Abstract: Embodiments of methods and systems for operating a communications device that communicates via inductive coupling are described. In an embodiment, a method for operating a communications device that communicates via inductive coupling involves detecting a system condition associated with the communications device and tuning a matching network of the communications device in response to the system condition, where the matching network includes a hybrid transformer that separates a receiver of the communications device from a transmitter of the communications device. Other embodiments are also described.

Abstract: An amplifier is provided that includes a differential pair of transistors configured to steer a tail current responsive to a differential input voltage. The amplifier also includes a transconductor that tranconducts high-frequency changes in the differential output voltage into a differential bias current conducted through the differential pair of transistors.

Abstract: An integrated hybrid circuit includes a transmission unit, a transceiver coil, a transceiver circuit, a hybrid matching circuit, and a receiving circuit. The transmission unit generates a pair of upstream signals according to a user transmission signal. The transceiver coil transmits the pair of upstream signals to a central office through a pair of twisted pair, and receiving a pair of downstream signals from the central office through the pair of twisted pair. The hybrid matching circuit receives an adjustment signal to adjust selective impedances. The receiving circuit receives the pair of downstream signals from the central office, and generates the adjustment signal according to downstream and upstream rates and signals from the hybrid matching circuit. The transmission unit adjusts transmission power and bandwidth of the transmission unit and the receiving unit adjusts filter bandwidth of the receiving unit according to the adjustment signal for optimizing upstream and downstream rates.

Abstract: A circuit for the analog correlation of a signal to remove impairments such as echo, cross talk and intersymbol interference is described. A duplexing circuit which improves echo response by providing a second transformer is described.

Abstract: In a line driver/receiver circuit where the line driver is connected with its output terminals to a load for supplying a transmit signal thereto and where the receiver is connected with its input terminals to the load for simultaneously receiving a receive signal therefrom, the transmit signal on the input terminals of the receiver is canceled by connecting the output terminals of the line driver to the load via equal complex sense impedances of an impedance value that is much smaller than the impedance value of the load impedance to match the load impedance, connecting the input terminals of the receiver to the load via equal first resistors and to respective output terminal of the line driver via equal second resistors, and providing transconductance amplifiers to sense the voltage across the sense impedances and supply corresponding currents to respective input terminal of the line driver.

Abstract: Systems, methods, and other embodiments associated with echo cancellation are described. According to one embodiment, a method uses two signals from a transmitter as input to a look-up table to generate a non-linear echo cancellation signal. The non-linear echo cancellation signal is applied to a receiving path to reduce non-linear echo distortion on the receiving path based at least in part on the current signal and the previous signal.

Abstract: A reach back secure communications terminal includes a digital PBX adapter that offers immediate and secure voice, data and video connectivity over any of various commercially available PBX systems. In addition to use with a PBX system, integrated components simplify access to varied networks allowing deployed users to select and connect quickly to a network that best supports their present mission. Commercial or optional NSA Type 1 encryption may be implemented. Networking options include any of PSTN, PBX, GSM (or CDMA or other cell telephone standard), SAT, IP and WiFi. The digital PBX adapter includes an audio mixer that converts a 4-wire input from a handset jack of a PBX handset base, into a 2-wire output destined for an encryption unit (FNBDT). The user determines a necessary gain of the audio mixer for the particular PBX system by trial and error using a multi-position switch.

Abstract: Sound quality is enhanced in a sound system including handsets and headsets. Handset sound enhancing algorithms are implemented in a handset. The handset automatically determines which, if any, of a plurality of headset sound enhancing algorithms are active in a headset in communication with the handset. The handset determines how to use the handset sound enhancing algorithms in a sound processing channel based on which of the headset sound enhancing algorithms are active in the headset.

Abstract: Systems and methods for operating a telecommunications device in whisper mode are presented. The method generally includes adjusting a transmit audio signal gain responsive to a transmit audio signal voice activity status, transmit audio signal speech level, transmit audio signal signal-to-noise ratio, and receive audio signal voice activity status. A sidetone feedback signal gain is adjusted in conjunction with adjusting the transmit audio signal gain.

