Abstract: Apparatuses and techniques are described for calibrating a negative voltage source. A ground voltage is applied to a multi-stage amplifier from the negative voltage source while an offset voltage measurement (OVM) is made at the output of the multi-stage amplifier. The OVM is recorded and subsequently used by a calibration circuit when the negative voltage source applies a range of negative voltages to the input of the multiple stage amplifier. The calibration circuit subtracts the OVM from measurements obtained at the output of the multi-stage amplifier to obtain corrected measurements, and uses the corrected measurements to calibrate the negative voltage source, e.g., by adjusting a relationship between digital values input to the negative voltage source and the output voltages.

Abstract: An induced loss value is retrieved from a configuration file of an MTA device. The loss value is provided to a signal generator that generates call progress/alerting signals and FSK signals in the MTA telephony device. To mitigate the imbalance between incoming voice signal levels and call progress/alerting signals that may occur because the call progress/alerting signals are not generated at a level equal to that of the incoming voice signals, the loss/attenuation amount from the configuration file is used to adjust the levels of the generated call progress/alerting and FSK signals by a corresponding amount before they are attenuated along with the incoming voice signals.

Abstract: Various systems and methods for probing a communication channel. These systems and methods transmit an error vector probe packet from a first transmitter while a second transmitter is active and transmitting. A network device may receive the error vector probe packet and measure an error vector magnitude based on the received error vector probe packet. Using the error vector magnitude, the network device estimates channel characteristics such as signal-to-noise ratio, data capacity, etc. The transmission can occur when more than one transmitter is active and transmitting. At least some of the other transmitters are active and transmit an analog zero signal, e.g., all digital zeros on the input to the digital-to-analog converter of a network device when an error vector probe packet is transmitted.

Abstract: An internet protocol telephone includes a substrate having an input and an output that are capable of being connected to the internet protocol (IP) network. A relay is disposed on the substrate and is connected between the input and the output of the substrate. The relay includes first and second native FETs that have a threshold voltage of approximately zero volts. Therefore, the relay is nominally turned-on, even when little or no voltage (or power) is applied to the IP telephone substrate, as during the discovery mode of IP telephone operation. During discovery mode, The IP phone is configured to be responsive to extended link pulses and block data packets that are associated with legacy devices. Data packets have a higher signal duration and are more continuous than extended link pulses. The IP phone includes a switchable ground that is connected to the gates of the native devices, and is controlled by a rectifier and filter circuit that are connected to the substrate input.

Abstract: A system and method for measuring a characteristic impedance of a transmission-line comprises transmitting energy to the line, and shortly after measuring the voltage/current involved and thus measuring the equivalent impedance. The measured characteristic impedance may then be used in order to determine the termination value required to minimize reflections. In another embodiment, the proper termination is set or measured by adjusting the termination value to achieve maximum power dissipation in the terminating device. The equivalent characteristic impedance measurement may be used to count the number of metallic conductors connected to a single connection point. This abstract is not intended to limit or construe the scope of the claims.

Abstract: A method for controlling a ringing signal includes generating a ringing signal on a subscriber line, detecting a condition indicative of the subscriber line going off-hook and reducing an amplitude of the ringing signal responsive to detecting the condition. A line card includes a subscriber line interface circuit operable to generate a ringing signal on a subscriber line and a subscriber line audio-processing circuit operable to detect a condition indicative of the subscriber line going off-hook and reducing an amplitude of the ringing signal responsive to detecting the condition.

Abstract: A hybrid circuit without inductors is provided. Embodiments can be used in high-speed communication devices, including Cable modem and Digital Subscriber Line (DSL) devices. In particular, embodiments can be used in Very High Speed DSL (VDSL) devices. Embodiments provide a cheap and compact solution to the echo rejection problem in high-speed communication devices. Furthermore, embodiments perform at least comparably to conventional solutions with respect to key performance measures.

Abstract: In one embodiment, the present invention includes an apparatus having a first pair of low voltage operational amplifiers to generate an output representative of an absolute value difference of first and second line voltages of a subscriber loop, and a third low voltage operational amplifier having an input coupled to the output of the first pair of low voltage operational amplifiers to filter the output and to provide a switch control signal for a switching regulator that provides a voltage used to generate the first and second line voltages. The apparatus may include additional circuits such as a limit circuit to limit the input to the third low voltage operational amplifier and one or more speedup circuits to reduce a filter time constant of the third low voltage operational amplifier during a ringing mode of the subscriber loop.

