Abstract: A channel interface unit for interconnecting a two-wire transmission path which transmits analog signals and a digital signal transmission path. The channel interface unit includes a digital interface unit coupled with the digital signal transmission path and producing digital signals based on digital signals received from the digital signal transmission path, a converter for converting the digital signals to analog signals, a filter for removing noise, produced by the converter, from the analog signals, a driver, coupled with the two-wire transmission path, for amplifying the filtered analog signals, and a power supply for providing regulated voltage to the driver The channel interface unit also includes a device for decreasing effective capacitance by modifying the output impedance of the driver.

Abstract: A channel interface unit for interconnecting a two-wire transmission path which transmits analog signals and a digital signal transmission path. The channel interface unit includes a digital interface unit coupled with the digital signal transmission path and producing digital signals based on digital signals received from the digital signal transmission path, a converter for converting the digital signals to analog signals, a filter for removing noise, produced by the converter, from the analog signals, a driver, coupled with the two-wire transmission path, for amplifying the filtered analog signals, and a power supply for providing regulated voltage to the driver.

Abstract: A channel interface unit for interconnecting a two-wire transmission path which transmits analog signals and a digital signal transmission path. The channel interface unit includes a digital interface unit coupled with the digital signal transmission path and producing digital signals based on digital signals received from the digital signal transmission path, a converter for converting the digital signals to analog signals, a filter for removing noise, produced by the converter, from the analog signals, a driver, coupled with the two-wire transmission path, for amplifying the filtered analog signals, and a power supply for providing regulated voltage to the driver.

Abstract: A system is disclosed for verifying the integrity of each one of a number of communication paths, illustratively telephone subscriber loops, that runs between a near end location, illustratively a telephone company central office, and a corresponding remote ("far end") location(s). This system utilizes circuitry, such as a line verification module, that is located at the far end of each path to impart a selected test signal specifically a selected one of a number of sub-audible frequencies, thereto. In one embodiment, the circuitry continously transmits a test signal over the path. The level of the test signal is automatically adjusted such that this signal remains at an approximately constant amplitude regardless of whether that path is in an on-hook or off-hook condition. Central office monitoring circuitry is connected to the near end of every path being verified.

Abstract: A system is disclosed for verifying the integrity of each one of a number of communication paths, illustratively telephone subscriber loops, that runs between a near end location, illustratively a telephone central office, and corresponding remote ("far end") location(s). This system utilizes circuitry, such as a line verification module, that is located at the far end of the path to detect one or more conditions thereat (e.g. loop current and loop voltage) that are indicative of normal operation of the path, e.g. proper on-hook and off-hook conditions. As long as the path is normally operating at the far end, this circuitry would then transmit a test signal, e.g. a selected one of a number of sub-audible frequencies, over the path to the near end. This test signal is chosen to be substantially transparent to normal communication (e.g. local telephone company signalling and transmission frequencies) occurring over that path.