Abstract: Sound quality is enhanced in a sound system including handsets and headsets. Handset sound enhancing algorithms are implemented in a handset. The handset automatically determines which, if any, of a plurality of headset sound enhancing algorithms are active in a headset in communication with the handset. The handset determines how to use the handset sound enhancing algorithms in a sound processing channel based on which of the headset sound enhancing algorithms are active in the headset.

Abstract: Sound quality is enhanced in a sound system including handsets and headsets. Handset sound enhancing algorithms are implemented in a handset. The handset automatically determines which, if any, of a plurality of headset sound enhancing algorithms are active in a headset in communication with the handset. The handset determines how to use the handset sound enhancing algorithms in a sound processing channel based on which of the headset sound enhancing algorithms are active in the headset.

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: In a communication machine room wideband noise suppression system, a sensing unit detects a noise source produced by a fan during the operation thereof and generates a noise input signal and a feedback signal, which are sent to a signal amplifying unit for signal amplification. The amplified signals are then sent to a signal converting unit and converted into digital signals. A multi-channel hybrid controller receives the digital signals and makes corrections and conduct rapid convergence algorithm to derive a reverse digital signal, which is sent to the signal converting unit and converted into a reverse analog signal. The reverse analog signal is sent to the signal amplifying unit for power amplification to generate a control signal for driving a loudspeaker unit to produce interfering acoustic wave, so as to cancel out the noise source and achieve the purpose of eliminating wideband noise.

Abstract: Sound quality is enhanced in a sound system including handsets and headsets. Handset sound enhancing algorithms are implemented in a handset. The handset automatically determines which, if any, of a plurality of headset sound enhancing algorithms are active in a headset in communication with the handset. The handset determines how to use the handset sound enhancing algorithms in a sound processing channel based on which of the headset sound enhancing algorithms are active in the headset.

Abstract: In a line driver/receiver circuit where the line driver is connected with its output terminals to a load for supplying a transmit signal thereto and where the receiver is connected with its input terminals to the load for simultaneously receiving a receive signal therefrom, the transmit signal on the input terminals of the receiver is canceled by connecting the output terminals of the line driver to the load via equal complex sense impedances of an impedance value that is much smaller than the impedance value of the load impedance to match the load impedance, connecting the input terminals of the receiver to the load via equal first resistors and to respective output terminal of the line driver via equal second resistors, and providing transconductance amplifiers to sense the voltage across the sense impedances and supply corresponding currents to respective input terminal of the line driver.

Abstract: A system and method are provided for detecting acoustic echo in a telecommunications transmission. Detected acoustic echo is analyzed to determine if the acoustic echo includes characteristics indicative of use of a speakerphone by a remote party. Specific characteristics analyzed include the presence of multiple bulk delay values, echo magnitude, and the length of time for echo delays present within the telecommunications system. If the detected acoustic echo falls outside the range of acceptable parameters, or otherwise exceeds threshold limits, a warning signal is transmitted to the user indicating a high likelihood that the remote party is using a speakerphone. Warning the user of speakerphone use by the remote party can be helpful in ensuring that the communications between the parties is maintained in confidence.

Abstract: A transceiver for a transmission and reception signal which can be transmitted via a signal line having a particular line impedance (ZLINE), having a line driver (6) for driving a transmission signal via the signal line and having an analog echo cancellation filter (15) for signal suppression for an echo signal brought about by the transmission signal, where the line driver (6) has a synthesized output impedance (RSYN), with the line driver (6) having a downstream hybrid circuit (11) for connecting an analog echo cancellation filter (15).

