Abstract: A communication line diagnostic unit (10, 10') that allows telephone central office equipment to perform a test of a communication line and determine the ability of the line as a communication medium is shown. The device is completely passive and transparent during normal operation and responds only to a unique trigger signal generated from the central office verification controller (VC). The unit is powered from a capacitor storage element (C1) charged by the communication line through an AC coupling network (pins 11, 12 and 8) as well as through a DC network comprising voltage regulator device (Q2; Q23; Q24, Q25) when the unit is awakened. Upon receipt of the trigger signal the device responds as by disconnecting the subscriber apparatus and then providing certain electrical terminations through a single solid state switch (Q10) to allow for identification, loop resistance, noise and frequency response measurements.

Abstract: A telephone wire pair is qualified for digital signal transmission by central office testing. The tip-to-ring capacitance of the wire pair is measured while applying to the wire pair an AC test signal at 600 Hz. The test signal at this frequency minimizes errors due to line inductance and/or a ringing device connected to the wire pair. Reliable measurement of the length of the wire pair is achieved. Flaws in cable sheathing can also be detected based on measurement of tip-to-ground capacitance and/or ring-to-ground capacitance.

Abstract: A measurement method and measuring circuit are described for high-speed measurement of subscriber line impedance without the influence of counter electromotive force of the bell circuit or hum noise. A measurement current is supplied from a controlled-current source to each of a pair of subscriber lines by way of switches, and subscriber line voltage and current values are measured during the transient state. A measurement time interval is divided into a first-half and a second-half interval, the average values of the voltage and current are detected for each time interval, and moreover, the difference between voltages at the beginning and end of each time interval is detected. In this case, the controlled-current source is controlled by a control means such that the rate of change of the current value over time remains at or below a fixed value.

Abstract: A switching device for a telecommunications channel. The device comprises a voltage detector, a switch, and a storage device. The voltage detector produces an output voltage if the voltage between the lines of the channel exceeds a predetermined level, for example 110 volts. The switch can increase an impedance in one of the lines (preferably causing open circuit) in response to an input voltage. The first storage device, for example a capacitor, produces the input voltage when it reaches a charge V.sub.2 ; is initially at a voltage V.sub.1, for example zero, that is less than V.sub.2 ; after charging by the output voltage from the voltage detector, is at a voltage V.sub.3 greater than V.sub.2 ; and discharges from V.sub.3 to V.sub.1 in the absence of the output voltage. The voltage detector comprising a low-pass filter such that an AC signal on the channel produces an output voltage that charges the first storage device to a charge below V.sub.2.

Abstract: A circuit and method for maintaining switch-hook detection (SHD) in the presence of a fault in a telephone system may include a comparison of one of a tip current and a ring current to a reference current. A switch-hook detection indicates that a request for service has been made. The reference current may be a conventional switch-hook detection threshold current, I.sub.SHD, times a factor (G.sub.0 +1).sup.-1, where G.sub.0 is the predetermined operating gain of the amplifier in the telephone subscriber line interface circuit. The line current may be reduced in response to detection of a fault in the telephone system without affecting the determination whether a request for service has being made.

Abstract: An improved system for minimizing toll charges is disclosed wherein line quality is measured and a call is terminated if the line quality is not at an acceptable level to allow for the highest possible bit rates during data transfer or to guarantee a certain minimum degree of quality.

Abstract: The portable line test telephone of the present invention consists of the switching means to operate different kinds of tests, the high voltage generating means to measure telephone capacity and insulation resistance, the dialing means to call and the call circuit means to talk with a subscriber or the called. Accordingly, line operator can make direct tests and examine telephone capacity, earth, line disconnection, line cross, insulation resistance with calling and talking with a subscriber.

Abstract: A current detector for connection in series with a lead carrying current to be detected, has a first branch with a plurality of series connected diodes having an anode end and a cathode end for connection to the lead, a first optocoupler light emitting diode connected in series with a resistor, connected in parallel with the first branch, the optocoupler diode being connected in the same polarity direction as the diodes in the first branch, and a first further diode connected in parallel with the first branch, in opposite polarity direction as the diodes in the first branch.

Abstract: A circuit for sensing telephone line conditions, comprising: high impedance termination means across the telephone line; means for accumulating charge through the high impedance termination means; and electrical isolator means intermediate the means for accumulating charge and voltage detecting means.

