Abstract: A first device and a second device may coordinate to determine a power level or frequency in a first frequency band that is associated with causing intermodulation (IM) interference at a second frequency band (e.g., a protected frequency band). An IM interference detection test may include at least a first test signal transmitted from the first device to the second device via a communications medium. The second device may detect for the presence of IM interference associated with the first test signal. A series of test signals may be used to identify power levels and/or frequencies that cause IM interference in the second frequency band. A transmitting device may improve performance by increasing power for particular frequencies up to a power level that maintains IM interference below a threshold level.

Abstract: An apparatus which accepts a connection of an external telephone and connects to a telephone line includes a first controller configured to control line impedance via the telephone line, a detecting unit configured to detect a ringing signal received from the telephone line, a determining unit configured to determine whether the external telephone captures a telephone line, and a second controller configured to invalidate the control over line impedance by the first controller in a case where the apparatus is a standby state and validate the suppression of the control over ringer impedance by the first controller in a case where the detecting unit detects the ringing signal and the determining unit determines that the external telephone does not capture a telephone line.

Abstract: A telephone on-hook/off-hook state communication system. The system includes a first part, for example in the form of an In-Line Analog POTS presentation Adapter, which is operable to interconnect between a telephone apparatus and a pair of conductors, and a second part operable to interconnect between the pair of conductors and a telephone adapter unit, the first part including a variable impedance and means for changing the impedance of the variable impedance such that a property of the impedance at a predetermined frequency (f) greater than zero changes in response to the telephone apparatus transitioning between an on-hook state and an off-hook state, the second part including a detector for detecting the change in the impedance of the variable impedance of the first part via the pair of conductors.

Abstract: A test system for diagnosing twisted pair wiring includes a system processor in communication with a subscriber line interface module, which includes a codec and a SLIC (Subscriber Line Interface Circuit). The SLIC transmits a waveform having a frequency used for voice or baseband modem transmissions onto the twisted pair wiring. The system processor transmits a digital PCM (Pulse Code Modulation) stream to the codec, and the codec converts the digital PCM stream into the waveform transmitted onto the twisted pair wiring. In response to the transmitted waveform, the SLIC senses current on the twisted pair wiring. The codec generates an output waveform corresponding to the sensed current. The system processor receives the output waveform from the codec as a digital PCM stream, synchronizes the transmitted waveform and the output waveform at a single sample, and determines electrical properties of the twisted pair wiring from the output waveform.

Abstract: A method is proposed for calculating a line performance, or stability, measure for a telephone line. Various physical parameters associated with the line, such as insulation resistance, capacitance and DC voltages, are measured. The values for each of the parameters are compared to expected values, which are based on historical values measured for that line. Individual performance measures for each parameter are calculated based on the difference between the actual and expected values, normalised by the deviation of that parameter. The deviation accounts for general fluctuations across all the lines. A weighting value is also applied, based on knowledge of values relevant to the good operation of lines. The deviation effectively gives a scaling, and the weighting gives a context to the measured values for a single line. The individual performance measures are summed to get the final performance measure for the line.

Abstract: A telephone on-hook/off-hook state communication system. The system includes a first part, for example in the form of an In-Line Analog POTS presentation Adapter, which is operable to interconnect between a telephone apparatus and a pair of conductors, and a second part operable to interconnect between the pair of conductors and a telephone adapter unit, the first part including a variable impedance and means for changing the impedance of the variable impedance such that a property of the impedance at a predetermined frequency (f) greater than zero changes in response to the telephone apparatus transitioning between an on-hook state and an off-hook state, the second part including a detector for detecting the change in the impedance of the variable impedance of the first part via the pair of conductors.

Abstract: The present invention discloses circuits for isolating and attenuating signals generated by a telephone network. In disclosed embodiments, a metering pulse signal is isolated from the terminals of the connecting device, and then attenuated with an impedance that is synthesized with a programmable digital signal processor. Embodiments also utilize the digital signal processor to synthesize a termination impedance for the connecting device. The termination impedance matches closely the characteristic impedance of the network, so as to minimize wave reflections and the like.

