Abstract: The invention relates to a distribution frame device (1) for communications and data technology for switching over at least one electrical subscriber line (2) from a first service to a second service, wherein the distribution frame device (1) has a connection technology (3) for the electrical subscriber lines (2), a connection technology (4) for the electrical lines (5) of the first service and a connection technology (6) for optical fibres of the second service, wherein the distribution frame device (1) further has an active technology with at least one converter (14) for converting optical signals into electrical signals and vice versa for the second service, wherein a connection for optical fibres and a connection for electrical lines are associated with the at least one converter (14), wherein the distribution frame device (1) has means by means of which the connection technology (3) of the subscribers can selectively be connected to the connection technology (4) of the first service or to the associated

Abstract: The invention relates to a distribution frame device (1) for communications and data technology for switching over at least one electrical subscriber line (2) from a first service to a second service, wherein the distribution frame device (1) has a connection technology (3) for the electrical subscriber lines (2), a connection technology (4) for the electrical lines (5) of the first service and a connection technology (6) for optical fibers of the second service, wherein the distribution frame device (1) further has an active technology with at least one converter (14) for converting optical signals into electrical signals and vice versa for the second service, wherein a connection for optical fibers and a connection for electrical lines are associated with the at least one converter (14), wherein the distribution frame device (1) has means by means of which the connection technology (3) of the subscribers can selectively be connected to the connection technology (4) of the first service or to the associated

Abstract: A powered device is electronically connected to power sourcing equipment (PSE), to receive voltage signals from the PSE. The powered device comprises a rectifier unit, a recognition unit, a control unit, a converter and a powered circuit. The recognition unit identifies that the PSE is an Ethernet PSE or a DC PSE. The control unit controls whether the control unit output a negative voltage signal output by the rectifier unit, according to a positive voltage signal output by the rectifier unit and a identified result output by the recognition unit. The converter converts the negative voltage signal and the positive voltage signal to a working voltage of the powered circuit, to drive the powered circuit. To feed power by a single interface and identify that the PSE is the Ethernet PSE or the DC PSE, according to a simple circuit architecture.

Abstract: Communication devices coupled via a communication link may comprise physical layer devices that may be operable to determine presence of a received signal and to mitigate noise in the signal prior to processing and/or validating the signal. Analog and/or digital signal processing may be utilized to process the signal and/or mitigate noise in the signal. Noise mitigation may comprise near-end crosstalk cancelling and/or echo cancelling and/or may utilize local transmit signal information. Subsequent to noise mitigation, samples of the noise reduced signal may be accumulated and/or an average signal strength and/or average signal power level may be determined. The average signal strength and/or average signal power level may be compared to one or more thresholds which may be configurable and/or programmable.

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 adaptive hybrid system is coupled to a loop for adjusting trans-hybrid loss. The system comprises a fixed portion comprising a first receiver transfer function block and a first hybrid transfer function block. The fixed portion is configured to receive a far-end signal and mitigate frequency dependent attenuation experienced by the far-end signal. The system also comprises a variable portion comprising a second receiver transfer function block and a second hybrid transfer function block configured to subtract a transmit echo from the received far-end signal.

Abstract: In order to provide unbalanced ringing when an exchange line card provides a balanced ringing output the interface provides a ringing detector in circuit with a customer pair. On detecting balanced ringing signals from the line card, the interface takes over the customer line pair and provides unbalanced ringing signals to the customer and monitors for customer answer. By inserting the interface in circuit at the main distribution frame of an exchange, legacy customer premises equipment which is unable to respond to balanced signalling can be provided with an appropriate ringing signal without the necessity to provide differing line cards at the exchange.

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: Configurable analog input circuits are provided. An analog input circuit may include a plurality of configurable input channels, at least one analog-to-digital converter, and at least one processor. Each input channel may include a plurality of switches utilized to select a type of input signal received via the input channel and a set of input terminals selectively utilized to correspond with the selected type of input signal. The at least one analog-to-digital converter may be configured to convert, for each of the plurality of input channels, the selected type of input signal into a digital output. The at least one processor may be configured to control operation of the plurality of switches associated with each of the plurality of configurable input channels.

Abstract: A driver circuit for driving a transmit signal for a line includes a signal amplifier configured to deliver a transmit signal, present at a signal input of the signal amplifier, amplified with a gain to a signal output, a line interface circuit connected between the signal output of the signal amplifier and the line, and a hybrid circuit connected to the line interface circuit, the hybrid circuit configured to suppress the transmit signal and couple a received signal received via the line to a signal input of the signal amplifier to provide impedance synthesis.

