Abstract: A synthetic impedance line driver for driving a telecommunication line includes a complementary operational amplifier pair having cross-coupled positive feedback summing resistors. The driver circuit is configured to provide a relatively large multiplication of the values of relatively small valued output resistors to realize a synthesized impedance matching that of the driven line. A cross-coupled resistor network may be employed to cancel out far end signal components present in an analog canceler drive signal. The values of the auxiliary network resistors are ratioed such that the signal at nodes between resistors of branches of the network is a fraction of the open circuit voltage swing of the amplifiers, with far end signal components canceled.

Abstract: An analog input to an interpolation scheme for a digital signal processing receiver is digitized by an oversampling sigma-delta modulator running at a clock frequency that is a multiple of the nominal baud rate. The digitized signal sample stream and a delayed version thereof are shifted through finite impulse response (FIR) filters. The outputs of the FIR filters are coupled to a linear interpolator at a time determined by a carry-out of a divide-by-M counter, so as to decimate the digitized inputs to the FIR filters by the ratio of the oversampling clock to the baud clock. The control path to the interpolator includes a digital phase locked loop containing a linear canceler, to which data from an echo canceler and data decisions from an equalizer are supplied, and from which a timing error input is supplied to a loop filter.

Abstract: An arbitration mechanism is distributed among channel units of a statistically multiplexed frame relay switching system serving a plurality of access lines, the cumulative bandwidth of which exceeds that of an aggregate data link over which data is to be transported. For each access line, an arbitration code is generated. This code includes a transmit request or start bit, a calculated multibit arbitration value based upon a combination of parameters, including queuing delay and the configuration and traffic rate of the line, and an address code that identifies the physical location of the respective channel unit. All arbitration codes are readable by each frame relay channel unit via a wire-ORed bus. A channel unit participating in an arbitration cycle compares the value of its arbitration code with those of the other participants.

Abstract: A software-based automated DS0 channel format analysis routine resident in a U-BRITE interface card's microcontroller solves the problem of potential misconfiguration of ISDN interface circuit cards, as may result from the failure to properly set DS0 time slot option switches to their intended ISDN channel assignments. When exercised, the routine automatically determines not only what DS0 channels are available at the remote ISDN circuit card, but also the order in which those DS0 channels are multiplexed by that remote card's circuitry. As a consequence, once the routine has run to completion, each ISDN interface card will contain the same DS0 time slot multiplexing scheme—corresponding to what has been manually configured at a remote card—even if the remote card's DS0 option switches were originally incorrectly set.

Abstract: In a data communication system having a channel with time-varying impairments and further having a transmitter with a precoder, a method and apparatus for updating the precoder coefficients. The method and apparatus is based on the arrangement of a duplicate precoder and correction filter in the receiver, where the correction filter generates incremental coefficients. The incremental coefficients are sent via a back channel to the transmitter and added to the current values of the precoder coefficients. The method and apparatus provide DFE-like performance and do not have the delay problems associated with DFEs.

Abstract: In order to ensure continuous telephone service to a customer premises served by an ISDN line, without requiring that the customer maintain an additional POTS line as an emergency back-up to the normally used ISDN service, ISDN signalling circuits and network termination interface components are modified, so that, in the event of a loss of power to customer premises digital communications equipment, a communication link between an auxiliary POTS telephone and the normal ISDN communication path to the central office may be established. There need not be any modification of the central office switch, per se, so that the integrity of the ISDN communication path with the central office line card remains unaffected. As a result, the central office equipment can continue to conduct standard ISDN communications with the customer premises equipment, even though the customer is employing a POTS back-up analog phone.

Abstract: A multi-circuit emulating line card is installable in a single line card slot of the backplane of digital switch, and is configured to emulate the functionality of each of a plurality of digital switch line cards, respectively associated with plural digital subscriber circuits served by the switch. In the course of emulating these plural line cards, the multi-circuit line card provides connectivity between each digital subscriber circuit and a digital carrier communication link to plural digital subscriber loop circuits, such as BRITE cards of a remote terminal site. The line card of the invention also includes network and subscriber circuit-associated metallic link impedance simulation circuits for terminating a metallic test bus.

Abstract: The present invention relates to an improved method and apparatus for echo cancellation in a communication system utilizing a bidirectional transmission medium. The invention significantly reduces computational overhead associated with echo cancellation by using sub-Nyquist sampling in the echo path. In particular, the invention relates to a method and apparatus for echo cancellation in a communication system utilizing different signaling or baud rates in the transmit and receive directions, whereby the computational overhead of the echo cancellation is significantly reduced as compared to traditional methods. In a preferred embodiment herein, the present invention reduces by one-half the computational overhead associated with echo cancellation in a data communications system utilizing symmetrical information rates at asymmetrical signal rates.

Abstract: A loop loss measurement and reporting mechanism for a digital data services unit obviates interaction with a test unit at a far end of the loop, by relying upon a priori knowledge of the signal power and spectral content of a data port at the far end of the loop to conduct threshold detection and power level measurements. A received signal is amplified by amplifier circuitry, the gain of which is controllably adjusted by the microcontroller based upon the outputs of threshold detectors and power level measurement circuitry that monitor the amplified received signal. A front panel display is controlled by the microcontroller to display loop loss parameter information. To measure and report loop loss, the digital data services unit turns off its transmitter for a prescribed period of time and monitors an in-band signal of known power and spectral content sourced from the far end of the loop.