Abstract: A modem includes a base unit for transmitting a data signal, and a communication card which receives the data signal from the base unit over a wireless medium and which performs echo canceling on the data signal. The base unit is in communication with a telephone line and receives an original signal from the telephone line. The base unit generates an RF modulated signal based on the original signal. The base unit includes a transmitter for transmitting the data signal. Circuitry in the base unit receives the original signal from the telephone line and generates a combined data signal from the original signal and echo signals and maintains a peak voltage of the combined signal which is within the linear amplification region of the transmitter.

Abstract: A hybrid with a plurality of selectable hybrid input paths each having an associated hybrid input path filter is provided. The hybrid includes a plurality of selectable receive paths each having an associated receive path filter. The hybrid further includes a hybrid output. The selection of any filter is non-mutually exclusive to the concurrent selection of another filter.

Abstract: An improved data access arrangement device for use in full-duplex two-wire communication systems having a transmission impedance characteristic. The DAA includes a transmit amplifier and a receive amplifier adapted for connection to a two-wire line, a codec connected to the transmit amplifier for generating a transmit signal, a summation device connected to the receive amplifier, an echo cancellation path including a variable gain amplifier, where the path extends between the codec and the summation device, and wherein the variable gain amplifier is adjusted in accordance with the transmission impedance characteristic. The variable gain amplifier may include a gain register that is programmed by a microprocessor, or may have the gain set by user-configurable switches. The summation device is preferably an operational amplifier.

Abstract: A digital telephone answering device having speakerphone capability allows a recorded message to be played back and heard by the far-end party as well as over the local speakerphone by the near-end party during speakerphone operation as if it were a normal receive signal. Moreover, normal speakerphone conversation is possible during this conversational playback mode allowing the far-end party and/or near-end party to break-in over the played back pre-recorded message as desired and be heard by the other party. Both message and conversation signals are preferably (but not necessarily) at similar levels. Also, the message playback at the near end is preferably (but not necessarily) subject to the same speakerphone digital volume control as that received at the far end.

Abstract: The present invention provides an echo reduction apparatus, system, and method that advantageously reduces echo when communicating over packet-switched networks. An echo reduction apparatus, including echo reduction circuit, operably couples a headset or handset device to an audio source that is capable of transmitting a sound signal. The echo reduction circuit receives the sound signal from the audio source and a transmit signal from the headset or handset device and provides an adjusted sound signal to the audio source. Advantageously, a variety of headsets and handsets may be used in accordance with the present invention with reduced caller echo and without the need to purchase new headsets or handsets.

Abstract: A line interface performs echo cancellation without the use of a hybrid filter network and includes a transmit path having a line driver, a single matching network terminating the line, and a single transformer. The transformer uses split windings on both the primary side and the secondary (line) side. Each half of the primary side is tapped to obtain a turns ratio of N1:N2, while each half of the secondary side of the transformer has N windings. The single matching impedance is coupled in parallel between the first winding and the second winding on each half of the primary side. Either the voltage across the matching impedance or the voltage across the receive terminals is bootstrapped to the receive signal through multiple negative feedbacks. The transfer function of the line driver is shaped as a first-order high-pass filter (HPF) to reject any out-of-band noise and distortion components.

Abstract: A hybrid circuit that couples a broadband modem to a POTS or ISDN telecommunication line (TL) and includes a transformer bridge circuit (TBC) that includes a bridge circuit (BC). The bridge circuit includes four legs formed by impedance matching networks and parts of the transformer, and a differential drive amplifier (DRV) that performs impedance synthesis. A secondary winding (TS) of the transformer is magnetically coupled to the first and the second primary windings and is electrically coupled to the telecommunication line. First and second impedance dividers (Zhin1, Zhout1 and Zhin2, Zhout2) are connected to the various nodes to provide outputs to a receive amplifier (RCV). The impedance matching networks (Zm1; Zm2) include various passive and reactive components that together provide an impedance value selected based upon the line impedance reflected into the primary windings (TP1; TP2) of the transformer.