Abstract: An apparatus for testing the racks and installation wiring of telephone switch equipment takes the form of a module capable of insertion into the various slots of a particular rack configuration. The module includes a circuit board which terminates in a connector suitable for interconnection with a particular telephone switch system, and which receives a continuity testing subassembly useful in performing the desired testing. To this end, selected contacts (or pins) of the connector are coupled with a light emitting diode (LED) and a biasing circuit for operating the LED responsive to connection of the biasing circuit to ground. Each LED, and the biasing circuit, is provided with a suitable operating voltage which can either be derived from the rack which is being tested or a battery which is resident in the test apparatus.

Abstract: An electrical test kit for testing a telephone line from the terminals at the customer's end of the line includes a circuit for testing line continuity without falsely indicating to the voltage source that a telephone call has been answered, a push-button selection switch and a parallel pair of light-emitting diodes connected in reverse polarity relative to each other for determining polarity of the telephone line, and test pads in parallel with the continuity test circuit for permitting the attachment of a voltmeter so as to determine the magnitude of the internal resistance of the telephone line.

Abstract: A network termination unit for connection to a telephone line at a predetermined demarcation point for sequentially simulating a plurality of fault conditions to allow a diagnostic routine to be performed on the telephone line at a remote location from the demarcation point. The network termination unit comprises a plurality of semi-conductor switches electrically connected to conductors of the telephone line to establish a network of electrical paths capable of altering the electrical condition of the telephone line when caused to assume a state of conduction. A logic module causes the switches to assume either a closed or an opened condition in accordance with a predetermined sequence established by a hard-wired program.

Abstract: A maintenance termination unit (MTU) for use in telephone circuits. The MTU comprises a switching arrangement which can be connected in a communications channel, the communications channel comprising a pair of lines. The switching arrangement is connected between a set of exchange-side terminal equipment and a set of subscriber-side terminal equipment. The arrangement comprises first and second line switches, each of which is series connected in one of the lines. Each line switch comprises a control terminal, and has a closed state in which it will pass normal line current, and an open state in which it will pass at most a reduced line current. The arrangement also comprises a control circuit which is connected to the channel between the line switches and the subscriber-side terminal equipment.

Abstract: A power-cross detection circuit includes a zero crossing detection circuit for detecting a first zero crossing of the current from a first positive half-cycle to a first negative half-cycle, a second zero crossing of the current from a second positive half-cycle to a second negative half-cycle, and a third zero crossing of the current from a third positive half-cycle to a third negative half-cycle and a circuit for detecting a voltage level and outputting a first signal when the voltage level exceeds a predetermined voltage level, between the first zero crossing and the second zero crossing and between the second zero crossing and the third zero crossing. The zero crossing detection circuit outputs a second signal based on the first, second and third zero crossings.

Abstract: For measuring characteristics (resistance, capacitance, and foreign voltage) on a telephone line, source voltages are coupled via source resistances to the line in three test conditions and the parameters are calculated from steady state voltages at the terminals of the line. Each steady state voltage is predictively calculated from nine samples of the voltage at the terminal using a closed form second order solution of a circuit model of the telephone line derived from a transformation of the circuit model into the Z domain and using the matched pole-zero technique. The steady state voltages can thus be determined without waiting for transients, due to the time constants of the telephone line, to die out, resulting in much faster measurements for telephone lines with large time constants.

Abstract: Resistive faults are analyzed on a conductor in a telephone line by first charging the conductor to an initial voltage. The conductor is allowed to float for a finite amount of time, allowing some of the charge on the conductor to leak through any resistive fault. Then, the voltage of the conductor is measured and compared to the initial voltage. Loss of voltage indicates a resistive fault. This information can be used to provide an indication of the accuracy of a capacitance measurement and can be used to correct the capacitance measurement to account for the error due to the resistive fault.

Abstract: A device, for digitally measuring in real-time analog telephony signals appearing on a subscriber line during a telephone call thereover, having a converter for converting analog subscriber line voltages into corresponding digital samples, a memory for storing a number of these samples and a processor which resides in any one of various states. For each such state, the processor generates at least one different mask condition, the condition being a limit value of a pre-defined characteristic of at least a particular one of the stored digital samples relative to other such samples. The processor occupies various states with the selection of any one of these states depending upon a particular previous and/or subsequent history of the line voltages with respect to that call, i.e. the state of the call. The processor checks whether some of the stored digital samples satisfies the mask condition.

