United States Patent
`
`[19]
`
`Williams
`
`llllllllllllllIllIllllIllllIlllllllllllllllllllllllllllllllllllllllllllllll
`U8005189663A
`
`[11] Patent Number:
`
`5,189,663
`
`:3
`
`[45] Date of Patent:
`
`Feb. 23, 1993
`
`[54] METHOD OF AND SYSTEM FOR REMOTE
`TESTING AND REPORTING OF ISDN LINE
`CONDITIONS
`
`4,922,482
`4,939,202
`4,998,240
`
`5/1990 Tanahashi et a1. .................... 370/13
`
`1/1991 Soto etal. ............. 370/13
`3/1991 Williams ........................... 370/1101
`
`[75]
`
`Inventor: Clifton B. Williams, Richmond, Va.
`
`[73] Assignee: C & P of Virginia, Richmond, Va.
`
`[ ‘ ] Notice:
`
`The portion of the term of this patent
`subsequent to Mar. 5, 2008 has been
`disclaimed.
`
`[21] Appl. No.: 515,007
`
`[22] Filed:
`
`Apr. 26, 1990
`
`Related US. Application Data
`
`[63]
`
`Continuation-impart of Ser. No. 394,090, Aug. 15,
`1989, Pat. No. 4,998,240.
`
`[51] , Int. Cl.5 ................................................ 1104.] 3/14
`[52] US. Cl. ........................................ 370/17; 370/13;
`371/201
`[58] Field of Search ........................ 370/13, 110.1, 17;
`371/201, 20.5, 8.1
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,611,320 9/1986 Southard ............................... 370/15
`
`4,663,754
`5/1987 Senoo ................
`370/13
`
`3/1988 Stephenson et al. ............... 370/94.1
`4,730,313
`
`Primary Examiner—Benedict V. Safourek
`Assistant Examiner—Min Jung
`Attorney, Agent, or Firm—Lowe, Price, LeBlanc &
`Becker
`
`[57]
`
`ABSTRACT
`
`In an integrated services digital network (ISDN), a
`selected customer ISDN line at a central office is tested
`by remote control from an ISDN testing facility so that
`it is unnecessary to dispatch service personnel to the
`office to carry out the test. At least D-channel data from
`the ISDN line to be tested is obtained from the standard
`
`U-interface bus, accessed at the central office using the
`line card sparing feature of a standard integrated ser-
`vices line unit (ISLU). The D-channel data is applied to
`a personal computer at the central office, programmed
`to carry out protocol analysis and to supply at least one
`of data indicative of the protocol analysis and raw data
`used to perform the protocol analysis to a report com—
`munication line. Another computer at the ISDN test
`facility controls the operation of the computer at the
`central office over a dedicated communication line.
`
`26 Claims, 5 Drawing Sheets
`
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`

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`US. Patent
`
`Feb. 23, 1993
`
`Sheet 1 of 5
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`5,189,663
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`US. Patent
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`Feb. 23, 1993
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`Sheet 2 of 5
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`5,189,663
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`US. Patent
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`Feb. 23, 1993
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`Sheet 4 of 5
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`US. Patent
`
`Feb. 23, 1993
`
`Sheet 5 of 5
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`5,189,663
`
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`ISDN
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`

`1
`
`5,189,663
`
`METHOD OF AND SYSTEM FOR REMOTE
`TESTING AND REPORTING OF ISDN LINE
`CONDITIONS
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application is a Continuation-In-Part application
`of, and claims priority from, US. patent application Ser.
`No. 07/394,090 entitled “Method of and System for
`Remote Testing of Integrated Service Digital Net-
`works” filed on Aug. 15, 1989, now US. Pat. No.
`4,998,240.
`
`TECHNICAL FIELD
`
`15
`
`The present invention relates generally to testing of
`integrated services digital networks (ISDN), and more
`particularly, to a method of and system for remote and
`unattended testing and reporting of the condition of 20
`customer ISDN lines at an unmanned central office.