Abstract: The present invention concerns methods for estimating one or more transmission properties of a telecommunications transmission line. Estimates of the line input impedance, Zin at a frequency ƒ, and the line capacitance ? are made. An estimate is then made in dependence of ?, the frequency ƒ and a value ?, where ? satisfies the relationship ? coth (?)=Zin·j??, and ?=2?ƒ. Accuracy may be improved by least squares fitting a curve to a set of intermediate values and then generating an estimate from the coefficients of the curve.

Abstract: While determining a leak resistance of a subscriber connection line provided, for example, with two wires in a communication network, a capacitor connected between two said wires is discharged prior to measuring leakage currents. For this purpose, prior to be connected to a high resistance of the other wire, the measurable wire and the other mentioned wire are supplied with a constantly falling and increasing voltage. For that, the final value of said tensions is determined in such a way that, when the connection to the high resistance of the other wire is produced, the voltage of said wire is equal to 0 volt. The leakage current is measured only when the discharge process is over, thereby making it possible to avoid an incorrect measurement caused by a current coming from the capacitor.

Abstract: A method and device for estimating one or more transmission properties of a telecommunication transmission line. At least one signal is sent on the line, the at least one signal including at least two frequencies for which the absolute value of the line propagation constant times the line length is less than ?, and a resulting signal is received. An estimate of at least one transmission line property is then determined by examining the relationship between the sent and resulting signal or signals. The process may be repeated, if necessary. The estimate determination may also be repeated one or more times, with each successive estimate preferably using for the determination only those frequencies for which, as previously estimated, the absolute value of the line propagation constant times the line length is less than ?.

Abstract: A method of testing a communication line includes measuring a first voltage/current couple on the communication line, measuring a second voltage/current couple different from the first couple on the communication line, and calculating a resistance based on the first couple and the second couple.

Abstract: A method and an apparatus for measuring electrical properties of communication lines is presented, wherein the communication line comprises a first line and a second line, wherein the first line is connected to a first line driver and the second line is connected to a second line driver. At least one measurement for determining said properties of said communication line is performed with the first line driver or the second line driver set to a high impedance state. With this method and apparatus, detailed line testing can be performed without the need for additional elements in a communication circuit.

Abstract: A power transformation device of a powered device in a power over Ethernet system includes a first transformer coupled between a first pin and a second pin of an Ethernet terminal, a second transformer coupled between a third pin and a sixth pin of the Ethernet terminal, and a bridge rectifier coupled between a center tap of the first transformer and a center tap of the second transformer, for rectifying power outputted from the center taps of the first transformer and the second transformer, so as to provide power for the powered device.

Abstract: A digital signal line echo reduction adaptor is configured to connect adjacent to a first end of a bridgetap line. The bridgetap line has a second end connected to a carrier communication line. The digital signal line echo reduction adaptor reduces an effect of echo from the bridgetap line on a rate of data transmission over the carrier communication line.

Abstract: A method and apparatus for mechanizing the currently manual ADSL loop testing process is disclosed. In one embodiment, an automated loop testing device is disclosed, where the loop testing device has a pair of terminals, e.g., RJ-11 jacks on both sides of the device. The jack on one side connects to inside wiring which, in turn, connects to an ADSL modem. The other jack connects to an outside line which, in turn, connects to a central office of a network provider. In operation, the present device detects a line voltage reversal and then disconnects the input line to the ADSL Modem. When the voltage returns to normal, then the device behaves normally by being closed, essentially acting as a pass through device and again connects the input lines to the output lines.

Abstract: Methods, systems, and articles of manufacture consistent with the present invention determine the type of damage to a wire, the amount of damage, and the location of the damage based on the wire's broadband impedance measured from a single measurement point. The type of damage is determined by comparing the wire's calculated dielectric function, resistance and inductance to known values that correspond to types of wire damage. The amount of damage is determined by comparing the wire's low-frequency impedance phase to known low-frequency impedance phase information that corresponds to a known amount of wire damage. The location of damage is determined by comparing the wire's high-frequency impedance phase to known high-frequency impedance phase information that corresponds to a known location of wire damage.