Abstract: A network termination unit for connection to a telephone line at a predetermined demarcation point thereof for sequentially simulating a plurality of fault conditions to allow a diagnostic routine to be performed on the telephone line at a remote location from the demarcation point. The network termination unit includes a plurality of semi-conductor switches electrically connected to conductors of the telephone line to establish a network of electrical paths capable of altering the electrical condition of the telephone line when caused to assume a state of conduction. A logic module causes the switches to assume either a closed or an opened condition in accordance with a predetermined sequence established by a hard-wired program.

Abstract: A microprocessor-controlled voltage source selectively provides to a telephone line either a DC or an AC voltage, prescribed characteristics of which are programmably adjustable, enabling test equipment to controllably condition and test the line with essentially any desired line conditioning voltage or signal waveform. A digital-to-analog converter (DAC) provides an output voltage having an amplitude that is digitally programmable. This output voltage is available to be applied either directly or through controlled amplifier circuitry to the line. In order to generate an AC signal having both an adjustable amplitude and waveform characteristic, the output of the DAC sets the amplitude for a combination of signals from a plurality of squarewave generators having programmable frequency characteristics. The output of the combining unit is coupled to a switched capacitor filter which filters the controllably-interrupted, digitally-controllable output voltage, (e.g.

Abstract: A connector unit (21) for automatically terminating a digital data services (DDS) line whenever a mating modular plug (30) is not inserted into the connector. The connector utilizes a switchable DDS jack (25) that mates with the modular plug (30) for connecting a data-transmit line and a data-receive line of a DDS network (41) to a customer's equipment (45). The connector unit has a maintenance termination circuit (40) with terminating impedances (r, r1, C and C1) and diodes (D and D1). When the plug and jack are not engaged, the maintenance termination circuit is connected to the data-transmit and data-receive lines via the normally closed jack contacts (33 and 34). As the plug and jack are engaged, the plug abuts against and, as movement continues, increasingly opens the jack contacts, causing the maintenance termination circuit to be disconnected from the customer's equipment and to be connected to the DDS network.

Abstract: A device and method for line impedance measurement using a multi-frequency test signal waveform in a signal injection technique featuring analysis of acquired line test response data. A multi-frequency test signal waveform is injected into the susbscriber line, to obtain by data acquisition the line response in terms of voltage measurements, which are processed via a digital filter to analyze a specific sine wave frequency. For example, if a multi-level rectangular wave signal is used as the test signal, it does not necessarily have a symmetrical waveform, and the analysis may be made at the dominant frequency derived from the rectangular wave, or other harmonics. For the frequency chosen for the analysis, it is possible to derive the line characteristics, including amplitude attenuation and phase shift, which constitute the line impedance.

Abstract: A device for testing line connections at a telephone exchange includes a combined generator and comparator for generating a bit sequence of pseudo-random type and for comparing a received bit sequence to a generated bit sequence. A generated bit sequence is through a line connection forwarded to a telephone set and back again to the generator and comparator, where the received sequence is compared to the forwarded one. The number of bit errors occurring in the transmission is a measure of the transmission quality of the connection. A selector device selects one of several line connections which is to be tested. Only one testing device is required for testing a number of line connections which through the same pair of one serial output line and one serial input line are connected to a telephone exchange.

Abstract: A fault locating method and submarine equipment for detecting the location of a fault developed in a communication system including an optical submarine cable and submarine equipment such as repeaters and branching units inserted in the cable, which is supplied with operating current via a feed line of the cable. The submarine equipment has a main processing circuit for transmitting signals via the submarine cable; an power unit inserted in the feed line so as to supply operating power for the main processing circuit by receiving the operating current from the feed line; a nonlinear resistance device which is connected to the feed line and the resistance value of which increases as a current flowing through it decreases, and a charging/discharging resistor disposed in parallel to the nonlinear resistance device. The fault locating method detects the location of an open-circuit fault occurring in the cable by measuring the capacitance of the open-circuit cable.

Abstract: For measuring characteristics (resistance, capacitance, and foreign voltage) on a telephone line, source voltages are coupled via source resistances to the line in three test conditions and the parameters are calculated from steady state voltages at the terminals of the line. Each steady state voltage is predictively calculated from nine samples of the voltage at the terminal using a closed form second order solution of a circuit model of the telephone line derived from a transformation of the circuit model into the Z domain and using the matched pole-zero technique. The steady state voltages can thus be determined without waiting for transients, due to the time constants of the telephone line, to die out, resulting in much faster measurements for telephone lines with large time constants.

