Abstract: A system and a method for constructing a signal integrity supervisor capable of both detecting and triggering an appropriate response when transmit path signals indicate a potential damaging transmitter operating mode. The system and method of the present invention takes advantage of the inherent property of a Delta-Sigma Modulator (DSM) which makes the probability of encountering a long string of consecutive ones or zeroes during nominal operation very small. The signal integrity supervisor ensures safe transmitter operation by monitoring the data and the clock inputs to a digital to analog converter. The system may comprise a data signal supervisor and a clock signal supervisor. The data supervisor may comprise a comparator and a counter and may be configured to power down a line driver upon detecting a data stream having a continuous voltage level.

Abstract: An improved line driver and method for increasing the power efficiency, signal accuracy, and stability of a transmit signal on a transmission line are disclosed. The improved line driver uses a negative feedback control loop, thereby enhancing operational stability and suppressing both amplifier imperfections and discrete component manufacturing variances. Furthermore, when the improved line driver output stage is integrated with a hybrid, the composite circuit provides a power efficient full duplex solution for line driver applications. In a preferred embodiment, the improved line driver may comprise an active line termination control loop with current sense feedback, a first amplifier, and a second amplifier. The present invention can also be viewed as providing a method for increasing the stability, power efficiency, and accuracy of a line driver in a duplex transmission system.

Abstract: A system and a method for constructing a signal integrity supervisor capable of both detecting and triggering an appropriate response when transmit path signals indicate a potential damaging transmitter operating mode. The system and method of the present invention takes advantage of the inherent property of a Delta-Sigma Modulator (DSM) which makes the probability of encountering a long string of consecutive ones or zeroes during nominal operation very small. The signal integrity supervisor ensures safe transmitter operation by monitoring the data and the clock inputs to a digital to analog converter. The system may comprise a data signal supervisor and a clock signal supervisor. The data supervisor may comprise a comparator and a counter and may be configured to power down a line driver upon detecting a data stream having a continuous voltage level.

Abstract: A system and a method for constructing a signal integrity supervisor capable of both detecting and triggering an appropriate response when transmit path signals indicate a potential damaging transmitter operating mode. The system and method of the present invention takes advantage of the inherent property of a Delta-Sigma Modulator (DSM) which makes the probability of encountering a long string of consecutive ones or zeroes during nominal operation very small. The signal integrity supervisor ensures safe transmitter operation by monitoring the data and the clock inputs to a digital to analog converter. The system may comprise a data signal supervisor and a clock signal supervisor. The data supervisor may comprise a comparator and a counter and may be configured to power down a line driver upon detecting a data stream having a continuous voltage level.

Abstract: An improved line driver and method for increasing the available signal transmit power on a transmission line are disclosed. The improved line driver achieves an available transmit power increase without increasing the maximum current in the line driver output stage. The output stage of the line driver may comprise a first amplifier, a second amplifier, and an integrated back-matching resistor network. In order to further increase the available transmit power; a protective semiconductor device may be added to a line driver output stage for each semiconductor device in the first and second amplifiers. A third embodiment of a line driver output stage in accordance with the present invention may comprise a combination of the integrated back-matching resistor network along with the protective semiconductor devices.

Abstract: An improved line driver and method for increasing the available signal transmit power on a transmission line are disclosed. The improved line driver achieves an available transmit power increase by limiting the output stage signal path to NMOS and NPN bipolar semiconductor devices. The output stage of the improved line driver may comprise a first amplifier, a second amplifier, a first transformer, a second transformer, and a plurality of back-matching resistor networks. A second embodiment of an improved output stage of a line driver may comprise a first amplifier, a second amplifier, a transformer, and a plurality of back-matching resistor networks. Both preferred embodiments may be implemented with CMOS and bipolar semiconductor devices, as well as, a combination of the two semiconductor technologies.

Abstract: An improved line driver and method for increasing the available signal transmit power on a transmission line are disclosed. The improved line driver achieves an available transmit power increase without increasing the maximum current in the line driver output stage. The output stage of the line driver may comprise a first amplifier, a second amplifier, and an integrated back-matching resistor network. In order to further increase the available transmit power; a protective semiconductor device may be added to a line driver output stage for each semiconductor device in the first and second amplifiers. A third embodiment of a line driver output stage in accordance with the present invention may comprise a combination of the integrated back-matching resistor network along with the protective semiconductor devices.

Abstract: The present invention is generally directed to a telephone handset for testing the transmission quality of a local loop. In accordance with one aspect of the invention, the telephone handset includes a connector configured to connect to the local loop at, for example, a junction box. The invention also includes a low-pass filter circuit electrically interposed between the connector and operational circuitry of the telephone handset. In operation, the low-pass filter is designed to pass (substantially undisturbed) electrical signals within the POTS frequency band from the connector to the operational circuitry. In the same way, the low-pass filter is designed to substantially block the passage of electrical signals above the POTS frequency range. In this way, the low-pass filter blocks the introduction of high frequency signals, which may otherwise generate intermodulation products within the audible range, from reaching the operational circuitry of the testing handset.