`
`BACKGROUND ART
`
`2
`A number of communication channels are established
`between the central office and ISDN subscriber; the
`transmission structure consists of a pair of B-channels
`each carrying 64 kilobits per second of data and a D-
`channel that carries 16 kilobits per second of data. The
`B-channels in practice are used to carry digital data,
`pulse code modulated encoded digital voice or a mix-
`ture of lower rate traffic including, optionally, packet
`switched data. The D-channel carries common channel
`10 signalling information to control circuit switched calls
`on associated B-channels at the user interface, and may
`also carry packet switching or low-speed telemetry.
`Data on the D-channel provides information to the
`central office switch on status of the customer tele-
`phone, e.g.,'that the customer has gone off-hook, and
`information necessary to control telephone functions
`such as activate the status lamp, control the ringer, etc.
`Standards for the S/T-Interface have already been
`defined by CCITT; equipment supplied by different
`manufacturers which subscribe to those standards can
`be connected to network terminations as there will be
`no protocol incompatibilities. Standards for the U-inter-
`face, however, have not yet been defined. Special inte-
`grated circuits currently produced only by American
`Telephone and Telegraph (AT&T) and incorporated
`into AT&T equipment, are required for compatibility
`with the U-interface. Accordingly, whereas the princi-
`ples of the present invention have general applicability
`to ISDN network testing, the invention shall be de-
`scribed in an AT&T system operating environment.
`Thus, referring to FIG. 2, at the central office of the
`carrier (telephone company) is a solid state switch 20,
`provided by AT&T under the name 5ESS (TM) switch,
`for routing calls. As the SESS (TM) switch is well
`known, details will not be provided herein. An over-
`view of digital switches is given in Switching Systems,
`DataPro Research Corporation, Concepts and Tech-
`nologies, MT20-050-201 to 215, published by McGraw
`Hill Corporation (February 1988). Also at the central
`office is a conventional integrated services line unit
`(ISLU) 22, manufactured by AT&T, to interface cus-
`tomers with the SESS (TM) switch. The ISLU 22,
`which satisfies ISDN interface requirements,
`imple-
`ments a “2B+D” channel structure and is compatible
`with both the T- and 'U-interfaces. The ISLU 22 re-
`ceives up to 512 customer lines in 16 line groups, as
`shown in FIG. 3, and carries out duplex operation in
`two service groups at control cards CCO and CCl. Data
`handling is carried out by cards CDO and CD1, and
`metallic functions are performed by RV] and HV2
`which also contain line testing and high level service
`circuitry. Data cards CDO, CD1 are in circuit with the
`switch 20 over the standard peripheral interface data
`buses (PIDB) and directly connected PIDBs (DPIDB).
`The common control cards CCO, CCl receive instruc-
`tions from a central office switch processor (not shown)
`over the PICBs. The high voltage circuits HVl, HVl
`are connected on the standard metallic test bus (MTB)
`to enable any metallic functions such as ringing of cus-
`tomer lines and line testing to be performed. A complete
`block diagram summarizing the architecture of the stan-
`dard AT&T ISLU is shown in FIG. 4. The manner by
`which the AT&T ISLU processes customer calls origi-
`nating with or terminating at the ISLU, is well known
`in the industry and shall not be described in detail
`herein.
`Referring to FIG. 2, supplied to the ISLU 22 is the
`U-interface, used in ISDN, as well as the standard ana-
`
`Integrated services digital network (ISDN) is a rela-
`tively newly developed and emerging field of telecom-
`munications which integrates computer and communi-
`cations technologies to provide, world wide, a com-
`mon, all-digital network. This is based, in part, on stan-
`dardizing the structure of digital protocols developed
`by the International Telegraph and Telephone Consul-
`tative Committee (CCITT) so that, despite implementa-
`tion of multiple networks within national boundaries,
`from a user’s point of view there is a single, uniformly
`accessible, worldwide network capable of handling a
`broad range of telephone, data and other conventional
`and enhanced services.
`A complete description of the architecture of ISDN
`is beyond the scope of this specification. For details, and
`for an extensive bibliography of references on ISDN,
`see Stallings, ISDN, AN INTRODUCTION, Macmillan
`Publishing Company, 1989.
`As an overview of ISDN, and the interfaces therein,
`reference is made to FIG. 1 wherein a customer prem-
`ises is interconnected with a local exchange. At the
`customer premises an “intelligent” device such as a
`digital PBX, terminal controller or local area network
`(LAN) can be connected to an ISDN terminal TE, such
`as a voice or data terminal, which is connected, over an
`“RS-232-Interface",
`to a network termination NTl.