Abstract: A junction box for coupling alligator test clips to a modular telephone line. The device includes a housing having a plurality of contacts to which each alligator clip of a telephone testing apparatus may be connected. A female modular telephone receptacle is provided having a plurality of color-coded wires electrically coupled to the respective contacts. The contacts are each labeled in accordance with conventional telephone wire colors. The telephone testing apparatus may be easily coupled to a male modular telephone connector of the telephone line to be tested. The device eliminates the conventional practices of moving furniture to access telephone outlets, and disassembling telephones for access to internal contacts.

Abstract: A method of measuring under running conditions operation parameters of an interface circuit and a telephone subscriber line connected to it, said interface circuit comprising a first integrated circuit operating on a high voltage with outputs connected to the line and second outputs on which transverse and longitudinal current values of the line are respectively present in normal operation, and a second integrated circuit operating on a low voltage between the first circuit and a telephone exchange, comprises the steps of: switching the outputs across an impedance of a predetermined value, and measuring through the first circuit the values of the currents present on the second outputs; switching said outputs back to across the line leads, and measuring through the first circuit the values of the transverse and longitudinal line current values; performing, for each measurement through the second circuit, a digital encoding of the measured values and transmitting such encoded values to the telephone exchange.

Abstract: An open power loop detector for digital transmission line elements using a pulsed, direct current test. The element detects when a fault in transmission lines has been corrected and the element should move from a loop powered mode back to a normal through powered mode. The detector includes a voltage regulator, voltage booster, current detector, and controller. The controller periodically activates the voltage booster to increase the direct current load between the transmit and receive cable pairs of the transmission lines. The current detector then senses whether a current is flowing between the center tap leads of the transmit cable pair. If no current is detected, indicating that the downstream transmission line still has a discontinuity, the controller waits a predetermined period of time before again activating the voltage booster and performing another test.

Abstract: The potential impedance mismatch of digital terminal equipment and a line test unit that has been equipped to conform with the Bellcore standard of terminating the line with a 600-900 ohm impedance during data reception is addressed by modifying the craftsman's test unit to include a controllably disabled AC impedance, which is operative to normally bridge the tip and ring leads of the telephone circuit under test with the required (600-900 ohm) impedance during data reception and, under direct control by the craftsman's keypad or software control resident in the test set's microcontroller, to selectively remove the AC matching impedance that would otherwise bridge the line. The AC impedance is comprised of a D.C. blocking capacitor and a resistor coupled in series with a controllable solid state relay which is normally rendered conductive during data reception to bridge the tip and ring leads.

Abstract: For obtaining a longitudinal balance of a pair of relatively long wires, a sinusoidal stimulus signal is generated by processing digital reference signals and is applied to the pair in at least two different connection profiles. Voltages at each wire are measured in each connection profile and are combined with the digital reference signals to derive drive representative values and metallic representative values of the pair of the long wire. The longitudinal balance is calculated from these representative values. The invention requires no highly balanced circuit to provide highly accurate measurements. The measurement inaccuracies and inherent unbalance of the measuring circuitry are eliminated by the use of at least two connection profiles and signal processing.

Abstract: In digital measurement of the amplitude and phase of a sinusoidal signal of known frequency by the least square error method, the sampling frequency and sample size are carefully selected to satisfy a certain relationship. Under these conditions, the measurements are simplified and accuracy improved. This technique of measuring a sinusoidal signal is applied to the detection of a load coil in a telephone subscriber's loop circuit. The magnitude and phase of the driving point impedance of the loop are measured through the use of a series of discrete sinusoidal stimulus signals of predetermined frequencies and a digital signal processing technique.

Abstract: There is a demand for user access to ISDN services at the two-wire interface point. The frequently raised objection to such access is the problem of determining the location of a fault and hence the responsibility for the fault. This is solved by the use of a voltage sensor responsive to a DC voltage less than a normal line feed voltage within a voltage range not used in normal operation to control a switch operative to disconnect a subscriber termination unit from the line, and to provide a known linear terminating impedance for the line for the duration of the application of the DC voltage.

Abstract: A subscriber equipment (210) is isolated (238, 234) at a line card (208) in a line shelf (200) and drop testing is conducted over a test-out bus (240) by a test unit (220) connected (236) to the subscriber equipment (210); the test unit (220) may be plugged into any line card slot in any of a plurality of line shelves (200, . . .