Abstract: A method and apparatus provide an IP telephone or similar device with a mechanism to receive and at least briefly loop back discovery signals received from a telecommunications device such as an Ethernet switch while not permitting the loop back of data packet signals. No mechanical relays are required and the circuitry can be fully integrated on an integrated circuit using commonly available techniques, if desired.

Abstract: Driver circuit for driving a transmit signal for a line comprising a signal amplifier which delivers a transmit signal, present at a signal input of the signal amplifier, amplified with a gain to a signal output, a line interface circuit which is connected between the signal output of the signal amplifier and the line, and comprising a hybrid circuit which is connected to the line interface circuit, wherein the hybrid circuit suppresses the transmit signal and couples a received signal received via the line to a signal input of the signal amplifier for the purpose of impedance synthesis.

Abstract: A hybrid circuit for a full-duplex transceiver includes a two-to-four wire ratio converter (50, Z1, Z2) for forwarding a transmitted signal TX? on a transmission line (41) in response to an input signal TX. The ratio converter also produces a signal RXA in response to a received signal RX arriving on the transmission line, wherein signal RXA includes an echo of input signal TX. A passive filter (H1) and a first active filter (H2) each filter input signal TX to generate signals TXA and TXB summed with the RXA signal to form a signal RXB at the input of an amplifier (52, Z3, Z4) producing an output signal RXC. A second active filter (H3) filters input signal TX to generate a signal TXC summed with the RXC signal to produce the output signal RX. The impedance of the passive filter is designed so that when the transmission line has a target impedance, such as the impedance of an ideal twisted pair, the TXA output signal of the passive filter adequately offsets the TX signal echo in RXA.

Abstract: Embodiments of the invention relate generally to a configurable analog input channel with galvanic isolation. In one embodiment, the invention provides a configurable input channel for selectively receiving one of a plurality of different analog sensor inputs. The input channel includes an interface for implementing switch settings for a selected type of input signal; a set of input terminals, wherein at least two of the set of input terminals are selectively utilized to correspond with the selected type of input signal; an analog-to-digital converter for converting the input signal into a digital output, wherein an operation of the analog-to-digital converter is determined based on the switch settings; and an isolation barrier for isolating the configurable input channel.

Abstract: A telephone interface circuit comprises a first transistor for controlling opening and closing between a speech circuit and subscriber lines, a second transistor for controlling the first transistor to turn on and off, a positive feedback circuit connecting a collector terminal of the first transistor and a base terminal of the second transistor, an overcurrent detection circuit detecting overcurrent applied to the subscriber lines, and a breaker circuit for turning off the first transistor by lowering the base potential of the second transistor to a low potential when overcurrent is detected at the overcurrent detection circuit. Here, the base terminal of the first transistor and a collector terminal of the second transistor are connected. Further, when off-hook, the base potential of the second transistor is controlled in such a manner as to become a high potential by a microcomputer.

Abstract: A midspan power adapter is provided for use in a balanced communication system, such as an Ethernet system, where differential signals are transmitted between two devices. The adapter passes data signals through, and provides power to an end device, such as an IP phone, with significantly less contribution to the electromagnetic emissions of the system than known midspan adapters. Balance and symmetry inherent in a structured cable can be maintained by a termination network connecting center taps of a transformer and the spare pairs of both the incoming and outgoing cables to a common point. The adapter can provide power through unused wires (known as spare pair power) or by combining power with data signals (known as phantom feed). A common mode choke is included in the power feed to prevent noise currents from flowing through the power supply connections to earth ground, helping to minimize radiated noise.

Abstract: An apparatus and method for enabling Cisco legacy power to support IEEE 802.3af standard power. A network power system capable of delivering data terminal equipment power via a media dependent interface (MDI) includes power source equipment according to a first power via MDI scheme such as Cisco legacy power and at least one powered device according to a second power via MDI scheme such as IEEE standard power. A power compatibility module is inserted between the power source equipment and the powered device to enable the power source equipment to appear according to the first power via MDI scheme and the powered device to appear according the second power via MDI scheme. In one embodiment, the module includes switches, a DC/DC converter, an IEEE power source equipment circuit, and an isolator. The module may optionally include a user signaling device for communicating operating conditions of the module to a user.

Abstract: A method and apparatus provide an IP telephone or similar device with a mechanism to receive and at least briefly loop back discovery signals received from a telecommunications device such as an Ethernet switch while not permitting the loop back of data packet signals. No mechanical relays are required and the circuitry can be fully integrated on an integrated circuit using commonly available techniques, if desired.

