AU2433999A - A cabling testing device - Google Patents

Description

WO 99/39493 PCT/GB99/00351 A CABLING TESTING DEVICE BACKGROUND TO THE INVENTION THIS invention relates to a cabling testing device, and in particular to a cabling testing device for testing connections in telecommunications cabling. Telecommunications distribution networks generally have a branched configuration from main distribution frame equipment located at exchanges through to individual lines via a series of distribution boxes. Each of the distribution boxes are fitted with distribution frames carrying connection and disconnection modules for distributing between 10 and 4800 or more wire pairs or lines. Once the various wire pairs or lines have been connected, they need to be tested. This is typically done by using a two-prong tester to sequentially short out corresponding terminals and then generating a tone in that line which is connected via the terminals. The post-installation and fault testing procedure which is followed using such a tester is particularly long and arduous, in particular where 1000 or more individual pair connections require testing. In addition to being time consuming, there is also a possibility of terminals being inadvertently skipped out in the testing procedure. oT-im or'i'TriryTTrIP'T7 Tll 17 rir /"1r'%..1_ 14[' WO 99/39493 PCT/GB99/00351 -2 SUMMARY OF THE INVENTION According to the invention there is provided a connection testing device for testing connections in telecommunications cabling, the testing device comprising at least one multi-terminal pair plug-in module for insertion into one of a plurality of corresponding multi-terminal pair connection or disconnection blocks, serial switching means for sequentially switching through individual terminal pairs in the block, each terminal pair being arranged to receive first ("A") and second ("B") wiring legs, parallel switching means for selectively connecting or disconnecting in parallel all of the terminal pairs in the block for simultaneously testing all of the connections in the block and indicator means for indicating when a valid or invalid connection has been established in respect both of a particular block and of the terminal pairs in the block. Typically, the receipt or non-receipt of a signal is indicative, respectively, of a valid or invalid connection. Preferably, the serial switching means comprises a first serial switch component for sequentially switching through the "A" legs of each terminal pair, and a second serial switch component for sequentially and simultaneously switching through the "B" legs of each terminal pair, the first and second serial switch components being mechanically interlinked. Conveniently, the parallel switching means comprises at least a first parallel switch component for simultaneously connecting all of the "A" legs in a terminal pair to a first common output terminal and the second parallel switch O Tmc'T[Tr'ITrITW CLTT"I rF

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"..1, OIA WO 99/39493 PCT/GB99/00351 -3 component for simultaneously connecting all of the "B" legs in a particular terminal pair to a second common output terminal. Advantageously, the testing device includes a polarity indicator circuit for indicating the polarity of current flow, a short circuit sub-circuit for selectively providing a short circuit across single or parallel terminal points and an earth terminal for selective connection to the A- or B-legs. Preferably, the device includes switching means for selectively switching between signal transmit and receive mode, in which the signal generator and the indicator means is active, and signal receive mode, in which only the indicator means is active. The cabling testing device of the invention is typically used to carry out a number of different tests, including single tone receive and transmit tests multi-pair parallel tone receive and transmit tests, polarity monitor tests, earthing tests and short circuiting tests, both of the latter being in respect of single and multiple connections, in respect of both live and dead wiring. Conveniently, the plug-in module forms part of at least one separate plug-in adaptor lead assembly which is connectable via a common plug-in connector to a control housing carrying the parallel and serial switching means and the indicator means. A plurality of different plug-in adaptor lead assemblies may be provided, each carrying a differently configured plug-in module depending on the type of connection or disconnection block being tested. Q(TTrl~IDqTTT L' C!TXE'E'T MD .. 1 V/\ WO 99/39493 PCT/GB99/00351 -4 Typically, each of the multi-terminal plug-in modules include multi-prong Quante® and Krone® modules. These may include voltage arrestor magazine housings or "lightning blocks" which have been appropriately modified. The testing device may further include a high voltage testing sub-circuit comprising a high voltage triggering device and indicator means responsive to the triggering device. By the term "high voltage" is typically meant DC voltages in excess of 200V, which are typically of the level encountered in pair gain systems. The high voltage testing sub-circuit may include a high voltage triggering device such as a thyristor, and indicator means such as an LED responsive to the triggering device. Advantageously, the first and second switch components are combined in a one pole two-way for twelve-way switch assembly. The first and second parallel switch components may advantageously be combined in a four pole six wafer three-way switch assembly. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a schematic. view of a typical prior art telecommunications distribution network; Figure 2 shows a simplified circuit diagram of a first embodiment of a Q TT,"OrVIrr"TTrVV~ QY: GrliD ., 14 WO 99/39493 PCT/GB99/00351 -5 connection testing apparatus of the invention used for testing connections in the network of Figure 1; Figure 2A shows a detail of a parallel switch forming part of the circuit of Figure 2; Figure 3 shows a pictorial view of the first embodiment of the connection testing apparatus of the invention; Figure 4 shows a circuit diagram of a second embodiment of a connection testing apparatus of the invention; Figure 5 shows a pictorial view of a connection testing apparatus housing the circuitry of Figure 4; Figure 6 shows a pictorial view of a plug-in adaptor for use in conjunction with the connection testing apparatus of Figure 5; Figure 7 shows a circuit diagram of a third preferred embodiment of a connection testing apparatus of the invention; and Figure 8 shows a pictorial view of the connection testing apparatus housing the circuitry of Figure 7. DESCRIPTION OF EMBODIMENTS Referring first to Figure 1, part of a typical telecommunications distribution IT T'in OrI' T Tr1Ir'II = ' V,'l"g