Abstract: A system and method for testing equipment in a telephone network is disclosed for remote maintenance and verification of subscriber loops. The system and method accommodates known AC and DC fault testing techniques while improving reliability by providing duplex verification of the subscriber loop identification.

Abstract: An apparatus for monitoring and testing a twisted pair, particularly useful for an Ethernet network. First and second DC currents alternated with one another are applied to both ends of the line, asynchronously. By monitoring the potential on the line, a determination is made as to the condition of the line. For example, shorted, crossed, improperly terminated or open conditions can be detected. A visual indication of the condition of the line is provided and additionally, the visual indication provides an indication of the traffic level in the network.

Abstract: Circuitry is provided for testing telephone lines, the circuitry comprising a loop current ring trip detector and a relay which in operation is used to break normal current to provide an end of call indication, and wherein said relay is also operative in one test mode to switch from said loop current ring detector to a comparator which functions as a test mode detector. The means may also include a second relay which when the circuit is in a second test mode is operated simultaneously with the first relay, the second relay being connected to a bell capacitor the discharge rate of which can be measured by said capacitor, and the comparator output is sequentially monitored to provide information as to the condition of the insulation and regarding bell capacitor and terminal connection.

Abstract: In a bidirectional communication channel, the method and apparatus for determining directionality of communication signals using digital techniques. A plurality of independent signals are derived from the communication channel, which signals are analyzed to determine their relative phase(s). The relative phase(s) are then compared with a table of relative phases indicating the directionality of the original signals.

Abstract: An apparatus for monitoring and testing a twisted pair, particularly useful for an Ethernet network. First and second DC currents alternated with one another are applied to both ends of the line, asynchronously. By monitoring the potential on the line, a determination is made as to the condition of the line. For example, shorted, crossed, improperly terminated or open conditions can be detected. A visual indication of the condition of the line is provided and additionally, the visual indication provides an indication of the traffic level in the network.

Abstract: The equipment includes a front panel with LED indicators, key pad and a number of special function keys as well as an LCD message printout and volt/ohm meter. A hand set is readily available at the front panel as the line check unit functions with a commercially available craft terminal, a CMC Type 7910D terminal known as DATASTAR.TM., which includes the master central processing unit and random access memory for interactive function with the line check system. The DATASTAR.TM. unit communicates directly with a controller section that includes speaker power amp, LCD circuitry and 128K random access memory as well as a digital bus interface. The controller board is then connected through both a digital bus and an analog signal bus to an analog circuitry that includes relay control and various signal routing and test signal functions. The analog circuitry is then in communication with the volt/ohm meter and analyzer circuitry.

Abstract: A novel method and improved system for the continuous detection monitoring of authorized/unauthorized connections/disconnections including loop bridging wiretapping equipment capable of monitoring recording voice and/or data communications on the subscriber's local telephone loop.In operation the detector monitor displays electrical changes in impedance condition and characteristics on the subscriber's local telephone loop to detect and monitor signaling, switching equipment and telephone lines connecting/disconnecting anywhere on the loop including the central exchange before, during and after the completion of a telephone call continuously.

Abstract: A method of testing a telephone line including installing a test call unit at an end of the telephone line at which a customer's equipment is connected, automatically initiating a telephone line test at the module, performing the telephone line test, and transmitting the results of the line test over the telephone line.

Abstract: A subscriber line measuring method and apparatus can charge a line capacitance of a telephone subscriber line in a very short time as compared with a prior art by charging the line capacitance by a predetermined current without use of a high resistor (100 k.OMEGA.) in a conventional measuring apparatus, and thereby can measure an impedance of the telephone subscriber line in a very short time with high accuracy.

Abstract: The present invention relates to a method for distinguishing between an open conductor and a proper termination of a telephone subscriber loop which is terminated with a telephone which does not conform to the ringer-equivalence standard of the FCC Rules. In this invention a telephone subscriber loop can be tested for an open or for a termination by a customer provided equipment telephone by obtaining a first ratio of the tip-to-ground impedance relative to the tip-to-ring impedance; and a second ratio of the ring-to-ground impedance relative to the tip-to-ring impedance, and comparing each of these ratios relative to a fixed ratio value. If the measured ratios are substantially equal to or greater than the fixed ratio value, the subscriber loop is terminated with a customer provided equipment telephone. The fixed value may be dependent upon the length of the loop and whether or not a maintenance termination unit is present in the loop.