Abstract: Estimates of a communication system configuration, such as a DSL system, are based on operational data collected from a network element management system, protocol, users and/or the like. The operational data collected from the system can include performance-characterizing operational data that typically is available in an ADSL system via element-management-system protocols. Scanning, wherein a number of line profiles are used in connection with DSL loops having known configurations, can be used to generate a database or library of loop configuration information. One or more of the line profiles can be used with an unknown DSL loop to generate operational data from the unknown DSL loop that is compared to the loop configuration information in the database, allowing identification of loop configuration information pertaining to the unknown DSL loop.

Abstract: The present invention discloses circuits for isolating and attenuating signals generated by a telephone network. In disclosed embodiments, a metering pulse signal is isolated from the terminals of the connecting device, and then attenuated with an impedance that is synthesized with a programmable digital signal processor. Embodiments also utilize the digital signal processor to synthesize a termination impedance for the connecting device. The termination impedance matches closely the characteristic impedance of the network, so as to minimize wave reflections and the like.

Abstract: A method and apparatus for mechanizing the currently manual ADSL loop testing process is disclosed. In one embodiment, an automated loop testing device is disclosed, where the loop testing device has a pair of terminals, e.g., RJ-11 jacks on both sides of the device. The jack on one side connects to inside wiring which, in turn, connects to an ADSL modem. The other jack connects to an outside line which, in turn, connects to a central office of a network provider. In operation, the present device detects a line voltage reversal and then disconnects the input line to the ADSL Modem. When the voltage returns to normal, then the device behaves normally by being closed, essentially acting as a pass through device and again connects the input lines to the output lines.

Abstract: The present invention provides a method and apparatus for estimating the insertion loss of a telephone line. A complex waveform is applied to each wire of the telephone line being tested. Real and imaginary components of the resultant waveform are measured at a plurality of frequencies. Insertion loss of the line is estimated from a series of single-ended voltage measurements made at a plurality of frequencies. These measurements are captured and used to estimate the insertion loss of the telephone line.

Abstract: A system for qualifying subscriber lines in a telephony system for high speed data services. The system includes a measurement unit that makes one ended electrical measurements on the subscriber lines. Measurements on the subscriber lines are used to predict which of the lines can carry signals used in high speed data services. The predictions are used in marketing select data transmission services.

Abstract: Described is automatically testing the quality of an audio coupling between juxtaposed first and second digital telephones, e.g., VoIP telephones, such as to quantitatively determine the quality of audio echo cancellers in those digital telephones. An analyzer receives timestamps from a first telephone and second telephone during a calling session, including timestamps for when the second telephone initially provides audio (e.g., speech) to the first telephone, when the first telephone initially detects sound, when the first telephone initially provides audio to the second telephone, and when the second telephone initially detects sound. The analyzer uses the relative timing of the timestamps and the speech recognizer's outcome to determine whether the audio coupling is experiencing interference or echo. When the audio includes speech, a confidence level corresponding to accuracy of speech recognition also may establish the audio coupling's quality.

Abstract: A fault location system for a telecommunications network including a local exchange or switch, a node such as a primary connection point and a plurality of line terminations to the customer includes probability calculation to establish the location of a fault measuring from the exchange. Historical non-faulty reference values of capacitance are compiled for each line passing through the node providing a measure of the distance of each line. A lowest valid capacitance value provides an estimate of the reference capacitance between the exchange and the node. Using various parameters, probability tables are compiled of historic fault values and a new fault is compared against these tables to establish the probability of it being a fault at the node or elsewhere. As a result the reference capacitance can be obtained without the need for an engineer at the node, and the likely location of a fault can be pinpointed with greater accuracy.

Abstract: A method of testing a communication line includes applying a voltage as a function of time on the communication line and measuring at least a first current and a second current flowing via the communication line. The second current is measured at a different point in time than the first current. The method includes deciding whether a given terminal element is connected to the communication line based on the first current and the second current.

