GB2354906A

GB2354906A - Line testing arrangement

Info

Publication number: GB2354906A
Application number: GB0011695A
Authority: GB
Inventors: Hiroyuki Asano; Shuichi Nakagawa
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 1999-08-30
Filing date: 2000-05-15
Publication date: 2001-04-04
Anticipated expiration: 2020-05-15
Also published as: CN1286560A; GB2354906B; JP2001069243A; GB0011695D0

Abstract

An arrangement for testing an ISDN line only performs a test if it is determined that a network terminal unit 2a, 2b, 2c is not in communication with a subscriber transmission device 3. The test may comprise determining electrical characteristics of the line or sending a pattern of test data to the network terminal unit which is subsequently looped back to the subscriber transmission device.

Description

2354906 SUBSCRIBER TRANSMISSION DEVICES The present invention relates to -

subscriber transmission devices, and more particularly, to --subscriber transmission devices arranged between - exchange and network terminal units for relaying information therebetween according to a predetermined protocol.

With recent popularization. of the Internet, ISDN (Integrated Service Digital Network)-BRA (Basic Rate Access) etc., for example, have been spreading to ordinary homes.

If, in such ISDN-BRA, a communication fault occurs, it is necessary that a subscriber test be conducted to determine proper/improper functioning of subscriber lines etc., as in the case of' PSTN (Public Switched Telephone Network), in order to specify the location where the f ault has occurred. 20 At present, there is no established subscriber test method for ISDN-BRA, and therefore, electrical characteristics of subscriber lines are measured to locate a fault, as in the case of PSTN. In ISDN-BRA, however, since network terminal units are connected at subscribers' homes and thus the line conditions are different, a problem arises in that it is difficult to directly use a method similar to that adopted 2 in PSTN.

An error occurring in subscriber lines etc. may be measured using a measuring device to locate a fault. However, each time a fault occurs, the measuring device needs to be connected at a predetermined location, thus consuming labor, and such labor-consuming work requires a lot of time before recovery.

Further, in the case of PSTN, line control is performed by means of a signal indicative of whether the loop is open or closed, and it is therefore relatively easy to determine whether a call is in progress or not. By contrast, in the case of ISDN- BRA, the contents of a message need to be decoded to determine whether communication is in progress or not, and thus it is not easy to detect the communication state. If test is conducted without regard to the communication state, ongoing communication is disrupted.

The present invention was created in view of the above circumstances. It is desirable to provide a subscriber transmission device capable of applying a subscriber test to, for example, ISDN-BRA etc.

Accordina to one embodiment -of the present invention there is provided a subscriber device arranqed between an exchanqe and network terminal units for relaying information therebetween according to a predetermined protocol. The subscriber transmission device comprises target specifying 3 means f or specifying a predetermined network terminal unit which is a target of a test, ongoing communication detecting means for detecting the presence/absence of ongoing communication by the predetermined network terminal unit specified by the target specifying means, and testing means for testing a characteristic related to a state of communication with the Aetwork terminal unit specified by the target specifying means, in accordance with a result of the detection by the ongoing communication detecting means.

Apparatus features may be provided with the method aspect and vice versa.

Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:FIG. 1 is a diagram illustrating a principle of operation according to an embodiment of the present invention; FIG. 2 Is a diagram showing An example of a configuration according to an embodiment of the present invention; FIG. 3 is a diagram showing an example of an arrangement of a network terminal unit appearing in FIG. 2; FIG. 4 Is a diagram showing, by way of example, details of an arrangement of a subscriber transmission device appearing, in FIG. 2; FIG. 5 is a flowchart illustrating an example of a process executed in the embodiment shown in FIG. 4; FIG. 6 shows an example of a table which is referred to when judging test results; FIG. 7 is a flowchart illustrating details of an 5 'KELECTRICAL TEST" shown in FIG. 5; FIG. 8 shows a table which is referred to when determining proper/improper functioning of a subscriber line in accordance with measurement results of the electrical test shown in FIG. 7; FIG. 9 is a flowchart illustrating details of a LOOPBACK TEST OF NETWORK TERMINAL UNIT" shown in FIG. 5; and FIG. 10 is a flowchart illustrating details of a "LOOPBACK TEST OF SUBSCRIBER CIRCUIT shown in FIG. 5.