Abstract: A directional coupler for a modem has a high common mode noise rejection characteristic with low transmit signal leakage, and reduced distortion of components mixed with a received signal. A primary filter network is connected to a communications circuit. The primary filter network has an output connected to an input of an amplifier. A feedback network is connected between the input and output of the amplifier. The primary filter network, the amplifier and the feedback network are arranged to provide a virtual ground at the input of the amplifier, and a filter characteristic which attenuates frequencies in the transmit signal band. The advantage is reduced component count while providing excellent transmit signal rejection and reducing received signal distortion.

Abstract: A method and apparatus is provided for performing an active impedance differential current feedback. A signal is received. A current feedback of an output signal in an active feedback synthesis mode is performed based upon the signal. The active current feedback includes using an active feedback network for conditioning an output signal, converting the signal into a differential current signal, and summing at least two components of the differential current signal for performing a differential feedback.

Abstract: A method of and apparatus for optimizing signal transformation from a twisted pair transmission line to a combination transmitter and receiver for a frame-based communications network, the transmitter having a transmit output pair port for transmitting signals onto the frame-based communications network over the twisted pair transmission line, the receiver having a receive input pair port for receiving signals from the frame-based communications network over the twisted pair transmission line. A transformer is coupled between the twisted pair transmission line and each of the transmit output pair port and the receive input pair port. The transformer has a coil across the twisted pair, a transmit coil across the transmit output pair port, and a receive coil across the receive input pair port. A transfer ratio between the transmit coil and the coil across the twisted pair is optimized for transmitting signals.

Abstract: The present invention provides an echo reduction apparatus, system, and method that advantageously reduces echo when communicating over packet-switched networks. An echo reduction apparatus, including echo reduction circuit, operably couples a headset or handset device to an audio source that is capable of transmitting a sound signal. The echo reduction circuit receives the sound signal from the audio source and a transmit signal from the headset or handset device and provides an adjusted sound signal to the audio source. Advantageously, a variety of headsets and handsets may be used in accordance with the present invention with reduced caller echo and without the need to purchase new headsets or handsets.

Abstract: An ADSL POTS splitter includes an enhanced low pass filter. The enhanced low pass filter includes a first filter capacitor, a first non-isolated inductor, a second non-isolated inductor, a first isolated inductor and a common mode choke. The second non-isolated inductor is connected to the first non-isolated inductor. A first winding of the second non-isolated inductor is connected in series with a first winding of the first non-isolated inductor. A second winding of the second non-isolated inductor connected in series with a second winding of the first non-isolated inductor. The first isolated inductor is connected to the first non-isolated inductor with a first winding of the first isolated inductor connected in series with the first winding of the first non-isolated inductor and to a first lead of the first filter capacitor. A second winding of the first isolated inductor connected in series with the second winding of the first non-isolated inductor and to a second lead of the first filter capacitor.

Abstract: Differential echo cancellation receiver circuitry with dynamic cancellation of excess DC output current. Differential input circuitry provides for cancellation of incoming DC voltage and the incoming transmit signal echo while passing the receive signal. Excess DC current appearing in the input circuitry as part of the incoming DC voltage and echo signal cancellation is shunted away from the output circuitry with dynamically biased current shunting circuitry that tracks changes in the DC current within the input circuitry.

Abstract: A hybrid matching system is disclosed for use with a transmitter and receiver. The hybrid matching system includes a pair of transmitter output nodes, a pair of receiver input nodes, and a pair of terminals for interfacing to a transmission line. The system further includes a first impedance bridge portion including at least one inductor for coupling to the transmission line terminals via at least one transformer winding, and a second impedance bridge portion interposed between the pair of transmitter output nodes and the first impedance bridge portion, and interposed between the pair of receiver input nodes and the first impedance bridge portion.

Abstract: An electronic circuit for connecting a standard analog telephone to the analog microphone and loudspeaker connections on a personal computer and for separating the talk signal from the combined talk/listen signal occurring at the telephone, effectively minimizing undesirable echo.