`Although not shown, non-ISDN terminals may be con-
`nected to a termination NT2 over the RS-232-Interface
`and another device termed a “terminal adapter”. The
`NT2 in turn is connected over an “S/T-Interface”,
`which is a four wire bus, to a termination NTl that
`performs functions such as signal conversion and main-
`tenance of the electrical characteristics of the loop. The.
`NTl thus is a termination between customer and tele-
`phone company equipment.
`At the local loop, a two-wire bus, termed the “U-
`interface”, or “loop” interconnects network termina-
`tion NTl and a loop termination LT at the central of-
`fice. Finally, the “V-interface” is a bus between the
`local loop at the carrier end and exchange switching
`equipment. Details of this architecture are provided in
`Integrated Services Digital Networks (ISDN): An Over-
`view, DataPro Research, Concepts & Technologies,
`MT20-365-101 to 110, published by McGraw Hill In-
`corporated (December, 1988).
`
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`3
`log interface. Data on the U-interface is optionally mon-
`itored by a U-interface monitoring system (UIMS) 24,
`manufactured by AT&T, interposed in series between
`the ISLU 22 and a network termination NTl associated
`with the telephone or terminal of an ISDN customer.
`The purpose of the UIMS 24 is to monitor the protocol
`of control data on the U-interface,
`to determine
`whether the ISDN line of a customer is functioning
`properly. The UIMS separates the B1-, B2-, and D-
`channel bit streams (2B+D) on the U-interface, and
`presents this data to a protocol analyzer 30 that typi-
`cally is transported to the central office by service per-
`sonnel.
`The protocol analyzer 30, which is conventional,
`carries out ISDN protocol decoding to enable both
`B-channel and D-channel traffic to be tested. However,
`it is only the D-channel traffic that ordinarily is tested,
`as it is only the D-channel that contains the supervisory
`data necessary to assess the operation of a customer
`ISDN line, including information to control operations
`such as feature activation, lamp operation, ringing, dial-
`ing and supervision. In this regard, a protocol analyzer
`is analogous to a “butt-set” currently used to test analog
`telephone lines.
`However, implementing efficient protocol analysis in
`an ISDN network having a large number of nodes poses
`particular problems. The prior art has sought to test
`ISDN networks by installing dedicated protocol analy-
`zers to monitor the S/T-Interface; this is costly and time
`consuming as it requires a field visit on every trouble
`call. Furthermore, service personnel employed by the
`telephone company cannot properly access the cus-
`tomer side of the S/T-Interface.
`Protocol monitoring and analysis are better per-
`formed at the central office. The test system shown in
`FIG. 2 implements the UIMS to monitor the customer
`ISDN lines at each central office. However, this also is
`disadvantageous because it still requires dispatching of
`service personnel
`to those central offices which are
`unmanned, as is necessary to physically insert a plug to
`interconnect the UIMS and the main distribution frame
`of the ISLU. Such a procedure is not easily imple-
`mented.
`
`One particular system implemented in the prior art
`multiplexes the D-channel data obtained from the
`UIMS up to 56 kilobits per second or 64 kilobits per
`second, using a Remote Access Test Device (TM),
`manufactured by Tekelec, Calabasas, Calif., with input
`to one B-channel of an on-site standard 750X modem, to
`be transmitted to a central
`test facility for protocol
`analysis of a line under test. However, this technique
`requires that service personnel be dispatched to the
`central office to make the connection between the
`UIMS and main distribution frame, to access the U-
`interface bus.
`In view of the above, it would be desirable to provide
`a system wherein the ISDN lines could be tested at the
`central test facility without requiring service personnel
`to be dispatched to initiate the testing. It would also be
`desirable to provide the data received from the UIMS
`and/or data generated from the protocol analyzer indic-
`ative of the test results directly to remote locations from
`the central office under test.
`
`'
`
`DISCLOSURE OF THE INVENTION
`
`65
`
`Accordingly, one object of the invention is to test
`customer ISDN lines and report data indicative of the
`test results to remote locations without the necessity of
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`5,189,663
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`dispatching personnel to a customer site or central of-
`fice.