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rV .I,, O)AC WO 99/39493 PCT/GB99/00351 -6 network comprises a central exchange 1 having a switching side 1A and a cable connection side in the form of a main distribution frame IB carrying distribution strips 2A to 2N for the connection of wire pairs of cables. Each strip is typically configured to accommodate modules for connecting up to 2400 telephone wire pairs or lines, with each line being associated with a particular telephone number. Up to 200 or more individual strips can be provided, with the result that an exchange can have a capacity of 160 000 lines or more. From the central exchange, individual distribution cables 3 containing 2 400 pairs or more of wires are fed to individual street distribution cabinets (SDC's) 4 via branch cables 3A, 3B and 3C, which typically accommodate from 200 to 1000 lines. Each SDC 4 comprises an array of "upstream" connection frames 4A and an array of "downstream" connection frames 4B, each of which are arranged to accommodate around 1000 lines. The "upstream" frames 4A are linked directly to the incoming cabling from the exchange, and the "downstream" frames 4B are linked in this case via 300 pair cabling 5A, and 40 and 50 pair branch cabling 5B to the "upstream" frames 6A of a distribution point (DP) station 6, which is similarly provided with a series of "downstream" frames 6B. Each of the frames is designed to accommodate up to 400 lines or wire pairs. Cabling 7A, 7B and 7C in turn leads to local stations 8 comprising "upstream" and "downstream" frames 8A and 8B which typically form part of a switchboard. Individual telephones 9A, 9B and 9C are connected via respective lines 9D, 9E and 9F to the "downstream" panel 8B of the switchboard. QcTT oTor'T'TTrTE cq"E[l ri

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" .. !, '14% WO 99/39493 PCT/GB99/00351 -7 It should be appreciated that the telecommunications distribution network in Figure 1 represents a simplified version of a network. In most cases, many more intermediate connection stations or distribution boxes are provided. Colour coding is customarily used to track individual wires. However, the range of colours and colour combinations is limited, and such colour coding is generally not adhered to, especially when wires are periodically replaced, leading to considerable problems in tracking which are only partly alleviated by the prior art twin prong tester mentioned above. Referring now to Figure 2, a first basic embodiment of a cabling testing device 10 of the invention comprises a multi-contact connection plug which may be in the form of a Quante@, Krone@ or similar voltage arrester magazine housing or lightning block 12 which has been modified by the removal of the over-voltage arresters so that an open circuit condition exists between first "A" terminals 1.1 to 1.10 and second "B" terminals 2.1 to 2.10 respectively. An earth bus 14 extends behind the terminals, and is provided with earth plugs 14.1 and 14.2. The bus 14 is connected to an earth input and output plug terminal socket 16 for selectively earthing the terminals 1.1 to 1.10 or 2.1 to 2.10 of the plug 12. The "A" and "B" legs from the plug 12 are fed via a connection strip 18 to respective two-way twelve position series rotary switches 20 and 22. The rotary switches 20 and 22 are each provided with twelve contact terminals 24 and a rotary wiper blade 26 for selectively switching between the contact terminals. Each of the rotary series switches 20 and 22 also has respective common terminals 28 and 30 which are wired to "A" and "B" leg plug terminal sockets 32 and 34 respectively. OYTTTnb rV rIrTTrlr1M'I =, 1 l'rlr M"E~..i, "WAC' WO 99/39493 PCT/GB99/00351 -8 The circuit is also provided with four six-way three position parallel rotary switches, namely rotary switches 36.1 and 36.2 which together share the "B" leg wiring fed in parallel from the connection strip 18, and parallel rotary switches 38.1 and 38.2 which share the parallel "A" leg wiring from the connection strip 18. For the sake of clarity, only the wiring from "A" legs 1.1, 1.2 and 1.10 has been indicated, together with the wiring from "B" legs 2.1, 2.2 and 2.10. The structure of the six-way three position switches is illustrated in more detail in Figure 2A, from which it is clear that each six-way three position switch is provided with six sets of three output terminal arrays 40.1 to 40.6 and a common line 41. In the pc-mounted version, six wiper contacts 42 are connected in a spider configuration to a central hub 44 of a wafer 45. The three output terminals include a central common terminal 41.1 which is wired to the common line 41. Outer active input terminals 45.1 to 45.6 are connected respectively to the B terminals 2.1 to 2.6. The other outer terminal 46 is open circuited. The switch is rotatable on the hub 44 between a disconnected open circuit position indicated in broken outline at 47 and a connected position indicated in solid outline, in which all of the incoming lines are simultaneously connected in parallel via the active terminals 45.1 to 45.6 to the common line 41. In an alternative mechanical version, the wafer 45 has four equi-spaced terminals on one side and two on the other. The common terminals 41B of the "B" leg switches 36.1 and 36.2 are linked to terminal 11 of the "B" leg serial switch 22, and the common terminals 41A of the "A" leg parallel switches 38.1 and 38.2 are connected to terminal 11 of the "A" leg serial switch 20. Both the A leg switch 38.2 and the B leg switch T'TM~qI rTqrVIPIi QTTIVTI' l