Abstract: A transceiver system is disclosed for use in a telecommunication system. The transceiver system includes a transmission circuit including a transmitter input coupled to an input of a transmission amplifier, a receiver circuit including a receiver output coupled to an output of a receiver amplifier, and a transmission line interface circuit that is coupled to an output of the transmission amplifier and to an input of the receiver amplifier. The transmission line interface circuit includes a matching impedance that is directly coupled to a feedback path of the transmission amplifier and that terminates the transmission line of the transceiver system.

Abstract: A line card and method is provided which supports symmetric and asymmetric telecommunication services, such as symmetric and asymmetric DSL services. The line card may support concomitantly POTS and asymmetric DSL services or support DSL services. A xDSL interface provides processing for DSL signals and a POTS interface provides processing for POTS signals. The line card is capable of switching operating modes or which services it is supporting. Preferably, the line card is capable of switching operating modes during a communication session. The line card may switch modes based on instructions received from external devices, such as CPE or far end equipment, based on preprogrammed software or based on operation of the line card.

Abstract: A hybrid circuit forming an interface between a transmission line and heads of transmission-reception of signals in bands of different frequencies in transmission and reception, including a line transformer, and means for separating bands combined with echo cancellation means.

Abstract: A system for data communication is disclosed that comprises a hybrid circuit (220) that receives a signal. A switched gain circuit (204) coupled to the hybrid circuit (220) receives the signal from the hybrid circuit (220). A receiver circuit (206) coupled to the switched gain circuit (204) receives the signal from the switched gain circuit (204). The switched gain circuit (204) adjusts the power of the signal transmitted to the receiver circuit (206). More specifically, the switched gain circuit (204) detects the power of the signal received from the hybrid circuit (220), and adjusts the power of the signal transmitted to the receiver circuit (206) based upon the power of the signal received from the hybrid circuit (220). A method for data communication is disclosed. A signal is received using a hybrid circuit (220). The signal is transmitted to a switched gain circuit (204) coupled to the hybrid circuit (220). The power of the signal is adjusted using the switched gain circuit (204).

Abstract: A hybrid matching system is disclosed for use with a transmitter and receiver. The hybrid matching system includes a pair of transmitter output nodes, a pair of receiver input nodes, and a pair of terminals for interfacing to a transmission line. The system further includes a first impedance bridge portion including at least one inductor for coupling to the transmission line terminals via at least one transformer winding, and a second impedance bridge portion interposed between the pair of transmitter output nodes and the first impedance bridge portion, and interposed between the pair of receiver input nodes and the first impedance bridge portion.

Abstract: A hybrid circuit that couples a broadband modem to a POTS or ISDN telecommunication line (TL) and comprises a transformer bridge circuit (TBC) that includes a bridge circuit (BC). The bridge circuit is constituted by four legs of which a first (A) and a second (B) nodes, that do not belong to a same leg, are connected to the two outputs of a differential drive amplifier (DRV) that performs impedance synthesis. A first leg is made of a first impedance matching network (Zm1) connected between the second node (B) and a third node (C). A second leg is made of a first primary winding (TP1) of a transformer and is connected between the third (C) and the first (A) nodes. A third leg is made of a second impedance matching network (Zm2) connected between the first node (A) and a fourth node (D). A forth leg is made of a second primary winding (TP2) of the transformer and is connected between the fourth (D) and second (B) nodes.

Abstract: The invention relates to the separation of narrowband and broadband services in a telecommunications network. Signals belonging to a narrowband service are transferred in a first frequency range below a given threshold frequency and signals belonging to a broadband service are transferred in a second frequency range above said threshold frequency in the transmission link. The transmission link utilizes a splitter element comprising a low-pass filter unit and a high-pass filter unit, signals relating to narrowband service being separated to their dedicated interface by the low-pass filter unit and signals relating to broadband service being separated to their dedicated interface by the high-pass filter unit. In order that high-quality service may be offered to subscribers by means of a splitter element as simple and cost-effective as possible, filtering is implemented in the low-pass filter unit by means of a bidirectional active filter (LPF′).