Abstract: An automated telecommunication switch type and protocol detection routine transmits an interrogation message to a telecommunication switch. The contents of the interrogation message are such as to cause the switch to transmit a response message that uniquely identifies only one switch protocol and switch type. Once switch type and protocol have been automatically determined, this information may be coupled with an automated service profile identifier (SPID) detection mechanism to facilitate generation of the requisite SPID(s).

Abstract: The present invention is a communication system for communicatinginformation over greater distances than otherwise possible on bidirectional media subject tointerference, by reducing the interference while assuring spectral compatibility with other communication services. The system of the present invention provides symmetric data service to end users by using asymmetric signaling. In one embodiment, the present invention utilizes partially overlapped, non-symmetric baud rates and spectrally shaped transceiver filters to achieve both spectral compatibility and extended range.

Abstract: A universal digital communication device includes a first digital communications interface for a first type of digital communication signals (such as basic rate 2B1Q ISDN signals), and a second digital communications interface for a second type of digital communication signals (such as extended range 3B1O ISDN signals) having a digital transport range over a telecommunications network greater than that of the first type of digital communication signals. A processor-controlled multiplexer unit determines which of the two types of digital communication signals is required for providing digital communication connectivity between local and remote communications equipment. It then couples the terminal equipment to the telecommunications network by way the digital communications interface that is capable of interfacing the required digital communication signals with the telecommunication network.

Abstract: An analog input to an interpolation scheme for a digital signal processing receiver is digitized by an oversampling sigma-delta modulator running at a clock frequency that is a multiple of the nominal baud rate. The digitized signal sample stream and a delayed version thereof are shifted through finite impulse response (FIR) filters. The outputs of the FIR filters are coupled to a linear interpolator at a time determined by a carry-out of a divide-by-M counter, so as to decimate the digitized inputs to the FIR filters by the ratio of the oversampling clock to the baud clock. The control path to the interpolator includes a digital phase locked loop containing a linear canceler, to which data from an echo canceler and data decisions from an equalizer are supplied, and from which a timing error input is supplied to a loop filter.

Abstract: A multi-circuit emulating line card is installable in a single line card slot of the backplane of digital switch, and is configured to emulate the functionality of each of a plurality of digital switch line cards, respectively associated with plural digital subscriber circuits served by the switch. In the course of emulating these plural line cards, the multi-circuit line card provides connectivity between each digital subscriber circuit and a digital carrier communication link to plural digital subscriber loop circuits, such as BRITE cards of a remote terminal site. The line card of the invention also includes network and subscriber circuit-associated metallic link impedance simulation circuits for terminating a metallic test bus.

Abstract: Frequency synthesizers of a radio transceiver are automatically tuned so that its transmit and receive frequencies correspond to whichever upper band and lower band filters the radio transceiver has been connected by the user. A capacitive electrical impedance interface is coupled to filter circuitry of an upper band filter section, while an inductive electrical impedance interface is coupled to filter circuitry of the lower based filter section. A voltage reference circuit is coupled to one of the transmit port and the receive port of the transceiver. A controller is operative to automatically tune the transceiver to transmit in one of the upper and lower frequency bands, and to receive on the other frequency band, in accordance with the voltage level generated by the voltage reference circuit.

Abstract: A composite circuit card architecture conforms with a prescribed form factor for installation in a card slot and connection to a backplane of a multiple circuit card-supporting housing. Only a portion of the card is comprised of printed wiring board material, while the remainder, where no printed circuit components are installed, is a support substrate formed of a material other than that of said printed wiring board. Also, a front panel portion is formed of the material other than that of the printed wiring board, such as plastic integrally molded with the support substrate, thereby significantly reducing the cost associated with the conventional approach of making the entire card from printed circuit board material. At one communication link, such as a ribbon cable, may be coupled between the printed wiring board and at least one input/output port at the front panel.

Abstract: A channel interface architecture for a time division multiplexed (TDM) data communication system has a plurality of TDM communication ports coupled to serial TDM communication channels. The channel interface architecture interfaces data from any channel of any TDM communication port with any TDM communication channel of any other TDM communication port, on a per time slot/channel basis. The architecture includes a parallel data bus portion, an address bus portion, and a control portion. Each of a plurality of TDM communication channel interface units, associated with the ports, includes a multipage memory that stores data received from an associated serial communication link. The memory also selectively stores data that has been asserted onto the data bus portion of the bus architecture from another interface unit.

Abstract: The inability of an ISDN equipment user to properly configure ISDN terminal equipment, even when provided with correctly assigned switch protocol, SPID and LDN parameters by a telephone service provider, is successfully remedied by a SPID/switch protocol detector. Upon being invoked by the user, the routine proceeds to conduct an iterative search of stored SPID formats associated with different central office switch protocols. SPIDs are assembled in accordance with the iteratively accessed SPID formats and directory number information that has been entered by the user. If an attempt to register a SPID is successful, the routine places a test call. If the test call is successful, the SPID and its associated switch protocol will have been identified, and the terminal equipment may place a call.

Abstract: An auto-SPID detection routine is operative to conduct an iterative search of stored SPID formats associated with different central office switch protocols, based upon directory information including an area code supplied by a user. If an attempt to register a SPID is successful, the routine places a test call. If the test call is successful, the SPID and its associated switch protocol will have been identified, and the terminal equipment may place a call. If an attempt to register a SPID is unsuccessful, a determination is made as to whether the area code is a subdivided or split area code. If so, the routine is reexecuted using another area code derived from a split area code table.