Abstract: The present invention interrupts the service after the entire preparation process, and executes testing process after interconnecting the line to the test equipment, and recovers the line as service possible as soon as the test is ended. As a result, the minimum amount of service time is killed by the test. On the test by line maintenance personnel, the present invention reports the personnel about the status of the line by an instant test just after doing hook-on following the ring sent from the exchanger in a specified time. So, the line maintenance personnel can verify the status of the line at instantaneously.

Abstract: Test apparatus for signalling systems having plural terminal units (26X) and line-pair connections (24X) therefor, comprises off-line test equipment (10) for parameters or conditions of said connections (24X), and connection means (30) of or for the test equipment (10) relative to said system. The connection means (30) comprising plural connectors (32X, 34X) as inputs for a number of said connections (24X) to said terminal units and multi-way switch means (40X) affording selection of said inputs (32X) one at a time for communication with other facilities of said off-line test equipment (10).

Abstract: Before each actual resistance measurement, a first preliminary measurement with short-circuited measuring circuit and a second preliminary measurement with the measuring circuit operating at no-load are carried out. From the measured values of the preliminary measurement steps, a weighting factor is calculated, by which, subsequently, the difference between the actual measured value and the short-circuit value is multiplied to form the actual measurement results.

Abstract: A simple impedance measuring tool is provided for performing an accurate but inexpensive determination of impedance and assurance of an impedance match in an installation environment. The apparatus operates according to a method wherein the average instantaneous voltage on a transmission line is sensed based on the integration of a series of reflections stimulated by a pulse generator. The apparatus comprises a fast repetitive pulse generator, a fast comparator, a flip-flop and a means for integrating the output of the flip-flop to produce an output voltage which can be read by a simple low-cost meter such as a d.c. voltmeter. The output of the comparator is coupled to the data input of the flip-flop, which is driven at its clock input by a variable phase clock output of the pulse generator. The absolute time delay or phase determines the distance at which the measurement is to be taken.

Abstract: A method of locating faults in a telephone system including the steps of connecting antiparallel rectifying switches (ARS's ) that inhibit alternating current (A.C.) flow in one direction but not the other between subscriber equipment and respective telephone company lines, applying an A.C. test signal to a telephone company line and measuring a resulting signal, and determining whether a fault is on the telephone company line or customer equipment based upon the resulting signal. Also disclosed is an ARS that includes a first input and output, a second input and output, and paths between respective inputs and outputs providing low turn-on thresholds in one direction between respective inputs and outputs and high turn-on thresholds in the other direction, the directions of low and high being the same for both sets of inputs and outputs.

Abstract: A method for measuring line parameters of subscriber lines of a telecommunication system in which end devices, exhibiting a capacitance, are connected to two wires of the subscriber lines is disclosed. The line parameters measured include the capacitances between each of the line wires and ground, the capacitance between the line wires, the leakage resistances between each of the line wires and ground, and the insulating resistance between the line wires. This task is accomplished by performing the following steps while the end device is connected to the subscriber lines. These steps are performed in three measuring configurations sequentially: first one of the two wires of the subscriber line is grounded and the measurement is performed in connection with the other, then the other one of the two wires is grounded and the measurement is performed in connection with the first, and then both wires of the subscriber line are connected together and the measurement is performed on the pair.

Abstract: There is disclosed a circuit for monitoring a capacity of a subscriber line to which a capacitor equivalently representative of a telephone set is connected. This monitoring circuit has a test sequence for the subscriber line capacity. The test sequence comprises a first step to connect the subscriber line to a test circuit, and second step to apply a backward voltage to the subscriber line, thereby to discharge an electric charge stored in the equivalent capacitor. The test sequence further comprises a third step to apply a forward voltage to the subscriber line through a reference capacitor, thereby to charge the equivalent capacitor to evaluate the capacity value of the equivalent capacitor on the basis of a voltage appearing across the equivalent capacitor, thus to effect a capacitive test of the subscriber line.

Abstract: A cable analyzer is capable of having a group of 25 pairs of wire from a telephone cable connected by a module to the analyzer. By a central processing unit or computer in the analyzer, a series of relays connect any one of the pair of wires to a routing board. At the routing board, a plurality of analog tests may be directed to be conducted upon the pair of wires and ground, or the wires may be routed within the analyzer for other purposes. The results of the analog tests are converted to binary digital format so that they may be analyzed by the central processing unit. The results are visually displayed or printed. The central processing unit has the capabilities, through different programs, to conduct a plurality of tests upon each pair, and upon the completion of the plurality of tests, proceed to a subsequent pair for a plurality of tests.