Abstract: A method of signal communication includes receiving a selection signal, and selecting a selected frequency range used for a multi-carrier signal communication from a set of predetermined frequency ranges for signal communication depending on the selection signal. The set of predetermined frequency ranges includes a first frequency range and a second frequency range including the first frequency range.

Abstract: A line state detecting apparatus provided in a balanced transmission system includes, in transmission lines comprising a pair of conductors W1, W2 connected to a transmitting portion 13, current transformers T11, T12 primary sides of which are inserted to respectives thereof in series therewith and secondary sides of which are connected in series to cancel currents or voltages of the two transformer by each other, and a detecting portion 11 for detecting currents or voltages on secondary sides of the current transformers T11, T12. By an output of the detecting portion 11, a difference of currents or voltages of the conductors W1, W2 of the transmission lines is provided and an unbalance component between the conductors W1, W2 is detected.

Abstract: A monitor access is gradually applied an removed from a communications circuit, including a digital subscriber line (DSL), by a gradual monitor access (GMA) technique, in which a variable impedance element is gradually applied to the communications circuit until the monitor can be introduced to the communications circuit without data disruption.

Abstract: A telephone interface circuit comprising a speech circuit, a control circuit turning on upon receiving a supply of a forward direction trigger current so as to connect first and second telephone lines and the speech circuit, and going off upon receiving a supply of a reverse direction trigger current so as to disconnect the first and second telephone lines and the speech circuit, a capacitor charging and discharging charge supplied from the first telephone line, and a hook switch supplying charge accumulated at the capacitor when off-hook to the control circuit as a forward direction trigger current, and supplying charge discharged from the capacitor when on-hook to the control circuit as a reverse direction trigger current.

Abstract: A method of calibrating longitudinal balance for a subscriber line interface circuit includes providing a first and a second driver of a differential driver pair for driving a subscriber line. An output of each of the first and second drivers is coupled to a common output. The common output is coupled to an input of the first driver. The gain of at least one of the first and second drivers is adjusted until a calibration signal (V1) present at the input of the first driver is substantially the same as a calibration signal (V2) present at the input of the second driver.

Abstract: A system processes signals exchanged between a near end terminal and a far end terminal over a communication path. The system selects the processing characteristics of a near end terminal based on characteristics of the communication path. The communication path may include the near and the far end terminal and their respective codecs, and the networks. The system may select processing characteristics of the near end terminal based on characteristics of the communication path. Selecting the processing characteristics may include selecting a predetermined operation. The system may adapt a selected operation based on a real time analysis of the communication path.

Abstract: A line interface capable of connecting to a variety of transport mediums, each having a different impedance. The line interface comprises a programmable resistor. The programmable resistor along with an external resistor provide a range of resistor values which are used to substantially match the impedance requirements of the various transport mediums.

Abstract: A system and method to reduce echoes in voice communications are described. Input data containing return loss values of a communication trunk within a communications network is received, the return loss values being measured at each frequency of a plurality of frequencies within a predetermined frequency band. An optimum transhybrid balance impedance is calculated from the input data. Finally, the optimum transhybrid balance impedance is transmitted to a user for further processing.

Abstract: A communication apparatus is used to interface signals with any one of a plurality of telephony networks having different impedances. The apparatus includes memory, a processor, a digital-to-analog (D/A) converter, and an interface port. Different sets of impedance control values are stored in the memory. The processor is configured to select one of the sets of impedance control values and to serially transmit the selected set of impedance control values during a communication session. The D/A converter is configured to receive the selected set of impedance control values from the processor and to transmit analog signals based on the selected set of impedance control values. The interface port is configured to interface signals with a communication connection of a telephony network.

Abstract: A cordless telephone-to-sound card interface adapter provides a connection between any standard cordless telephone system and a sound card of a computer for PC-to-PC or PC-to-telephone voice communications over the Internet. The interface adapter includes a hybrid transformer circuit for interfacing a two-wire circuit of the cordless telephone and a four-wire circuit of the computer sound card. Consisting of passive components, this hybrid transformer circuit cancels out the voice echo that would otherwise exist due to mismatched impedances between the two media and/or from leakage of the signal being transmitted and received on the same pair of telephone lines. Preferably, a Universal Serial Bus (USB) interface is provided to supply a bias voltage to the cordless telephone system through the interface adapter.