Abstract: The length and attenuation of a signal line between a transmitter and a customer premises equipment is to be estimated. A frequency dependent line input impedance (Zin(f)) as seen from the transmitter, is measured and an absolute impedance value (œ Zin(f) œ) is generated. The latter is shown as a curve (A1) in the diagram with the frequency (f) on the abscissa and the impedance (œ Zin(f) œ) on the ordinate. Extreme values (Max.1, Max2, Max3; Min1, Min2, Min3) arc denoted and a frequency distance (FD1-FD4) between two consecutive of the extreme values is generated. The line length (L) is generated as L=½·vop/FD1, in which vop is the velocity of propagation of a signal on the line. The attenuation is estimated by multiplying the line length with an average attenuation value for the actual line type. The advantages are that the line length can be estimated with good accuracy in a simple manner for short lines and that the line attenuation is estimated in a simple manner.

Abstract: The invention relates to a method for detection of impedances, in particular along inductances, in telephone lines of the type with two metal wires as signal conductors (twisted pair), having the following method steps: a test signal in the form of an AC voltage is fed into the telephone line, a measurement signal of the reflection signal of the test signal is measured, which can be tapped off the input impedance of the entire line at the start of the line, the first method steps are carried out at a number of different frequencies within a preselected frequency range of the AC voltage of the test signal, the profile of the measurement signals is analyzed as a function of the frequency, with the derivative of the profile of the measurement signals being formed based on the frequency, at which point the second derivative of the profile of the measurement signals is formed based on the frequency, the profile of the second derivative of the profile of the measurement signals based on the frequency is investigat

Abstract: A digital kick meter measures capacitive kick between two conductors and ground of a cable. The digital kick meter includes a resistance measuring circuit connectable to two of the conductors to provide a signal indicative of a capacitance between the two conductors. A filter is coupled to the resistance measuring circuit to filter a signal provided by the resistance measuring circuit, thereby producing a kick signal. Processing circuitry is coupled to the filter, and a graphical user interface (GUI) is coupled to the processing circuitry to display data related to the kick signal. The GUI may include an active bar graph dynamically displaying the kick signal on a graduated scale and retaining a peak value of the kick signal on the graduated scale.

Abstract: A method characterizes a customer line for data transmission. The method includes measuring electrical properties of the customer line from a central location, identifying a line model from the measurements, and identifying a modem model for a modem selected for use with the customer line. The modem model gives performance data for the selected modem. The method also predicts performance data for the customer line when operated with the selected modem by combining the line and modem models.

Abstract: The system and method of determining insertion loss of a telephone line under test (LUT) determines a first insertion loss as a function of plurality of different equivalent circuit values of the LUT determined at a plurality of different frequencies of a first set of discrete frequencies. A running standard deviation (rSTD) of a predicted length d of the LUT at each frequency of a second set of discrete frequencies is determined from the predicted lengths d of the LUT at and below said frequency. A second insertion loss is determined based on the pair of adjacent discrete frequencies of the second set of discrete frequencies that have the largest difference between their rSTDs. Based on a comparison of the first and second insertion losses to an expected insertion loss, one of these insertion losses is deemed to be the actual insertion loss of the LUT.

Abstract: A multi-unit test system performs automated and dynamically alterable, double-ended testing of telephone lines, whose service is provided on copper cable pairs. A prescribed set of (e.g., twelve) individual tests are executed either from a hand-held measurement unit, or by a central office-resident direct access test unit, or by a collaboration of the two. The hand-held measurement unit and the direct access test unit exchange FSK-based test control messages with one another that are effective to cause a selected electrical condition to be applied to a first portion of the wireline and to cause a prescribed electrical measurement to be made at a second portion of the wireline.

Abstract: A jack for a communications line can include first and second input terminals configured to receive respective first and second conductors of a communications line, and first and second output terminals electrically coupled to the respective first and second input terminals. The first and second output terminals can be configured to provide electrical coupling with respective first and second conductors of a communications device. A test switch can electrically couple the first and second input terminals responsive to activation thereof, and an indicator circuit can provide indication of a completed electrical circuit through the test switch.