Abstract: A hybrid circuit models a plurality of attributes of a communication system including a subscriber line coupled to a line interface circuit. The plurality of attributes includes subscriber line impedance, and impedance of a coupling transformer. The attributes are based on other factors, such as whether or not bridge taps exist at or near the line interface circuit on the subscriber line. The plurality of attributes are modeled by a specific arrangement of resistive and capacitive elements to substantially duplicate the collective transformative effects of the attributes on a transmission signal being sent out on the subscriber line. The transmission signal is transformed and provided to an output, where it is subtracted from a composite signal representing a combination of the actual transformed transmission signal and a receive signal. The subtraction yields an isolated receive signal, which is later processed to recover the full receive signal.

Abstract: A directional coupler for a modem has a high common mode noise rejection characteristic with low transmit signal leakage, and reduced distortion of components mixed with a received signal. A primary filter network is connected to a communications circuit. The primary filter network has an output connected to an input of an amplifier. A feedback network is connected between the input and output of the amplifier. The primary filter network, the amplifier and the feedback network are arranged to provide a virtual ground at the input of the amplifier, and a filter characteristic which attenuates frequencies in the transmit signal band. The advantage is reduced component count while providing excellent transmit signal rejection and reducing received signal distortion.

Abstract: A current sensing circuit (50) for use in an ADSL interface circuit senses an input current (IL) flowing through a resistor (R1) and provides an image output signal at an output which is an image of the input current.

Abstract: The Least Mean Square (LMS) and Normalized LMS (NLMS) algorithms commonly employed in adaptive filters of echo cancelers are further optimized. Finite impulse response (FIR) filters are used to estimate a transfer function of an echo channel in a communications link. The LMS and NLMS algorithms are used to adapt the filter coefficients of the estimated transfer functions. By including the echo channel energy gain in the LMS or NLMS update equation, adaptation speed is increased by making adaptation responsive to the channel energy gain. An algorithm for estimating the echo channel energy gain adapts the estimate based on measured system parameters, such as a measured instantaneous channel gain and a near-end voice level. By considering in the NLMS algorithm, the average energy of either the microphone signal or the error signal, as well as the standard reference signal, a higher nominal update gain can be used. With a higher nominal update gain, the NLMS algorithm will converge more quickly.

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: Full duplex circuits provide a bi-directional signal path at one port for transmit and receive signals and also provide separation between the transmit and receive signals at their respective ports. To accomplish this, the circuits employ amplifiers arranged in either a bilateral T hybrid or balanced impedance configuration. One application is in a transducer interface, where a single transducer is used as both a speaker/ear phone and a microphone. Another application is in a telephone line interconnect, where the telephone line interface simultaneously transmits and receives electrical signals representing audio data, e.g., voice data. The transducer interface drives a receive signal onto a transducer to create audio output while simultaneously generating a transmit signal from audio input. The telephone line interconnect drives a transmit signal through a transformer to send the transmit signal to a telephone line while simultaneously transferring a receive signal from the telephone line.

Abstract: A system for data communication is disclosed that comprises a hybrid circuit (220) that receives a signal. A switched gain circuit (204) coupled to the hybrid circuit (220) receives the signal from the hybrid circuit (220). A receiver circuit (206) coupled to the switched gain circuit (204) receives the signal from the switched gain circuit (204). The switched gain circuit (204) adjusts the power of the signal transmitted to the receiver circuit (206). More specifically, the switched gain circuit (204) detects the power of the signal received from the hybrid circuit (220), and adjusts the power of the signal transmitted to the receiver circuit (206) based upon the power of the signal received from the hybrid circuit (220). A method for data communication is disclosed. A signal is received using a hybrid circuit (220). The signal is transmitted to a switched gain circuit (204) coupled to the hybrid circuit (220). The power of the signal is adjusted using the switched gain circuit (204).