Fig. 1 illustrates a principle of operation f according to an embodiment of the present invention.

In the figure, subscriber terminals la to lc each comprise a telephone, a modem or the like, for example. The subscriber terminals convert a primary signal such as a speech signal to a digital signal to be supplied to respective network terminal units 2a to 2c, and also convert a digital signal supplied thereto from the respective network..terminal units 2a to 2c to a corresponding primary signal to be output therefrom.

Each of the network terminal units 2a to 2c serves as an adapter for exchanging information with a subscriber transmission device 3 by means of digital signal.

The subscriber transmission device 3 is arranged corresponding to the multiple network terminal units 2a to 2c, and serves as an adapter for exchanging informatlon with these units by means of digital signal.

The subscriber transmission device 3 comprises target specifying means 3a, ongoing communication detecting means 3b, and testing means 3c.

The target specifying means 3a specifies a predetermined network terminal unit which is a target of test.

The ongoing conununication detecting means 3b detects the presence/absence of then ongoing communication of the predetermined network terminal unit specified by the target specifying means 3a.

If the network terminal unit specified by the target specifying means 3a. is then not performing communication, the testing means 3c conducts a test on the target network terminal unit and a subscribe r line associated therewith.

FIG. 1 shows only those parts of the subscriber transmission device 3 which are relevant to the present invention, and other parts of the device are omitted.

An exchange 4 carries. out a process for establishing/releasing line connection with a desired 6 destination of communication.

The operation of the embodiment described above will be now explained.

When the subscriber transmission device 3 is input with a telephone number or the. like of a network terminal unit which is a target of test, the target specifying means 3a specifies the corresponding network terminal unit by making reference, for example, to a database etc.

The database may be provided independently (In an external device), and the external database may be searched for information such as an ID of a network temminal unit corresponding to the telephone number so that the network terminal unit corresponding to the obtained ID may be specified by the target specifying means 3a.

After the target network terminal unit is specified, the ongoing communication detecting means 3b determines whether or not the target network terminal unit is currently performing communication.

Assuming that the network terminal unit 2a, for example, is specified by the target specifying means 3a as a target of test, the ongoing communication detecting means 3b checks for a message exchanged with the network terminal unit 2a to determine whether or not communication is in progress, and notifies the testing means 3c of the result of determination.

If the target network:terminal unit is not currently performing communication, the testing means 3c 7 tests electrical characteristics of the subscriber line connecting the network terminal unit and the subscriber transmission device 3, and also causes a subscriber circuit, not shown, built in the subscriber transmission device 3 or the target network texminal unit to reflect back data, to thereby measure an error occurrence rate. By making reference to the measurement results, It is possible to specify the location where a fault has occurred.

In this example, the network terminal unit 2a is the target of test, and therefore, the subscriber transmission device 3 first measures electrical characteristics (e.g. electrical resistance, capacitance, voltage, etc.) of the subscriber line connected to the network terminal unit 2a.

Subsequently, the subscriber transmission device 3 makes a request for loopback of transmit data to the network terminal unit 2a, and then transmission data with a predetermined pattern Looped back or reflected data is checked to detect the rate of error occurrence between the subscriber transmission device 3 and the network terminal unit 2a.

The subscriber transmission device 3 then makes a loopback request to the subscriber circuit built therein, and transmits data with a predetermined pattern. Looped back data is checked to detect the rate of occurrence of Internal error in the subscriber transmission device 3.

Finally, the subscriber transmission device 3 estimates a location of f ault based on a synthetic judgment of the Inf ormation obtained by the tests, and outputs the result of estimation to a display device or the like, not shown, to be displayed thereon.

As described above, in the subscriber transmission device 3 according to the present arnbodiment, a target of test is specified, and:after it is ascertained that the target is not currently performing communication, various tests are conducted to estimate a location of fault, whereby tests can be conducted without disrupting ongoing communication of the target subscriber.

Also, not only the time and labor required to connect a measuring device can be omitted but a series of processes is automatically executed, so that the burden on the operator who performs testing can be lessened.

An exemplary conf igurati-on according to an embodiment of the present invention will be now described.