Abstract: A method and system for remotely calibrating a headset telephone with a reliable, accurate and easy to use user interface is provided. This method makes use of the remote programmability of advanced telephone headsets and DTMF signal encoding and permits the customer-user to instigate the calibration procedure with an ordinary telephone call. The invention provides a way for the optimum settings to be transmitted, loaded and stored to the headset, thereby improving the audio quality of telephone headsets by providing adjustment steps for such audio qualities as microphone gain, speaker gain, background noise and echo cancellation, filter functions and diagnostics.

Abstract: A communication system is provided which draws virtually no loop current during a ringing burst and only draws on-hook loop current during the caller ID field. More particularly, ringer burst circuitry may be powered from the user powered circuitry by the transmission of power across the isolation barrier rather than being powered from the phone line. Thus, loop current need not be drawn from the TIP/RING lines during ringer bursts. The isolation barrier may be a capacitive isolation barrier which allows bidirectional communication and extraction of power from signals transmitted across the barrier.

Abstract: Echo cancelling in a communication line system, particularly an ISDN or XDSL system, is performed with a tunable hybrid having tunable passive elements. The tunable hybrid is integrated in the analog front-end portion of the communication line system. The values of the tunable passive elements are digitally controlled by a microprocessor.

Abstract: A digital direct access arrangement (DAA) circuitry may be used to terminate the telephone connections at the user's end to provide a communication path for signals to and from the phone lines. Briefly described, a means for providing a proper hookswitch transition for a variety of international phone standards is provided. The invention may also be utilized with means for transmitting and receiving a signal across a capacitive isolation barrier. More particularly, a DAA circuitry may be utilized which satisfies many or all hookswitch transition standards without the use of additional discrete devices. The hookswitch transition standards may be satisfied by ramping down the current flowing through the hookswitch prior to transitioning the hookswitch state. In this manner the hookswitch current change as a function of time (di/dt) may be decreased. Thus, the current through the hookswitch may be actively controlled prior to switching the hookswitch from an off-hook condition to an on-hook condition.

Abstract: An improved line driver-hybrid 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-hybrid uses a negative feedback control loop, thereby enhancing operational stability and suppressing both amplifier imperfections and discrete component manufacturing variances. Furthermore, the improved line driver-hybrid provides a power efficient full duplex solution for line driver applications. The present invention can also be viewed as providing a method for actively terminating a transmission line.

Abstract: A subscriber line driver (SLD) is provided for the continuous and automatic transformation of the characteristics of a communication system signal so that the signal conforms to a power spectral distribution (PSD) standard. The signal is transformed by the SLD which may increase (amplify) portions of the signal to a predefined specification, decrease (attenuate) portions of the signal to a predefined specification, and/or frequency modulate or filter the transmit signal frequencies to fit within the communication channel frequency bandwidth as defined by a predefined frequency band. After modification by the SLD, the transformed communication signal is injected (transmitted) into a communication transmission line. An SLD device can be employed in a variety of communication systems such as a public telephony system, a private branch exchange (PBX), a coaxial cable system, a fiber optic system, a microwave system, a radio communication system or the like.

Abstract: Disclosed herein are swizzling techniques that may provide capacitive and inductive noise cancellation on a set of signal lines. Positive noise due to a capacitive coupling between attacker signal lines and near victim signal lines is, in part, cancelled by negative noise due to inductive coupling between the attacker signal lines and a far victim signal line. Repeatable swizzling patterns are set forth to transpose near victim signal lines and far victim signal lines in subsequent segments to facilitate the capacitive and inductive cancellation. The signal lines are optionally reordered by a final swizzling to restore the set's original ordering.

Abstract: A CODEC and a SLIC assembly perform current-sensing-voltage synthesis impedance matching and DC feed control functions. Signal processing that does not require high voltage, such as impedance matching and DC feed control, is performed in the digital domain by the CODEC while the SLIC assembly includes high voltage circuitry. This configuration is useful for Voice over Internet Protocol (VOIP) applications with a short subscriber line loop or other long loop applications. The SLIC includes high voltage operational amplifiers (op amps) to drive ring and tip signals. Bipolar transistors are also provided as bias compensating diodes for bias point stabilization over dynamic operating conditions such as temperature. The high voltage op amps include a composite MOSFET-bipolar complimentary symmetry driver stage that offers the bias control and stability of a bipolar device topology and drive capabilities of a power MOSFET device.