Abstract: A method and apparatus provide an IP telephone or similar device with a mechanism to receive and at least briefly loop back discovery signals received from a telecommunications device such as an Ethernet switch while not permitting the loop back of data packet signals. No mechanical relays are required and the circuitry can be fully integrated on an integrated circuit using commonly available techniques, if desired.

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: The invention relates to a method and a circuit for adapting the impedance in a telecommunication connection comprising a speech path and a data path having modems. Conductive properties measured by the modems are used to precisely adjust the impedance on the speech path.

Abstract: A monolithic transceiver integrated circuit that includes a substrate, a transmitter subsystem of one or more subcircuits on the substrate, and a receiver subsystem of one or more subcircuits on the substrate. Also included is a bias current supply coupled to the receiver and transmitter subsystems to provide bias current. The bias current supply includes a first bias circuit on the substrate coupled to, and to supply bias current to, a first subcircuit of the transmitter subsystem. The first bias circuit includes a first current modulator having a first switch input to indicate that the bias current is to start or stop being supplied to the first subcircuit. The first current modulator is to control the rate of change of supplied bias current in response to the first switch input. The first subcircuit may be a power amplifier. The control of the rate of change reduces oscillator pull in at least one oscillator included in the integrated circuit.

Abstract: One aspect of the invention relates to a method for line matching of analog communication lines in telecommunications networks, whereby signal processor(s) and/or programmable digital filters are used. Coefficients of the line transmission function are calculated by an echo compensator to be compared with pre-specified filter coefficients in a filter device assigned to the line, in which case, an incorrect line matching is identified and a new set of filter coefficients is generated, which is fed into the filter device. In this case, the first values to be accepted and processed for the coefficients of the line transmission function calculated by the echo compensator and used for comparison, are those that are determined by an echo compensator for a first line gateway in a line path, which is associated with the reflection with the shortest delay time. In networks with high dispersion of the line parameters, the invention re-establishes the task distribution between line matching and echo compensator.

Abstract: A device comprises a termination impedance circuit, coupled to a communication link. The termination impedance circuit provides a termination impedance of the device, wherein the impedance is selectable. A second device comprises an echo-cancel hybrid circuit, coupled to a communication link, that provides an echo cancel characteristic, wherein the characteristic is selectable.

Abstract: Methods and apparatus for protecting quality of service during a process involving bridge tap in a communications system are described. Bridge tap may occur during system construction, central office re-concentration, replacement projects, upgrade projects, expansion projects, and installation of back-up cables, etc. Cables, with one end connected to a point in the system, and the other end left unterminated, result in bridge tap. In the bridge tap moderator of the present invention, a plurality of termination networks are attached to a modular connector such that a separate termination load is placed across each connector terminal pair for each corresponding wire pair of the cable. Communication lines can be easily attached to the moderator thereby easily, quickly, and efficiently eliminating bridge tap on a large number of wire pairs. The bridge tap modulator apparatus and method of use also minimize the amount of time bridge tap exists during cable and/or communication device installation.

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 digital transmission line tap circuit is provided for applying a non-intrusive tap on a digital transmission line thus allowing the transmission signal to be monitored or utilized by another piece of transmission equipment. The tap circuit incorporates all the required functions of the tap in one circuit and eliminates large components, such as termination transformers.

Abstract: A method and apparatus for enabling multiple protocol communication over a network are disclosed. A first circuit communicates first signals in a first frequency band using a first data protocol and attenuates second signals in a second frequency band using a second data protocol. The first data protocol supports a first modulation technique and a second modulation technique. A second circuit communicates the second signals in the second frequency band using the second data protocol.

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 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 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: In one aspect of the invention a communication device including circuitry operable to facilitate dynamic impedance matching includes an image impedance operable to be coupled to a receiver/transmitter pair associated with a line impedance. The device also includes matching circuitry coupled to the line impedance and the image impedance, the matching circuitry operable to measure an impedance mismatch between the line impedance and the image impedance and to generate a control signal based on the measured impedance mismatch. The image impedance is operable to be varied to more closely match the line impedance based at least in part on the control signal.

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. 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. A Universal Serial Bus (USB) plug may be provided to receive a bias voltage from the PC for biasing circuits of the cordless telephone system through the interface adapter. Advantageously, the preferred interface adapter utilizes 100% passive components for a low-cost yet effective means to provide mobility for an end user during voice communications over the Internet.