FIG. 2 Illustrates the configuration according to an embodiment of the present invention. In the f igure, subscriber terminals 10a to 10c, each of which comprises a telephone, a modem, a facsimile machine or the like, convert a primary signal, such as a speech signal or image signal, to a digital signal to be supplied to respective network terminal units 20a to 20c, and also convert a digital signal supplied thereto from the respective network terminal units 20a to 20c to a corresponding primary signal to be output therefrom.

The network terminal units 20a to 20c are each an adapter for exchanging information by means of digital signal with a subscriber transmission device 30 via respective subscriber lines 25a to 25c.

FIG. 3 Illustrates the arrangement of the network terminal unit 20, by way of example. The figure shows only those parts of the unit: which are relevant to the present invention.

in FIG. 3, a detecting section 21 detects Information requesting loopback when such information is transmitted from the subscriber transmission device 30. As the information requesting loopback, a predetermined bit in a packet transmitted from the subscriber transmission device 30 may be used.

When the- information requesting loopback is detected by the detecting section 21, a loopback section 22 reflects the data transmitted thereto from the subscriber transmission device 30 back to the same device.

The subscriber transmission device 30 is arr anged corresponding to the multiple network terminal units 20a to 20c and serves as an adapter for exchanging information with these units by means of digital signal. Also, the subscriber transmission device 30 converts an optical signal transmitted thereto from an exchange 40 to a 2B1Q (2 binary, 1 quaternary) signal by photoelectric conversion, and converts an internal signal, which.. is 2BlQ signal, to a corresponding optical signal to be transmitted to the exchange 40.

FIG. 4 is a block diagram showing details of the arrangement of the subscriber transmission device 30, by way of example.

In the figure, an I/F (Interface) 30a converts an optical signal transmitted thereto from the exchange 40 to a corresponding 2B1Q signal by photoelectric conversion, and also converts an internal 2BIQ signal to a corresponding optical signal to be transmitted to the exchange 40.

A cross-connect section 30b accommodates a plurality of transmission paths for connection to other transmission paths, and permits low-speed line channels to connect to/diverge Into desired transmission paths via desired transmission paths.

A subscriber circuit 30c, which is provided for each subscriber, reflects data output from the cross-connect section 30b back to the same section when requested by a system control section 30h. Also, the subscriber circuit sets a predetermined control bit ON when loopback is to be performed with respect to the network terminal unit.

When a subscriber line testing section 30g performs testing of the subscriber line 25, a switch 30d changes over the connection of the subscriber line 25 from the subscriber circuit 30c to the subscriber line testing section 30g.

An error measuring sect:Lon.30e comprises a pattern generating section 31 and an error detecting section 32.

When a loopback test is conducted, the pattern generating section 31 generates data having a predetermined pattern, and the error detecting section 32 detects an error occurrence rate of the same data looped back thereto.

A protocol processing section 30f performs communication control, such as call connection control, fault processing, speech path control, subscriber control, etc., in accordance with the ITU-T recommended d.965 (V5.2) protocol, for example.

The subscriber line testing section 30g, which comprises a voltage detecting section 33, a resIstance detecting section 34 and a capacitance detecting section 35, measures the voltage, resistance and capacitance of the subscriber line 25 and notifies the system control section 30h of the measurement results.

The system control section 30h. controls the individual sections of the device and, If requested to test a certain network terminal unit from a subscriber test console 38, conducts tests in predetermined sequence to locate a fault.

The subscriber test console 38 is a workstation or the like, for example, and when Input with the telephone number etc. of a target of test, it ref ers to a database contained therein to acquire the ID of a corresponding network terminal unit, and supplies the acquired ID to the system control section 30h to request testing of the target network terminal unit.

The operation of the embodiment described above will be now explained.

FIG. 5 is a flowchart illustrating an example of a process executed in the embodiment shown in FIG. 4. Upon 5 start of the process, the following steps are executed.

[Sl] The subscriber test console 38 is input with the subscriber telephone:number of a target of test.

[S2] The subscriber test console 38 refers to a database or the like stored In a storage device etc. built therein, to acquire the ID of a network terminal unit corresponding to the input subscriber telephone number.

[S31 Looking up the acquired ID, the subscriber test console 38 determines whether or not the service (subscription service) that the target subscriber subscribes to is ISDN. If the subscribed service Is ISDN, the flow proceeds to Step S4; if not (If, for example, the subscribed.service is PSTN), the process Is ended.