Abstract: The present invention provides apparatus and methods for attenuating signals received from a source over a data transmission line, having an unknown resistance, to achieve optimized signals in various data terminal and data communications equipment. In a preferred embodiment, a resistor network is operably coupled between the transmission line and a means for processing the signal, such as a digital processor, an ADC and a DAC. The resistor network comprises a termination resistor that is associated with a termination voltage, a variable resistor and another resistor. During use, a switch is operably positioned between a plurality of switch positions so that two voltage measurements will lead to the determination of the voltage of the source and the termination voltage within the resistor network. Once these voltages are known, the unknown resistance can be estimated.

Abstract: An automatic gain control apparatus, employed in a communication system having a circuit that interfaces a two-wire line to a four-wire line, measures the echo return loss occurring at the interface, calculates a gain from the echo return loss, and amplifies an incoming signal on the four-wire line by the calculated gain before transmission through the interface, to compensate for the echo return loss. If the communication system uses an echo canceler to cancel the echo, the echo canceler is preferably shielded from the effects of automatic gain control, by attenuation of the outgoing signal on the four-wire line, for example.

Abstract: A digital line-interface circuit (100) presents a constant impedance to a telephone line (102) by emulating a short or a ground connection between the leads of the telephone line when the transmitter (104) is disabled. The receiver (106) includes a pair of differential op amps (U3, U4) connecting the receive line (122) to the outputs of the transmitter's drivers (U1A, U2A) across a pair of switches (K1, K2). The switches may be replaced by a receive enable (RE) signal line connected to enable (EN) inputs of the op amps. Negative inputs of the op amps are connected to outputs of different transmitter drivers, positive inputs of the op amps are connected to a bias voltage source (Vbias), and the output of each op amp is connected to the receive line and is also fed back by a bias resistor (R5, R6) to its negative input.

Abstract: A fixed wireless terminal such as a wireless local loop terminal comprising: memory (210) storing characteristics for at least one network, means (214, 220) for accepting network information particular to a subscriber and processing means (208) for reading the subscriber network information and, on the basis of the subscriber network information, selecting appropriate network characteristics for subsequent use by the terminal. Preferably the processing means (208) is arranged to configure a subscriber line interface circuit (212) in accordance with the selected appropriate network characteristics, such as ringing tone, dialling tone, busy tone etc.

Abstract: A line terminal circuit comprises a buffer section (A, D) for connection to a transmission line (TL) and for performing at least one of the functions receiving signals from said transmission line and transmitting signals via said transmission line; a controllable current source section (S1, S2) connected to inject or withdraw a current (Iu, Id) into or from a node (ND1, ND2) between said buffer section and said transmission line in accordance with a current control signal (CS); and a common mode voltage control section (CT) for detecting a common mode voltage component on the transmission line (TL) connected to the buffer section (A, D) and for generating said current control signal (CS) in response to said detected common mode voltage component and outputting said current control signal to said current source section (S1, S2); said common mode voltage control section (CT) being adapted to output said current control signal (CS) such that said common mode voltage component is within the limits of a predetermi

Abstract: A method and system for providing suppression of near-end speech energy for tone signal detectors. In accordance with the invention a system or device is connected between the tip and ring on a subscriber loop, the subscriber loop being connected to office equipment and that subscriber's station set. The system also includes a receive interface that is connected to either a tone signal detector or a frequency shift keying modulator. The system achieves speech cancellation by forming a Wheatstone bridge with a mirror circuit possessing a scaled image of the loop and office equipment impedance. In one embodiment of the invention the Wheatstone bridge is formed using the combined impedance of the loop and office equipment as the impedance that is to be matched by a set of balanced networks included within the system.

Abstract: Line circuits can be supplied with a first voltage or a second voltage of a lower absolute value. At least the second voltage is variable. The line voltages of at least active line circuits are measured, and possible values for the second voltage are prognosticated. It is determined which line circuits can be supplied with the respective possible value, and the power consumption of those line circuits is calculated using each possible value. For the line circuits which cannot be so supplied, the power consumption is calculated using the first voltage. For each possible value prognosticated for the second voltage, the total power consumptions are summed, and the value that gives the lowest total power consumption is selected as the second voltage. The line circuits are then supplied with the first voltage or the selected second voltage.