`Another object is to provide a hard copy of the data
`at the remote location.
`‘
`Another object of the invention is to provide a
`method of and system for testing and reporting of cus-
`tomer ISDN line conditions at an ISDN. test facility
`remote from a central office serving the lines.
`Another object is to carry out remote and unattended
`testing and reporting of customer ISDN line conditions
`using equipment that is low in cost and easily imple-
`mented.
`
`A further object of the invention is to analyze proto-
`col of D-channel data on the U-channel bus of customer
`ISDN lines at a central office serving the lines and to
`automatically transmit data indicative of the analysis to
`remote locations, without the necessity to dispatch ser-
`vice personnel to the office.
`Another object is to provide unattended protocol
`analysis of ISDN channel data at a central office serving
`selected customer ISDN lines and direct reporting of
`analysis data to remote locations.
`The above and other objects of the invention are
`satisfied, at least in part, by providing, at a central office
`serving customer ISDN lines to be tested, circuitry for
`accessing at least the D-channel data of a selected cus-
`tomer ISDN line, and a first computer programmed to
`provide protocol analysis. The at least D-channel data is
`applied to the first computer for protocol analysis. The
`first computer is coupled to a report communication
`line. A second computer at a test facility remote from
`the central office controls the operation of the first
`computer to carry out the protocol analysis and to se-
`lectively supply data to the report communication line.
`A hard copy report can be generated at a remote loca-
`tion, if desired, by a facsimile coupled to the report
`communication line and adapted to receive the data
`supplied to the report communication line. The data
`Accordingly,
`it
`is not necessary to dispatch service
`personnel to the central office to perform the protocol
`analysis necessary to test selected ISDN lines.
`In accordance with a preferred embodiment of the
`invention, the at least D-channel data is obtained from
`the U-interface bus at the central office. The U-bus
`preferably is accessed at the conventional integrated
`services line unit (ISLU) at the central office using the
`“line card sparing” feature of the ISLU. This is carried
`out by permanently connecting a conventional U-inter-
`face monitoring system (UIMS) to one of the sparing
`cards provided with the ISLU and selectively rerouting
`the sparing card to the line card associated with a cus-
`tomer ISDN line to be tested. The output of the UIMS
`is applied to the first computer, at the central office,
`which is programmed to perform protocol analysis of
`the at least D-channel data and is controlled by the
`second computer at the remote facility. In so doing, the
`protocol of D-channel data of any customer ISDN line
`can be tested without dispatching service personnel to
`the central office. Data indicative of the result of the
`protocol analysis is reported to remote locations via the
`report communication line. The raw data used to per-
`form the protocol analysis, i.e., the D-channel data, can
`also protocol analysis, i.e., the D-channel data, can also
`be transmitted by the first computer to remote locations
`via the report communication line if so desired.
`In accordance with one aspect of the invention, the
`UIMS or other D-channel data supplying means is en-
`abled in response to a remote control signal transmitted
`
`

`

`5
`from the remote test facility. This prevents “collisions"
`that would otherwise tend to occur between ISDN line
`testing as described herein, and maintenance that
`is
`carried out by routine exercise (Rex) by the central
`office. Preferably, the remote control signal is applied
`to a relay that, when enabled, applies operating power
`to the D-channel data supplying means.
`‘
`In accordance with another aspect, the central office
`may contain a plurality of ISLU’s for interconnecting a
`large number of ISDN lines at the central office to the
`conventional solid state switch provided by the tele-
`phone company. To provide multiplexing among the
`ISLU’s so as to access a selected cu‘stomer ISDN line
`
`for testing, circuitry at the central office is responsive to
`a remote control signal transmitted from the remote test
`facility for selecting one of the ISLU’s at a time for
`routing of a “U” interface therein to the UIMS.