In the case where the service to which the subscriber subscribes is PSTN, a subscriber line test may be conducted by the subscriber line testing section 30g, for example.

[S4] The subscriber test console 38 notifies the system control section 30h of the acquired ID, to request testing.

[S5] The system control section 30h supplies the ID to the protocol processing section 30f, to request the same to make a check (busy check) as to whether or not the 13 corresponding network terminal unit is currently performing communication.

S61 If as a result of the inquiry made with respect to the protocol processing section 30f, It is found that the target network terminal unit is currently performing communication, the system control section 30h repeatedly executes Step S6; If not, the flow proceeds to Step S7.

[S7] The system control section 30h changes over the connection of the switch 30d to the subscriber line testing section 30g side, and also requests the subscriber line testing section 30g.to conduct a subscriber line test.

Consequently, the subscriber line testing section 30g measures electrical characteristics of the subscriber line according to a process described later with reference to FIG. 7.

[S8] The system control section 30h conducts a loopback test of the target network terminal unit.

Details of this process will be described later with reference to FIG. 9.

[S91 The system control section 30h conducts a loopback test of the target subscriber circuit.

Details of this process will be described later with reference to FIG. 10.

[SIO] Making reference to the results of the electrical test, the loopback test of the network terminal unit, and the loopback test of the subscriber circuit, the system control section 30h determines the location where fault has occurred.

FIG. 6 shows the relationship between test results and locations of f ault. If the test results are all "OKw as shown In the f irst item in the f Igure, the subscriber transmission device 30 Is normal, and fault has probably occurred In some other equipment (e.g., subscriber equipment, the exchange 40, or the line between the exchange 40 and the subscriber transmission device 30).

The second item shows the case where the result of the electrical test alone is 'NGw, In which case fault has probably occurred in the subscriber line.

The third item shows the case where the results of the electrical test and the loopback test of the network terminal unit are both "NGw, and in this case fault has probably occurred in the subscriber line and in the network terminal unit.

The fourth Item shows the case"where the result of the loopback test of the network terminal unit alone is "NGff, In which case fault has probably occurred in the network terminal unit.

The f if th item shows the case where the result of the loopback test of the subscriber circuit 30c is 'NGff, and In this case, it is judged that f ault has probably occurred In the subscriber circuit 30c, whatever the result of the loopback t ' est of the network terminal unit may be.

[S111 The system control section 30h causes the subscriber test console 38 to display the test results and the judgment made in Step SIO, whereupon the process is ended.

According to the process described above, the telephone number of a target subscriber has only to be input from the subscriber test console 38, whereupon the target of test is automatically specified and the tests are conducted while communication is not in progress, so that the burden on the operator who performs testing can be lightened.

Further, not only a series of tests is automatically conducted but the location of fault is estimated from the test results and is displayed, whereby the time consumed before recovery from fault can be shortened.

Referring now to FIG. 7, the "ELECTRICAL TEST" shown in Step S7 of FIG. 5 will be described in detail. Upon start of the process shown in the flowchart, the following steps are executed.

[S201 The voltage detecting section 33 of the subscriber line testing section 30g measures DC (Direct Current) voltages A-B, A-G and B-G of the subscriber line 25 Here, A and B denote the two signal lines, respectively,. and G denotes the ground. Accordingly, A-B denotes a value derived between the two signal lines, and A- G and B-G denote values derived between corresponding ones of the two signal lines and the ground.

[S211 The voltage detecting section 33 measures AC (Alternating Current) voltages A-B, A-G and B-G of the subscriber line 25.

[S22] If any of the AC voltages detected in Step S21 is higher than 8 V, the system control section 30h ends the process in order to prevent the subscriber line testing section 309 from developing trouble due to overvoltage; If not, the flow proceeds to Step S23.

[S231 If the absolute value of the DC voltage A-G, detected In Step S20, Is lower than 8 V, the system control section 30h executes the subsequent Step S24; if not, the process is ended to prevent the subscriber line testing section 30g from developing trouble due to overvoltage.

[S24] If the absolute value of the DC voltage B-G, detected In Step S20, is lower than 8 V, the system control section 30h executes the subsequent Step S25; if not, the process is ended to prevent the subscriber line testing section 30g from developing trouble due to overvoltage.