Abstract: A splitter separates telephony traffic (POTS) from digital subscriber line (ADSL) traffic occupying a higher frequency band. The splitter comprises a low-pass filter for passing the telephony traffic, the low-pass filter being operable to vary its filtering response between a first low-pass response for use during telephony speech traffic, and a second, more restrictive, low-pass response for use during at least part of the time that telephony signalling traffic is present. During speech traffic a filter is used which provides a good impedance match with a telephony terminal or linecard so as to minimize detrimental effects on sidetone and echo performance which may impair a user's speech quality. The filter response can be varied according to a detected property of the telephony traffic, such as amplitude or rate of change of amplitude of the traffic.

Abstract: A two-wire line conditioning apparatus utilizing dial tone for alignment. Variable impedances are iteratively adjusted using a multitone calibration signal. The hybrid device filters out dial tone components in measuring the echo of the multitone signal during the variable impedance adjustment. The level of the dial tone is measured to determine the overall gain that is to be inserted on the line by the line conditioning apparatus.

Abstract: A method and system for remotely calibrating a headset telephone with a reliable, accurate and easy to use user interface is provided. This method makes use of the remote programmability of advanced telephone headsets and DTMF signal encoding and permits the customer-user to instigate the calibration procedure with an ordinary telephone call. The invention provides the means by which the optimum settings can be transmitted to the headset, loaded and stored in the headset, thereby improving the audio quality of telephone headsets by providing adjustment steps for such audio qualities as microphone gain (transmit level), speaker gain, background noise and echo cancellation, filter functions and diagnostics. This method also provides audio feedback to a customer service representative performing the calibration to insure that the commands and adjustments were properly received.

Abstract: An interface for coupling a modem port with a transmission line includes a hybrid converter having a variable gain amplifier coupling a transmit path of a first differential polarity and a received path of a second differential polarity.

Abstract: An adjustable balancing circuit (900) for an adaptive hybrid is suitable for use with a two-conductor transmission line in full duplex communications. In a preferred example, the adjustable balancing circuit (900) includes a first impedance structure (902), a second impedance structure (904), a plurality of N resistor-inductor-capacitor (RLC) networks (908), a first plurality of N switch circuits (912), and a second plurality of N switch circuits (914). The first plurality of N switch circuits (912) switchably cascadingly couples the first plurality of N RLC networks (908) to a first end of the first impedance structure (902). The second plurality of N switch circuits (914) switchably couples a first end of the second impedance structure (904) to a first end of each RLC network. When properly configured, the adjustable balancing circuit (900) cancels reflected transmit signals caused by the presence of short bridged taps on the two-conductor transmission line.

Abstract: Methods and apparatus for providing temperature compensation for a communications card, such as a modem or network card, to minimize retrain sequences between the communications card and another communications card during periods of temperature build-up within the communications card are disclosed. It is a feature of the invention to provide this temperature compensation regardless of the speed or temperature of arriving at a steady state temperature and regardless of the make of the communications card, host computer or computing temperature environment under examination. In a preferred embodiment, a keyword between the communications card and a host computer is compared to provide unique heat compensation for these two devices that have generally different, but consistent, heating characteristics.

Abstract: Apparatus for interconnecting the Tip and Ring telephone line interface to subsequent communications equipment or circuits through a differential line bridge circuit that extracts one or more unidirectional paths containing predominantly far-end energy, wherein, near-end speech signals have been canceled. The differential line bridge circuit maintains the longitudinal balance of the telephone line and exhibits improved noise immunity in the recovered far-end signal. It permits all telephone supervisory, alerting and bidirectional communication signals to pass transparently between the telephone line interface and the subsequent communications equipment or circuits. Access to on-hook service signals, such as calling party identification and short text messaging data transmissions, is inherently provided by the line bridge.

Abstract: An emergency reporting apparatus for a vehicle includes a memory storing information representing a telephone number of an emergency report receiving center. Connection with the emergency report receiving center is implemented in response to the telephone number represented by the information in the memory. An emergency can be reported to the emergency report receiving center. The information in the memory can be updated to change the telephone number represented thereby.

Abstract: The present invention provides a two-wire line conditioning apparatus having an improved calibration and cancellation circuit and provides an improved calibration method using a multitone calibration signal. The apparatus automatically adjusts an electronic hybrid as part of a calibration procedure so as to eliminate undesirable echo effects when calls are placed along the line. The alignment procedure identifies the optimal balance in a rapid manner. The electronic hybrid balancing process and echo cancellation circuitry may also be utilized in a circuit for converting four-wire communications systems to two-wire communications systems. The line conditioning device of the present invention utilizes a multitone signal to simulate the voice frequency spectrum between approximately 500 Hz and 3500 Hz to probe the line side with a plurality of tones (e.g., 500, 1500 and 3500 Hz; or 500, 1000, 1500, 2000, 2500, 3000, 3500 Hz).