Abstract: The present invention is generally directed to a telephone handset for testing the transmission quality of a local loop. In accordance with one aspect of the invention, the telephone handset includes a connector configured to connect to the local loop at, for example, a junction box. The invention also includes a low-pass filter circuit electrically interposed between the connector and operational circuitry of the telephone handset. In operation, the low-pass filter is designed to pass (substantially undisturbed) electrical signals within the POTS frequency band from the connector to the operational circuitry. In the same way, the low-pass filter is designed to substantially block the passage of electrical signals above the POTS frequency range. In this way, the low-pass filter blocks the introduction of high frequency signals, which may otherwise generate intermodulation products within the audible range, from reaching the operational circuitry of the testing handset.

Abstract: In general, the multi-mode analog front-end provides an internal line driver and hybrid, as well as numerous functions, in order to provide a close to optimum solution for all digital subscriber line applications. The functions provided for by the analog front-end include; programmable hybrid attenuation; onboard amplifiers for driving external transmit and receive filters; a line driver with programmable drive and gain; programmable RC-filters capable of calibration via an internal loop-back under digital control; a programmable switched-capacitor filter for tracking the over sampling rate used by a digital signal processor; internal testing functions; a high frequency boost circuit; a dual input peak detector; selectable data rates; and a programmable data interface. The analog front-end allows for use of particular blocks within the analog front-end particular to the functions necessary to compensate for a particular digital subscriber line application.

Abstract: The present invention provides a switched impedance matching network which may be implemented in a hybrid circuit of a digital subscriber line (DSL) system, or in any other wire-bound communications system for which two-wire-to-four-wire conversion, and vice versa, must be accomplished. In accordance with the preferred embodiment of the present invention, the matching network comprises switchable circuit modules of discrete-valued resistor and capacitor components. Preferably, the circuit modules are assembled into an array of buffered first-order RC circuits. The buffers comprise amplifiers that are switched on or off to control the switching of the circuit modules. The buffer amplifiers also isolate the individual circuit modules from each other and eliminate the need to implement transmission switches between the modules. The switching of the buffer amplifiers clears or blocks the transmission paths between the individual modules, thereby providing the optimum path through the module array.

Abstract: The present invention is generally directed to an xDSL modem that is capable of transmitting at multiple data rates. Specifically, the xDSL modem is configured to generally transmit at a high data rate (typically the highest data rate supported by the line), but will reduce its data transmission rate in response to one or more sensed conditions. In this regard, it has been found that transmitting at a data rate that is low enough to avoid significant corruption, and thus retransmission, achieves a higher overall data transmission rate than that which is achieved if re-transmissions are required. Further, various conditions may be sensed that will prompt the xDSL modem to alter its transmission rate, including detecting an unfiltered POTS device going Off-Hook. In accordance with one aspect of the present invention, at modem startup, the Off-Hook condition and other line problems are detected by direct measurement of the line impedance.

Abstract: The present invention entails a circuit and method for determining the distortion created by a transformer used in data communications. The circuit according to the present invention comprises a transmitting circuit, a back matching circuit, and a subtracting circuit. The transmitting circuit generates a test signal to be transmitted into a transformer, the transmitting circuit having a transmitting output for coupling to a transformer. Once applied to the transformer, the test signal is distorted by the transformer, where the transformer creates harmonics of the test signal and other signal distortion. The back matching circuit generates a scaled test signal that is subtracted from the distorted test signal in the subtraction circuit. The result is a diminished peak at the test signal in comparison to the harmonics such that the distortion by the transformer can be determined using a measuring device with a relatively low dynamic range.

Abstract: An line interface circuit at a central office of a telecommunication system provides improved noise immunity to a ring signal. In accordance with one aspect of the invention, the line interface circuit includes a signal line having a first end for connection to a ring signal generating source and a second end for communication with a customer premises via a local loop. A POTS filter is electrically connected to the signal line. Preferably, the POTS filter is a relatively simple and thus inexpensive low-order filter, which may be implemented as a simple L-C circuit. The preferred embodiment of the present invention further includes a POTS communication device electrically connected to the signal line at a point between the POTS filter and the first end. In this regard, the POTS communications device broadly denotes any device designed to communicate information within the POTS frequency band, such as a telephone (e.g., voice information), a facsimile machine, a PSTN modem, etc.

Abstract: A system and method for a communication to communicate both POTS and XDSL are provided. In accordance with one aspect of the invention, in improved central office line card circuit is provided, wherein the line card circuit includes a two-wire signal line for electrical connection with a two-wire local loop. A line interface card interfaces with the local loop and includes a bi-directional line for bi-directional communication with the signal line. In addition, the line interface circuit further has an input line and an output line. A first channel has an output electrically connected to the input line of the line interface circuit, and the first channel has inputs for both a pulse code modulation (PCM) input and a xDSL input. Similarly, a second channel has an input that is electrically connected to the output line of the line interface circuit. In addition, the second channel has outputs for both a PCM output and a xDSL output.