CS25] The resistance detecting section 34 of the subscriber line testing section 30g measures resistance values A-G and B-G.

[S26] The capacitance detecting section 35 of the subscriber line testing section 30g measures capacitance values A-G and B-G.

[S27] If the absolute value of the DC voltage A-B detected in Step S20 is higher than 8 V, the system control section 30h ends the process in.. order to prevent the subscriber line testing section 30g from developing trouble due to overvoltage; if not, the f low proceeds to Step S28.

[S28] The capacitance detecting section 35 of the subscriber line testing section 30g measures a capacitance value A-B.

The results of the aforementioned measurements are notified to the system control section 30h, which then determines proper/improper functioning of the subscriber line.by making reference to a table shown In FIG. 8. FIG. 8 Illustrates how judgment is made In the case of ISDN as well as PSTN.

As shown in FIG. 8, the subscriber line Is judged to be normal if the test results are outside all the ranges shown in the second through seventh check items.

The second item "Abnormal Insulation" (abnormality In insulation) applies when either RAG (resistance A-G) or RBG (resistance B-G) f alls within a range of 6 KQ to 60 KQ. The third item "Line break' (line disconnection) applies when RAB (resistance A-B) Is higher than 6 KO or CAB (capacitance A-B) is lower than 0.4 pF. 20 The fourth item 'Mixture line' (short circuit) applies when RAB is lower than 1. 5 KQ. The f ifth item 'mTouch to earthn (grounding) applies when RAG or RBG f alls; within a range of 0 KQ to 6 KQ. 25 The sixth item Llne carry voltagew (mixture of power: e.g., contact with commercial -power) applies when any of VAB (voltage A-B), VAG (voltage A-G) and VBG (voltage B- G) Is higher than 4 V. The seventh item "Electric leakageff (leak of electricity) applies when CAG (capacitance A-G) or CBG (capacitance B-G) is higher than 0.5 pF. 5 When none of the above items is applicable, the subscriber line Is judged to be normal. Ref erring now. to FIG. 9, the process "LOOPBACK TEST OF NETWORK TERMINAL UNITN shown in Step S8 of FIG. 5 will be described in detail. Upon start of the process shown In the flowchart, the following steps are executed.

[S30] The system control section 30h controls the subscriber circuit 30c and causes the same to transmit data in which a predetermined control bit (control bit requesting loopback) Is set ON, to the network terminal unit.

As a result, the detecting section 21, shown in FIG. 3, of the corresponding network terminal unit detects the ON state of the control bit, and notifies the loopback section 22 of the detected state. In accordance with the notification from the detecting section 21, the loopback section 22 reflects data transmitted from the subscriber transmission device 30 back to the same device. [S311 The system control section 30h causes the pattern generating section 31 of the error measuring section 30e to start to generate data having a predetermined pattern 25 The data generated by the pattern generating section 31 is transmitted to the network terminal unit via the cross-connect section 30b, the subscriber circuit 30c - 19 and the switch 30d, is reflected back from the network terminal unit, and is received by the error detecting secti on 32 through the same route.

ES321 The error detecting section 32 determines whether or not generation of the data has been completed.

If the data generation is completed, the flow proceeds to Step S33; if not, execut:Lon of Step S32 is repeated.

[S33] The error detecting section 32 compares the received data with the original data generated by the pattern generating section 31, to thereby compute an error occurrence rate.

[S34] The error detecting section 32 notifies the system control section 30h of the error occurrence rate computed In Step S33.

15. [S351 The system control section 30h controls the subscriber circuit 30c and causes the same to transmit data In which the predetermined control bit (control bit requesting loopback) is set OFF, to the network terminal unit.

As a result, the detecting section 21, shown in FIG. 3, of the corresponding network terminal unit detects the OFF state of the control bit and notifies the loopback section 22 of the detected state. In accordance with the notification from the detecting section 21, the loopback section 22 stops the loopback of data.

According to the process described above, a predetermined network terminal unit can be made to perform - 20 loopback of data so that the error occurrence rate can be measured.

Referring now to FIG. 10, the process "LOOPBACK TEST OF SUBSCRIBER CIRCUITw shown in Step S9 of FIG. 5 will be described in detail. Upon start of the process shown in the flowchart, the following steps are executed.