Abstract: A device connected to a base of a telephone system by four wires. The device determines the manner in which the wires are used during transmission and reception of electrical signals representing communications. A user places the telephone system in a receive-only mode and provides an indication to the device. The device examines the wires to determine which of the two wires are being used for reception, and the voltage level which is used for receiving the signals. The remaining two wires are deemed to be used for transmission of electrical signals. Communication may be established with an external calibration system to calibrate the transmission and receive voltage levels. The determined information can be used in several environments such as for secure communication for voice and data.

Abstract: A current-limiting circuit (110) of a battery-feed circuit (FIG. 1) for a digital telecommunications line (T,R) provides a low start-up current limit (I3) when power is initially applied to the digital line. It automatically and gradually changes (40) to a high current limit (I1) as the load on the line is charged. When the load is fully charged, the circuit provides a low impedance to the line. Upon occurrence of a fault, the circuit switches back to the initial low current-limit state. The circuit comprises a feed transistor (Q1, Q11), a control transistor (Q2, Q12), and a high-impedance resistive circuit (R1-R4, R15). The feed transistor limits (403) current flowing to the R lead of the line to the high limit when the voltage across the feed transistor is low (0-V2) and the feed transistor is saturated.

Abstract: The present invention provides a two-wire line conditioning apparatus having an improved calibration and cancellation circuit and provides an improved calibration method using a multitone calibration signal. The apparatus automatically adjusts an electronic hybrid as part of a calibration procedure so as to eliminate undesirable echo effects when calls are placed along the line. The results of the balancing procedure are examined, and the values of the resistance and capacitance from the balanced ciruit are compared to determine whether the line is loaded or non-loaded. The electronic hybrid balancing process and echo cancellation circuitry may also be utilized in a circuit for converting four-wire communications systems to two-wire communications systems. The line conditioning device of the present invention utilizes a multitone signal to simulate the voice frequency spectrum between approximately 500 Hz and 3500 Hz to probe the line side with a plurality of tones (e.g.

Abstract: The present invention overcomes interface problems between proprietary handset ports on telephone base units and voice/data accessory products by allowing a user to automatically calibrate the telephone accessory product for an optimal interface match with the intended telephone base unit. This is accomplished through the use of a "Smart Interface Technology" (SIT) integrated chip set consisting of a full custom analog and semi-custom digital integrated circuit. The SIT incorporates three different methods for "learning " the characteristics of 4-wire port modular interfaces found in all telephone station sets. Basically, these methods determine the appropriate 4-wire terminal configurations, the transmit and receive channels of the intended telephone base unit, and adjust the channel sensitivities until an optimal and clear signal is provided for the user.

Abstract: An adaptive balance filter includes a transmission path, a reception path, and an adaptive filter having a signal output, a coefficient output for outputting filter coefficients, an error signal input, and a signal input coupled to the transmission path. There is a main filter which has a signal output, a signal input coupled to the transmission path, and a coefficient input terminal. There is also a first subtractor which has one input coupled to the reception path, another input coupled to the signal output of the main filter, and an output forming a further course of the reception path. A second subtractor has one input coupled to the reception path, another input coupled to the signal output of the adaptive filter, and an output coupled to the error signal input of the adaptive filter.

Abstract: A method and system for remotely calibrating a headset telephone with a reliable, accurate and easy to use user interface is provided. This method makes use of the remote programmability of advanced telephone headsets and DTMF signal encoding and permits the customer-user to instigate the calibration procedure with an ordinary telephone call. The invention provides the means by which the optimum settings can be transmitted to the headset, loaded and stored in the headset, thereby improving the audio quality of telephone headsets by providing adjustment steps for such audio qualities as microphone gain (transmit level), speaker gain, background noise and echo cancellation, filter functions and diagnostics. This method also provides audio feedback to a customer service representative performing the calibration to insure that the commands and adjustments were properly received.

Abstract: A transceiver circuit for use in a high speed data transmission network is disclosed that provides for simultaneous bidirectional transmission of data over coaxial or twisted pair media for replacing fiber optic cables. A transmitter circuit provides and output data signal to a bridge network. The bridge network develops a cancelling signal and a combined signal. A receiver section includes a high speed subtracting circuit that determines the difference between the cancelling signal and the combined signal to effectively cancel data supplied by the transmitter section.

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.