers. This apparatus comprises a multiplexer which is connected to the several receivers. The several input signals are multiplexed, thereafter input to a digital data converter forming a procession of output digital words, and the words are stored in a selected order in a digital data buffer. They are delivered to the surface through a telemetry transmitter at a slower rate than the rate at which the data is created. In addition, a transmitter monitor is included. This provides a signal alternately digitized for a specified interval to enable coordination of the data reduction from the acoustic receivers in contrast with the timing of the transmitted acoustic pulse.

Abstract: A two stage, decentralized device for transmitting seismic data information from seismic receivers of a seismic streamer to a central recorder on a ship, including a series of interconnected sections each having a plurality of seismic receivers distributed over it's length, seismic signal acquisition apparatus for digitizing and storing seismic signals coming from a group of seismic receivers to which a respective seismic signal acquisition apparatus is connected, central control and recording device on the ship and assembly of electronic modules each disposed in the vicinity of a seismic receiver and being capable of amplifying and filtering the seismic receiver signals.

Abstract: For use in an acoustic logging tool, an apparatus which digitizes simultaneously obtained acoustic signals is set forth in the preferred and illustrated embodiment. The device cooperates with N acoustic receivers in a sonde. After an acoustic pulse is transmitted, data is observed at all N acoustic receivers. This apparatus comprises a multiplexer which is connected to the several receivers. The several input signals are multiplexed, thereafter input to a digital data converter forming a procession of output digital words, and the words are stored in a selected order in a digital data buffer. They are delivered to the surface through a telemetry transmitter at a slower rate than the rate at which the data is created. In addition, a transmitter monitor is included. This provides a signal alternately digitized for a specified interval to enable coordination of the data reduction from the acoustic receivers in contrast with the timing of the transmitted acoustic pulse.

Abstract: A real time seismic telemetry system includes a central station (10) for communication with a plurality of remote data acquistion units (14). The command station (10) has a command unit (34) for controlling the operation of a transmitter (40) for providing instructions to the data acquistion units (14). The data acquistion units (14) receive the data on a receiver (80) and process the data in a logic control circuit (88). Remote data is picked up with a hydrophone (30) and converted to digital data for transmission through a transmitter (78) which is tuned to a discrete channel for each data acquistion unit (14). The command station (10) has a PCM receiver (62) tuned to each of the channels for demodulating the data stream therefrom. A digital receiver (66) is provided for synchronizing and processing the data. The digital receiver (66) synchronizes both to the bit rate and to the beginning and ending of the digital word such that data contained in the digital word can be multiplexed onto a data bus (68).

Abstract: In a two-stage, time-division multiplexing method and apparatus, a plurality of sensors are disposed at equal intervals along a plurality of transmission channels. An interrogation signal is transmitted from a recording station to all of the sensors along each channel. Because of the spatial arrangement of each sensor along the telemetric system and different propagation path lengths along each channel, the output signals from the sensors are time-division multiplexed along each channel. The multiplexed signals along each channel are time-division multiplexed a second time upon arrival at the recording station where the signals from each channel are interleaved with each other.

Abstract: Transmitting information from a central receiver and recorder utilizes plural series-connected transmission modules, each connected to a respective data acquisition unit. The transmission modules are sequentially connected along plural transmission lines, at least two of which are outgoing data transmission lines for transmitting information from the central receiver and recorder to the acquisition units. At least two other lines are incoming data transmission units to the central receiver and recorder. Each transmission module has, for each outgoing line, respective line receivers, informaiton decoders, line transmitters and matrices of transmission line selectors controlled by individual information decoders, and a selector unit which ensures that a signal from a selected outgoing transmission line is transmitted to the next module on all outgoing transmission lines.