[S40] The system control section 30h controls the subscriber circuit 30c and sets the same so as to reflect data from the cross-connect section 30b back to the same section.

[S41] The system control sectlon 30h causes the pattern generating section 31 of the error measuring section 30e to start to generate data having a predetermined pattern The data generated by the pattern generating section 31 is supplied to the subscriber circuit 30c via the cross-connect section 30b. The subscriber circuit 30c reflects the data supplied thereto back to the cross-connect section 30b. As a result, the reflected data Is received by the error detecting section 32. 20 [S421 The error detecting section 32 determines whether or not generation of the data has been completed. If the data generation is completed, the flow proceeds to Step S43; if not, execution of Step S42 Is repeated. [S431 The error detecting section 32 compares the received data with the original data generated by the pattern generating section 31, to thereby compute an error occurrence rate.

JS44] The error detecting section 32 notifies the system control section 30h of the error occurrence rate computed in Step S43.

[S45] The system control section 30h supplies a 5 control signal to the subscriber circuit 30c to stop the loopback operation.

According to -the process described above, the subscriber circuit 30c can be made to perform loopback of data so that the error. occurrence rate can be measured.

As described above, a subscriber transmission device embodying the present invention makes it possible to lessen the burden on the operator who conducts tests and also to carry out the subscriber test in a short time and at low cost.

In the foregoing description

ISDN is taken as an example of communication network and V5.2 Is referred to as an example of communication protocol. It should, however, be noted that the present Invention is not limited to such configuration alone.

As described above, according to an embodiment of the present invention, a subscriber transmission device arranged between an exchange and network terminal units for relaying Information therebetween according to a predetermined protocol comprises target specifying means for specifying a predetermined network terminal unit which is a target of test, ongoing communication detecting means for detecting presence/absence of ongoing -communication of the predetermined network termi nal unit specified by the target - 22 specifying means, and testing means for testing a characteristic related to a state of communication with the network terminal unit specified by the target specifying means, in accordance with a result of the detection by the ongoing communication detecting means, whereby a subscriber test can be conducted in a short time with reliability.

The foregoing.-Is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to 10 those skilled in the art, it, Is not desired to limit the Inventlon to the exact construction and applicatIons shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the Invention in the appended claims and their 15 equivalents.

Claims

CLAIMS:

A subscriber transmission device arranged between an exchange and network terminal units f or relaying inf ormatlon therebetween according to a predetermined protocol, comprising:

target specifying means for specifying a predeterm:Lned network terminal unit which is a target of test; ongolng communication detecting means for detecting presence/absence of ongoing communication of the predetermIned network terminal unit specified by said target specifying means; and testing means for testing a characteristic related to a state of communication with the network terminal unit specJ-f led by said target specifying means, in accordance with a result of the detection by said ongoing communication detecting means.
2. The subscriber transmission device according to claim 1, wherein said testing means includes electrical characteristic measuring means for measuring an electrical characteristic of a communication line connected to the network terminal unit.
3. Thesubscriber transmission device according toclzimlar- 2, wherein said testing means includes pattern data generating means for generating data having a predetermined - 24 pattern, first loopback means for causing the data generated by the pattern data generating means to be reflected back from a subscriber circuit provided Internally in said subscriber transmission device, second loopback means for causing the data generated by the pattern data generating means to be reflected back from the network terminal unit, and. error detecting means for detecting error Included in the data reflected back by the first or second loopback means.
4. The subscriber transmission device according to claim 3, further comprising fault location estimating means for comparing error Included in the data reflected back by the first loopback means with error included In the data reflected back by the second loopback means, to estimate a location where fault has occurred.

I.

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5. A method of testing a state of communication between a subscriber transmission device, arranged between an exchange and network terminal units for relaying information therebetween according to a predetermined protocol, and a network terminal unit, comprising:

specifying which one of the network terminal units is a target of the test; detecting the presence or absence of ongoing communication by the specified network transmission unit; and testing a characteristic relating to a state of communication between the subscriber transmission device and the specified network terminal unit in dependence on the result of the detecting step.
6. A subscriber transmission device substantially as described herein with reference to and as illustrated in the accompanying drawings.
7. A method of testing substantially as described herein with reference to and as illustrated in the accompanying drawings.