Abstract: Systems and methods are disclosed for improving DSL performance, including ADSL and VDSL performance, over a local loop between a telephone company central office and a customer premises. In particular, a DSL repeater is coupled to the local loop and amplifies downstream and upstream DSL signals to at least partially compensate for DSL signal attenuation that occurs as DSL signals pass over the local loop. Pursuant to one embodiment, the DSL repeater includes a POTS load coil to improve the POTS, or voice band, transmission over the local loop. According to this embodiment, the DSL repeater provides both improved POTS band signal transmission and DSL service. One embodiment of the load coil includes a coupled inductor having compensating capacitors coupled thereto for counter-balancing the inter-winding capacitance of the coupled inductor. In another embodiment, the load coil includes a high intra-winding capacitance for counter-balancing the inter-winding capacitance of a coupled inductor.

Abstract: An optical submarine communication system has a land cable connected to a terminal apparatus which is installed on land near the seashore for transmitting an optical signal and electric power. The land cable is connected to an optical submarine cable through a beach manhole, and a repeater is connected to the optical submarine cable. The optical submarine communication system has a surge suppressor provided on the land cable, whereby a surge generated from the terminal apparatus side because of a lightning stroke or an insulation failure is suppressed and prevented from reaching and damaging the repeater.

Abstract: In the course of a reflectometry-based qualification procedure of a local loop, which connects customer premises to a central office of a telecommunication network, and in the event of being unable to identify the loop termination associated with the customer premises, a second reflectometry measurement of the local loop is carried out with a different impedance load at the customer premises. Next, the two reflectograms are compared with each other in the time domain in order to delineate among all the reflections those at the customer premises and to determine therefrom the position of the customer premises in the local loop.

Abstract: The method assesses the suitability of customer telephone lines (12, 13, 14) for data transmission. The method includes selecting a telephone line having tip and ring wires by means of a computer (30) and switch (15), and electrically connecting the tip and ring wires together at a test access (29) adjacent one end of the selected line to produce a common mode configuration. Single-ended electrical measurements are performed on the wires in the common mode configuration by a measurement unit (27) connected to the test access (29) to determine an electrical property of the wires from the measurements.

Abstract: To locate an open fault along a telecommunication wireline pair, a prescribed frequency tone is coupled to the wireline pair by way of a center tap of the transformer through which a line card is coupled to a subscriber loop. The line card's analog front end conducts capacitance to ground measurements on the tip and ring segments of the wireline pair. From these measurements, sum and difference distance values of respective tip and ring conductor lengths are derived. The sum and difference distance values are then processed to calculate the distance to the fault.

Abstract: An electronic driver circuit for a directly modulated semiconductor laser has a first circuit for generating a constant current and second circuit for modulating the constant current in dependence on a digital data signal. The modulated current forms a laser current that drives the semiconductor laser. An optimal signal shape of the modulated current is guaranteed to the greatest possible extent, even in the case of high modulation frequencies above one Gbit/s, by way of a third circuit that is connected in parallel with the semiconductor laser. The third circuit acts as an ohmic resistance with a high impedance for direct current and with a low-impedance for alternating current with the modulation frequency.

Abstract: SELP techniques that provide an accurate estimate of the length of a transmission medium (e.g., subscriber loop in a DSL system) are disclosed. A probe signal is transmitted over the transmission medium at one or more frequencies. A reflected version of the probe signal is then received. Transmission medium impedance is determined based on the ratio of the reflected version of the probe signal and the transmitted probe signal. An estimate of transmission medium length is determined by comparing its impedance to a plurality of predetermined impedances, each of which is associated with a transmission medium having known length. Thus, the length of the systems transmission medium is identified. The transmission medium impedance can also be used to identify the presence of load coils and short circuits in the transmission medium.

Abstract: A characteristic of a local loop is used to estimate the loop's data carrying capacity. The characteristic is measured and applied to a table previously stored in memory which contains values relating the characteristic to downstream data rates. Using interpolation when required, an estimate of the data carrying capacity of the local loop is estimated based on the measured characteristic. The measured characteristic may be, for example, the input impedance or the DC resistance of the local loop.

Abstract: A computer-executable method for diagnosing trouble causes in telephone cable segments when trouble data are available only for entire cables is presented. This method diagnoses problems in the components of processes when the component location of process problems is not known. It gives a statistical relationship between component attributes and process problem rates, to facilitate assessment and improvement of policies about the process. This method may be used for diagnosing systematic problems in segments of telephone cable connections of given central offices.