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 system for matching impedance in the circuitry of an xDSL communication device to improve noise cancellation resulting from signal leakage between transmit and receive signals. The system for matching impedance includes a transformer configured to couple an impedance, which is substantially equal to a line impedance, to a line coupling transformer, and is applicable to all known hybrid topologies. The transformer is ideally as closely matched to the line coupling transformer as possible. This technique allows greatly improved impedance matching in the hybrid, which directly benefits the performance of xDSL communication devices.

Abstract: A high bandwidth telephone line transceiver for connecting telecommunications equipment to a telephone line provides a pair of isolation capacitors connected to the telephone line to transmit the telephone signals across the requisite electrical isolation barrier. The capacitors are connected to a user-side hybrid circuit that provides a line impedance match for the telephone circuit, and converts the two wire connection to the capacitors to a 4 wire circuit for separate transmit and receive signal paths. The receive signal path extends through a signal op amp to a high pass filter that transmits the DSL download bandwidth and rejects the upload bandwidth and voice spectrum. The received signal is then fed to an analog/digital converter, and the digitized signal is connected to a DSP. The DSP is connected to a data handling device via a USB port, a PCI interface, or the like. The transmit signal path extends from the DSP circuit to a transmit path digital/analog converter.

Abstract: A current sense circuit for sensing a current in a subscriber loop comprising a transformer having a first and second winding coupled for sensing a differential current in a loop, a sense winding for producing a sense current in response to a magnetic flux induced in the transformer due to the differential current, an amplifier circuit for receiving the sense current and wherein the sense current is indicative of a signal on the loop, and the amplifier being configured such that a transformer introduces a low insertion loss at a frequency of operation of the loop.

Abstract: An adaptive transmission line impedance matching device and method are disclosed. The device and method can be used, for example, in xDSL and home phone line network applications. The adaptive impedance matching device comprises a signal transmission section, a signal receiving section, a variable impedance matching network and a signal analysis section. The signal receiving section is operable to receive signal information transmitted across a transmission line. The signal analysis section is then operable to calculate a proper impedance match based upon the signal information and to adjust the variable impedance matching network according to the calculated impedance match. The device and method are robust enough, for example, to account for dynamic mismatches when telephone sets are taken off-hook during digital (e.g., xDSL) network operation.

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: 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: 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 monolithic transceiver integrated circuit that includes a substrate, a transmitter subsystem of one or more subcircuits on the substrate, and a receiver subsystem of one or more, subcircuits on the substrate. Also included is a bias current supply coupled to the receiver and transmitter subsystems to provide bias current. The bias current supply includes a first bias circuit on the substrate coupled to, and to supply bias current to, a first subcircuit of the transmitter subsystem. The first bias circuit includes a first current modulator having a first switch input to indicate that the bias current is to start or stop being supplied to the first subcircuit. The first current modulator is to control the rate of change of supplied bias current in response to the first switch input. The first subcircuit may be a power amplifier. The control of the rate of change reduces oscillator pull in at least one oscillator included in the integrated circuit.

Abstract: A circuit provides a modulation signal to an input terminal of a line modulator which places a line current modulated in accordance with the modulation signal on a telephone line. An amplifier of the circuit amplifies an analog input signal to provide the modulation signal at an output terminal. A first resistor and a first capacitor are coupled in series between a first input terminal of the amplifier and the line, and a second resistor and a second capacitor are coupled in series between a second input terminal of the amplifier and the line. First and second precharge amplifiers are used to precharge the first and second capacitors, respectively, to reduce DC setup time.

Abstract: A system and method of powering a fiber optic communication network are provided which transmits communication data between a telephone company central office and remote user device. The system includes a power source configured to provide an electrical supply voltage to a digital subscriber line access multiplexer. The power source having an AC power feed for providing power to the digital subscriber line access multiplexer and a DC power feed for providing power to the digital subscriber line access multiplexer when the AC power feed is not supplying power. Further, an electrical conducting medium configured to conduct the electrical supply voltage and the communication data from the digital subscriber line access multiplexer to the remote user device is provided.

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 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 ringer impedance for a variety of international phone standards while also providing a proper isolation barrier to the phone line is disclosed. More particularly, a DAA circuitry may be utilized which satisfies many or all ringer impedance standards without the use of additional discrete impedance devices. The ringer impedance standards may be satisfied by use of an impedance structure coupled between the TIP and RING lines and actively controlling the current drawn through the hookswitch devices when a ringing event is detected so as to control the impedance seen at the TIP and RING lines during a ringing event. The detection of the ringing event may be performed on the phone line side of an isolation barrier.

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: 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.