Abstract: Embodiments of the present invention relate to a method and apparatus for reducing interference in a positioning system. According to one or more embodiments of the present invention, the receiver in a conventional positioning system is configured to communicate with a terrestrial broadcast station. The terrestrial broadcast station transmits assistance signals to the receiver and may be another receiver. The assistance signals enable the receiver to locate very weak signals being transmitted from the satellites in the positioning system. In one embodiment, the assistance signals include Doppler frequencies for the satellites. In another embodiment, the assistance signals include Ephemeris data. In another embodiment, the assistance signals include almanac data. In other embodiments of the present invention, the assistance signal includes navigation bits demodulated from the carrier phase inversion signal of the satellite, time synchronization signals, and pseudo range differential corrections.

Abstract: Embodiments of the present invention relate to a method and apparatus for reducing interference in a positioning system. According to one or more embodiments of the present invention, the receiver in a conventional positioning system is configured to communicate with a terrestrial broadcast station. The terrestrial broadcast station transmits assistance signals to the receiver and may be another receiver. The assistance signals enable the receiver to locate very weak signals being transmitted from the satellites in the positioning system. In one embodiment, the assistance signals include Doppler frequencies for the satellites. In another embodiment, the assistance signals include Ephemeris data. In another embodiment, the assistance signals include almanac data. In other embodiments of the present invention, the assistance signal includes navigation bits demodulated from the carrier phase inversion signal of the satellite, time synchronization signals, and pseudo range differential corrections.

Abstract: A telephone subscriber testing system is disclosed in which all tests may be performed from a central office. A central office test device is connected to the central office by a separate telephone line with a telephone number of its own. Moreover, a dedicated command channel connects the office test device with a remote test device over the carrier lines. This dedicated channel is used to communicate commands and transmit test results back to the central office. By causing the remote device to "dial up" the office device, the entire trunk loop through the PCM trunk and the central office switching equipment can be tested directly in one measurement at the central office.

Abstract: In an all-digital telephone system for communication between a central office and widely scattered subscriber locations, means are disclosed for carrying digital service from the central office to various distribution locations over T1-type equipment and from the distribution locations to subscriber locations over ordinary two-wire lines using time-shared bidirectional pulse code modulation.A salient feature of the system is the provision of "smart repeater" means which permit unidirectional or bidirectional access between any digital subscriber line and any channel of the T1 line under the control of the central office. Provisions are also made in the system for the transmission of slow-speed signals suitable for the remote reading information from sensing devices at the subscriber locations and for the remote operation of suitable devices at the subscriber locations.

Abstract: Simple and reliable decoding of T-1 type pulse code information is achieved by combining a fast-acting recirculating frame recovery circuit with a simplified signal output register. The frame recovery circuit uses a recirculating 386-bit control word in which all positions which cannot be the main-frame bit position are continuously recorded by the continuous comparison of pairs of incoming data bits spaced 386 bits apart. Following a sufficient number of iterations of the control word to statistically identify all 385 non-main-frame bit positions with a high degree of probability, the remaining unidentified position is read out as the main-frame bit position, and is used to reset the frame clock generator.

Abstract: Conventional PCM encoders are made capable of handling a much larger number of telephone channels than normally possible by varying the set-up interval of the encoder in accordance with the maximum signal level to be set up.

Abstract: An essentially non-dissipative, strap-free, continuously adjustable power unit inherently impervious to shorts and open circuits for powering repeaters in a T1 or similar telephone span line is disclosed. The unit uses a pulse-width modulated inverter in the converter input circuit to produce a variable-voltage D.C. output to the span line. The pulse width or duty cycle of the inverter is controlled by a control logic which senses the span line current and maintains it at a selectable predetermined level without any apreciable power dissipation.

Abstract: An automatic span line switch for PCM communication lines is disclosed which isolates alarm conditions to an actual span line failure, as distinguished from failures in the terminal equipment. In addition, the switch uses a specific code transmission to provide fast switching and to permit identification of the direction of failure. Although the circuit is capable of switching span segments individually and independently, it can transmit an alarm to a distant central office and automatically establish an appropriate test loop in the presence of test transmissions when needed to permit single-end troubleshooting. The switch further tests the dead line continuously and stringently for error-free data transmission, and automatically resets without disturbing traffic when the trouble has been corrected. An extremely flexible priority system for selected channels is also provided, and the circuitry on both ends of all channels (including the protective channel) is identical to minimize parts inventory costs.

Abstract: An automatic span line switch for PCM communication lines is disclosed which isolates alarm conditions to an actual span line failure, as distinguished from failures in the terminal equipment. In addition, the switch uses a specific code transmission to provide fast switching and to permit identification of the direction of failure. Although the circuit is capable of switching span segments individually and independently, it can transmit an alarm to a distant central office and automatically establish an appropriate test loop in the presence of test transmissions when needed to permit single-end troubleshooting. The switch further tests the dead line continuously and stringently for error-free data transmission, and automatically resets without disturbing traffic when the trouble has been corrected. An extremely flexible priority system for selected channels is also provided, and the circuitry on both ends of all channels (including the protective channel) is identical to minimize parts inventory costs.