`In accordance with a further aspect of the invention,
`an apparatus for remote and unattended testing of an
`integrated services digital network (ISDN) at a central
`office comprises:
`(I) ISDN testing equipment at the central office in-
`eluding
`(a) a monitor for accessing a U-interface bus of a
`selected customer ISDN line at the central office,
`(b) a circuit path established for obtaining from the
`U-interface bus at least D-channel data on a selected
`customer ISDN line, and
`(c) a protocol analyzer for providing protocol analy-
`sis of said at least D-channel data;
`(d) a report mechanism for transmitting data to re-
`mote locations from the central office;
`(II) an ISDN testing facility remote from the central
`office; and
`(III) remote control circuitry located at the ISDN
`testing facility for controlling the ISDN testing equip-
`ment at the central office.
`Preferably, the circuit path (b) is established by rer-
`outing a sparing card of the standard ISLU at the cen-
`tral office to the line card slot associated with the ISDN
`line to be tested. The monitor is connected between the
`
`sparing card and the network terminal of the customer,
`and supplies at least D-channel data obtained from the
`U—bus to the protocol analyzer.
`In the preferred embodiment, the protocol analyzer is
`implemented by a personal computer programmed to
`carry out protocol analysis. The personal computer at
`the central office is controlled on a dial up line by an—
`other computer at the remote test facility.
`In accordance with the method of this invention, the
`following steps are carried out. At the central office, the
`method provides:
`(a) selecting a customer ISDN line;
`(b) accessing a U-interface bus of a selected customer
`ISDN line;
`(c) monitoring at least D-channel data on said se-
`lected ISDN line;
`(d) analyzing the protocol of the at least D-channel
`data; and
`(e) selectively supplying data to a report communica-
`tion line.
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`The following additional steps are performed at an
`ISDN test facility remote from the central office:
`(e) generating control signals for controlling steps
`(b)—(e); and
`(f) transmitting the control signals to the central of-
`fice.
`
`65
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`5,189,663
`
`6
`The method preferably is practiced in the environ-
`ment of the central office serving the customer ISDN
`lines to be tested and whereat are located at least one
`
`integrated services line unit (ISLU) having a plurality
`of line cards positionable in line card “slots" in circuit
`with corresponding U-interfaces each containing ISDN
`B- and D-channel data. At least one of the line card slots
`
`therein is available as a sparing slot to receive a line card
`configured to be a sparing card, reroutable by the stan-
`dard Metallic Access Network of the ISLU to replace
`the selected line card to be tested. The method more
`
`particularly comprises the steps of:
`at the central office
`
`(a) selecting an ISDN line to be tested,
`(b) accessing a U-interface bus of a selected ISDN
`line by routing the selected line card to the sparing slot
`containing the sparing card,
`(c) monitoring at least D-channel data at the output of
`the sparing card, and
`(d) analyzing the protocol of at least the D-channel
`data;
`(e) selectively supplying data to a report communica-
`tion line; and
`at an ISDN test facility remote from the central office
`(i) transmitting a first control signal to the central
`office to control step (b), and
`(g) using a computer, transmitting second and third
`control signal to the central office for controlling steps
`(d) and (e), respectively.
`Still other objects and advantages of the present in-
`vention will become readily apparent to those skilled in
`this art from the following detailed description, wherein
`only the preferred embodiment of the invention is
`shown and described, simply by way of illustration of
`the best mode contemplated of carrying out the inven-
`tion. As will be realized, the invention is capable of
`other and different embodiments, and its several details
`are capable of modifications in various obvious respects,
`all without departing from the invention. Accordingly,
`the drawing and description are to be regarded as illus-
`trative in nature, and not as restrictive.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`FIG. 1 is a simplified circuit diagram of an integrated
`services digital network.
`FIG. 2 is a diagram of the central office circuitry to
`support ISDN.
`FIG. 3 is a simplified diagram of an integrated ser-
`vices line unit (ISLU).
`FIG. 4 is a more detailed diagram of the ISLU.
`FIG. 5 is a circuit diagram showing the line card
`sparing feature of the ISLU.
`FIG. 6 is a diagram of an ISDN testing system in
`accordance with one embodiment of the invention.
`FIG. 7 is a wiring diagram showing how the option
`plug at the ISLU is modified to be accessed by the
`UIMS.
`
`FIG. 8 is a diagram of an ISDN testing system in
`accordance with a second embodiment of the invention,
`wherein the UIMS is powered only during an ISDN
`line test.
