Abstract: In one aspect, the present invention reduces electromagnetic interference (EMI) caused by a capacitive dropper power supply by synchronizing the openings and closings of a shunt switched used for regulation control of the DC output voltage generated by the power supply, to zero crossings of AC current from the current-limiting resistor disposed in series at the AC input of the power supply. In one or more other embodiments, the capacitive dropper power supply includes disconnect circuitry that senses a loss of the input AC voltage source and in response wholly or partly disconnects internal regulation control circuitry from the supply's output filter capacitor to reduce the current drawn from the filter capacitor, thereby reducing the decay rate of the DC output voltage from the filter capacitor. The contemplated power supply may also be implemented in a Bipolar, BiCMOS or CMOS process, for realization in a compact integrated circuit device.

Abstract: In one aspect, the present invention reduces electromagnetic interference (EMI) caused by a capacitive dropper power supply by synchronizing the openings and closings of a shunt switched used for regulation control of the DC output voltage generated by the power supply, to zero crossings of AC current from the current-limiting resistor disposed in series at the AC input of the power supply. In one or more other embodiments, the capacitive dropper power supply includes disconnect circuitry that senses a loss of the input AC voltage source and in response wholly or partly disconnects internal regulation control circuitry from the supply's output filter capacitor to reduce the current drawn from the filter capacitor, thereby reducing the decay rate of the DC output voltage from the filter capacitor. The contemplated power supply may also be implemented in a Bipolar, BiCMOS or CMOS process, for realization in a compact integrated circuit device.

Abstract: An asset locator device including (a) a wireless receiver capable of receiving an identifier signal transmitted from a short range wireless transmitter device; (b) a wireless transmitter capable of transmitting a message to a space based network; (c) a positioning system capable of determining the location of the locator device; (d) a vibration sensor; and (e) a controller. The controller instructs the asset locator to: (i) attempt to detect the identifier signal from the transmitter device if the vibration sensor senses vibration; and (ii) transmit a signal, including an asset location, to the space based network if: (1) the identifier signal is not detected; and (2) location fixes from the positioning system indicate a location change of the asset.

Abstract: An asset locator device including (a) a wireless receiver capable of receiving an identifier signal transmitted from a short range wireless transmitter device; (b) a wireless transmitter capable of transmitting a message to a space based network; (c) a positioning system capable of determining the location of the locator device; (d) a vibration sensor; and (e) a controller. The controller instructs the asset locator to: (i) attempt to detect the identifier signal from the transmitter device if the vibration sensor senses vibration; and (ii) transmit a signal, including an asset location, to the space based network if: (1) the identifier signal is not detected; and (2) location fixes from the positioning system indicate a location change of the asset.

Abstract: A cellular wireless packet data communication system containing transmit-only endpoint devices which transmit to receive-only base stations. The system is configured to allow for large area coverage (e.g., a metropolitan area) with far fewer number base stations than are required with conventional two-way cellular systems. The base station coverage areas are configured to overlap, allowing for reception of packets at multiple base stations. A data concentrator resolves redundantly received messages. The network is configurable as a WAN, a LAN, or a combination of the two. Novel modulation techniques (e.g., a 16QAM submodulation together with a 7FSK modulation) are used such that low cost components can be used in the transmitters and receivers while achieving outstanding probability of success performance. The endpoint devices are battery operated and accordingly, are designed for low power consumption and multi-year battery life.

Abstract: A GPS-based underwater cable positioning system for use in determining the shape and position of hydrophone streamers towed underwater behind survey vessels involved in marine seismic prospecting. The system includes a plurality of surface units towed behind the vessel. Each surface unit includes a GPS receiver to receive radio frequency GPS signals and to determine its positions. Each surface unit also has an acoustic transmitter to transmit an acoustic message signal representing its position and an optional time stamp into the water. Acoustic receiver units, attached spaced apart locations along one or more streamer cables, each include an acoustic receiver to receive the acoustic message signals from the surface units and to determine its position from the message signals. To augment the message signals from the surface units at locations distant from the surface units, acoustic transceiver units may be used.