Abstract: The present invention synthesizes a prescribed impedance. The impedance is synthesized by generating a current having a value substantially equal to a voltage divided by a prescribed impedance. Sensing the line voltage and converting that sensed line voltage to its digital equivalent accomplish this first step. The digital line voltage is processed by a factor related to the prescribed impedance to produce an output voltage that has a value substantially equal to the sensed voltage divided by the prescribed impedance. The output voltage controls a voltage to current converter that generates the appropriate current across the points or terminals where the line voltage was measured. Thus, the prescribed impedance is generated across these points or terminals because the line voltage divided by the generated current is substantially equal to the prescribed impedance.

Abstract: A communications device can include first and second input terminals configured to provide coupling with respective first and second conductors of a communications line, and first and second signal conductors respectively coupled with the first and second input terminals. A communications circuit can be coupled to the first and second signal conductors wherein the communications circuit provides a communications interface. A test switch can be configured to electrically couple the first and second signal conductors responsive to activation thereof, and an indicator circuit can be configured to provide indication of a completed electrical circuit through the test switch. Related circuits and methods are also discussed.

Abstract: A method and system are provided for automating the dispatching of maintenance services from a telephone cable air pressure monitoring system. If air pressure maintained in a telephone cable conduit drops below a required level, an alarm may be generated at an air pressure alarm and report system (APARS). If the APARS determines that an unacceptable air pressure exists, data associated with the cable conduit is sent to a proactive maintenance application (PMA). The PMA checks other data associated with the conduit in question to determine if an acceptable condition exists that is responsible for the drop in air pressure or air flow. If the PMA does not determine that the change in air pressure or air flow is acceptable, the PMA generates a work order or work ticket for ordering a repair of the conduit. The work order is transmitted to a dispatch system. At the dispatch system, an operator verifies the status of the conduit in question.

Abstract: A ‘lifeline’ POTS back-up mechanism is operative to provide emergency plain old telephone service connectivity over a span-powered two-wire metallic digital subscriber loop pair, in response to a customer's phone going off-hook, during a lack of normal operating condition of the digital circuit path. A ground fault interruption signal is generated in a remote terminal and used to activate respective POTS by-pass paths in the remote terminal and a central office terminal.

Abstract: Line states are detected accurately to efficiently test subscriber lines, thereby improving the reliability and quality of maintenance and operation. Line monitoring means monitors line states based on at least one of loop information of lines and status information of bearer channels. Subscriber line testing means conducts subscriber line testing in accordance with the line states.

Abstract: The invention relates to a device for assisting in the measurement of the earth resistance comprising a ground rod with a wire coiled up on a reel or the like, and electrical connecting means for connecting the wire to the ground rod. To provide such a device which is practical to handle, simple, small, and capable of being produced at low costs, it is provided for the reel or the like to be rotatably mounted on the ground rod. A further improvement results in that the ground rod comprises an offset portion in whose region the reel or the like is rotatably mounted. Preferably, the electrical connecting means between ground rod and wire comprise sliding rings on the rotation axis, the reel or the like. For an rapid exchangeability of the reel, the latter may be mounted on the ground rod by a snap connection.

Abstract: The invention presented herein is directed to a battery injection and loop supervision (BILS) system and method that can be used in the DSL environment. The BILS of the present invention provides battery injection, loop supervision, and butt set operation mode detection in the DSL environment. A voltage source, detector and comparator in the BILS unit can be used to supervise the copper loop status from the central office. In addition, using the present invention, a field technician using a conventional butt set can detect battery voltage and receive an audible tone from the cooper loops in the DSL environment. Furthermore, the BILS can be implemented in accordance with two preferred embodiments, voltage sensing and current sensing. The BILS includes circuitry, working in conjunction with a shared common resource card and a conventional butt set, for testing, maintaining, and installing copper loops in the DSL environment.

Abstract: An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz due to the customer's terminal equipment from an ADSL network unit and/or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points.

Abstract: An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz due to the customer's terminal equipment from an ADSL network unit and/or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points.

Abstract: An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz a desired frequency range due to the customer's terminal equipment from an ADSL a DSL network unit and/or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points.