`
`FIG. 9 is a diagram of an ISDN testing system in
`accordance with a third embodiment, wherein multiple
`ISLU’s are selected for access, one at a time, by a multi-
`plexer.
`
`

`

`7
`
`BEST MODE FOR PRACTICING THE
`INVENTION
`
`5,189,663
`
`The invention is based in part on the realization that
`the U-interface bus at the central office can be accessed
`through the line card sparing feature of the conven-
`tional ISLU. This feature enables any of the ISLU line
`cards to be rerouted to a sparing slot whereat a line
`sparing card resides and the U-interface on the sparing ’
`10
`bus can be accessed.
`
`To more fully appreciate the principles of this inven-
`tion, the line sparing feature of the conventional AT&T
`ISLU will be described. In conventional practice, ISLU
`architecture provides the metallic access necessary for a
`spare line circuit to be switched in the place of a faulty
`line circuit; this is sometimes referred to as a “hot spare”
`capability. A fault may be detected on a “per call” basis
`or on a routine basis through diagnostic testing of ana-
`log lines by a conventional diagnostic exercise provided
`by AT&T under the name “REX”. Per-call tests are
`carried out before terminating a call or when an origina-
`tion is detected. In instances when faults cause the ana-
`log line card to be unable to detect originations, detec-
`tion of the fault is made only during full diagnostic
`testing by REX on a routine basis. Once a line card is
`determined to be faulty, it is bypassed by a spare line
`card resident at the ISLU for that purpose, i.e., it is
`“spared”.
`_
`More specifically, the conventional ISLU contains
`512 line cards, each located in a line card slot, to inter-
`connect the tip and ring of a customer line and the
`central office switch. Among the 512 line cards are at
`least one, and probably two, line cards that are config-
`ured, using jumpers, as a spare (sometimes termed
`“sparing”) line card provided to electrically bypass and
`replace a customer line card determined to be faulty.
`This is carried out through a switching array, termed a
`“Metallic Access Network” (MAN) by AT&T'that is
`standard in the conventional ISLU.
`Referring to FIG. 5, each line card 40 contains a pair
`of metal leads 42a, 42b that form a portion of the U-
`interface bus interconnecting the tip and ring of a cus-
`tomer line and a line interface 44 of the central office
`switch. A first pair of relay contacts 430, 43b is con-
`nected in the U-interface 42a, 42b to selectively isolate
`the corresponding customer ISDN line from the central
`office switch. Also connected to the lines 42a, 42b is a
`- line group bus 48, containing a second pair of relay
`contacts 460, 46b. The line group bus 48 is connected to
`one port of the Metallic Access Network 50. At the
`other port of the Metallic Access Network 50 is con-
`nected a spare, or option, plug 52, jumpered to form the
`wiring configuration shown. Another line card, config-
`ured as a sparing line card 54, is connected to the spare
`plug 52 at a “sparing slot” in the plug.
`Another pair of leads is connected to the U-interface
`leads 42a, 42b through relay contacts, or “crosspoints”,
`45a, b, c, d, to be configured for particular applications.
`All relay contacts are independently controllable by the
`switch processor 55.
`In normal line card operation, relay contacts 430 and
`43b are closed, so that a loop including the tip and ring
`leads of a customer line is formed between the customer
`terminal and the central office switch.
`
`When the line card sparing feature is implemented,
`the relay contacts 43a, 43b on card 40 are opened, to
`interrupt the loop between the customer terminal and
`the central office switch. With contacts 43a, 43b of line
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`8
`card 40 open, the relay contacts 46a, 46b of line group
`bus 48 are closed, and a circuit path between spare plug
`52 and line card 40 is established through the Metallic
`Access Network 50. This is‘controlled by the central
`office switch processor 55, which may be a 3B20 com-
`puter. The processor 55 in turn is controlled by instruc-
`tions sent over a dedicated line by personnel operating
`a standard AT&T Trunk Line Work station from a
`remote service facility. The Metallic Access Network
`50 in this manner is capable of interconnecting the spar-
`ing line card 54 to any one of the remaining line cards,
`determined to be defective, by service personnel at the
`remote facility.
`In accordance with the invention, the tip and ring of
`the U-interface, routed to the sparing card 54 through
`the MAN 50 and spare plug 52, is connected in series
`with a UIMS 24, which extracts the B- and D-channel
`data therefrom. Accordingly, as a result of circuit rout-
`ing of the tip and ring of the selected customer line by
`the Metallic Access Network 50, the U-interface bus of
`any selected customer line is made to be available to the
`sparing line card 54.
`With the above background in mind, reference is now
`made to FIG. 6, wherein a system for remote and unat-
`tended testing of customer ISDN lines comprises an
`ISDN test facility 60, remote from a central office 62,
`serving ISDN lines to be tested. At the facility 60 are a
`personal computer 64, programmed to carry out com-
`munications with another personal computer 66 at the
`central office 62. Communications is established be-
`tween the two computers 64 and 66 using master-slave
`communications software, such as pcAnywhere (TM),
`over a dial-up ISDN line 68. pcAnywhere (TM), manu-
`factured by Dynamic Microprocessor Associates, Inc.,
`enables the operator at the remote facility 60 to control
`all the operations of computer 66. Although other com-
`munication programs can be used for this purpose, one
`particularly useful attribute of pcAnywhere (TM) is
`that it enables the functions of computer 66 at the cen-
`tral office to be controlled from the keyboard of com-
`puter 64 at the remote test facility, and that the monitor
`display at computer 64 is a simulation of the monitor
`display at computer 66.
`The computer 66 is provided with a modem and
`communications software, for example Complete Fax
`9600 manufactured by The Complete PC, Inc., to en-
`able data to be transmitted to any desired remote loca-
`tion over a report communication line 69. Thus, a com-
`mand can be sent from computer 64 to computer 66 via
`the line 68 to initiate reporting of data, either data indic-
`ative of the protocol analysis performed and/or the raw
`data used to perform the protocol analysis, directly
`from computer 66 to a remote receiving facility 73.
`A receiving device 71 is provided at the remote re-
`ceiving facility 73 to receive the data transmitted by the
`computer 66 over the report communication line 69.
`Preferably, the receiving device 71 is a facsimile ma-
`chine adapted to receive data supplied to the report
`communication line 69 by the computer 66 and generate
`a hard copy report. For example, the screen display of
`the computer 66 is transmitted to and reproduced by the
`facsimile machine generating a hard copy report from
`which repair work orders can be generated. Other types
`of devices, however, may be employed at the receiving
`facility such as a computer and printer.
`Also at the test facility 60 is the standard AT&T
`Trunk Line Work station 70, or an equivalent, that is
`connected, through a dedicated line 72, to the central
`
`

`

`9
`switch processor 55 which controls the line card spar-
`ing feature of the ISLU 20.
`Referring to FIG. 7, the spare plug 52 in the ISLU 20
`is modified to receive, in series, the UIMS 24 to obtain
`from the U-interface bus associated with the selected
`customer line at least the D-channel data thereon, in
`other words, the UIMS 24 monitors the D-channel data
`and possibly the B-channel data as well. Although both
`B- and D- channel data are available at the U-interface
`bus, it is only the D-channel data that is of interest for
`the purpose of testing the operation of a customer
`ISDN line.
`
`The D-channel data, monitored by UIMS 24, is ap-
`plied over a serial bus 74, in RS 232 or other suitable
`format, to the serial port of computer 66 for protocol
`analysis. One example of a program for carrying out
`protocol analysis of ISDN data is “LMl Protocol Ana—
`lyzer” (TM), provided by Progressive Computing. The
`LMl (TM) is in the form of a circuit board, plugged
`into one of the slots of computer 66, that controls the
`computer to be menu driven and to be automatically
`configured to carry out decode analysis of ISDN proto-
`cols. Although LMl (TM) is preferred, other equiva-
`lent computer programming to carry out this function
`can be used. Furthermore, it is within the scope of this
`invention to use any type of dedicated protocol analy-
`zer, rather than a personal computer programmed to
`provide protocol analysis, for this purpose.
`The operation of the system for testing a selected
`customer ISDN line is as follows. Recall that ISLU 22
`contains 512 line cards, and assume that one of the cards
`(e.g., at slot 15) is configured to function as a sparing
`card. Assu