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f".. 14' WO 99/39493 PCT/GB99/00351 -9 36.2 is provided with four working terminals for respective connection to the remaining four B terminals 2.7 to 2.10 and A terminals 1.7 to 1.10. A tone generator circuit 50 is shunted across the "A" and "B" legs 32.1 and 34.1 leading to the "A" and "B" output terminal sockets 32 and 34. The tone generator circuit 50 comprises a buzzer 52, a tone generator 54, a 9-12V DC battery 56, a resettable fuse 58 incorporated in the tone generator and an on/off switch 59. A three-way switch 60 is coupled to the tone generator, and is used to vary the tone output either by altering the pitch or the tone interval. A three-way selector switch 61 has a common terminal 61.1 connected to the B leg, a battery terminal 61.2 for connection to the battery 56 and the tone generator 54 and a buzzer terminal 61.3 for connection to the buzzer 52. A short circuit switch 62 spans the "A" and "B" legs 32.1 and 34.1, and a polarity sensing sub-circuit 64 is similarly shunted in parallel across the "A" and "B" legs, and comprises a resettable fuse 66, a switch 68, a bi-directional diode 70 and a resistor 72. Referring now to Figure 3, a pictorial view of the testing device 10 is shown comprising a housing 76 from which respective Quante@ and Krone@ connection plugs 12A and 12B extend. This allows the testing device to be used to test either Quante® or Krone@ connection or disconnection modules, which makes it a lot more versatile, in particular in the not uncommon situation where a combination of such modules is found at a particular distribution box installation. The box or housing 76 also carries a twelve position serial switch 78 which incorporates both the two-way twelve position series rotary switches 20 and 22 as wafers on a single switch hub or axle. The six-way three position parallel switches 36.1, 36.2 and 38.1 and 38.2 are also combined into a single parallel rotary switch 80 which has a common axle or iTn Tr"I TTrl"VIV OWy rr'rl

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nnI -jI i c WO 99/39493 PCT/GB99/00351 -10 hub for enabling simultaneous rotation of the separate switch wipers 42. The additional three- and two-way switches referred to with reference to Figure 2 are also positioned on the housing 76 in the manner illustrated, together with the A and B terminal sockets 32 and 34 and the earth socket 16. The testing circuit 10 is able to operate a number of different testing modes. These can be summarized as follows. Single Tone Receive Test This testing mode is used to test for an input tone on the "A" or "B" legs. The three-way switch 61 is moved to receive terminal 61.3, in which it is connected to the buzzer 52. The wiper 26 is moved to terminal 1 on each of the serial switches 20 and 22 for connection to the respective A and B legs and the Krone@ or Quante@ connection plug 12A or 12B is inserted into the corresponding Krone@ or Quante® module being tested. The "A" and "B" terminal sockets 32 and 34 may be used if the connections to the individual telephones 9A, 9B and 9C are being tested. The serial switch 78 is then sequentially switched through from terminals 1 to 10 until a tone is heard, which is indicative of the particular set of terminals linking a particular telephone line to a switchboard in response to a remote switchboard-based tone generator. Single Tone Transmit Test In this mode, the same sequence of operations is carried out, save that the SUBSTITUTE SHEET (RULE 26) WO 99/39493 PCT/GB99/00351 -11 three-way switch 61 is moved from receive terminal 61.3 to the transmit terminal 61.2, and the tone from the tone generator 54 is transmitted sequentially along the "A" and "B" legs as the wiper arms 26 of the serial switches 20 and 22 are simultaneously rotated. In both of the single tone receive and transmit modes, the wipers 42 on the parallel switches 36.1 to 38.2 are turned to their "off' position indicated at 46. Ten Pair Tone Receive and Transmit Tests In both of these test modes, the wipers 42 are turned to their Figure 2A "on" position in which all of the lines of the "A" and the "B" legs are simultaneously connected in parallel with the common terminals 41A and 41B. At the same time, the wipers 26 are moved to their terminal 11 position. In the tone receive mode, the tone generator circuit 54 is disconnected, by moving the three way switch 61 to terminal 61.3 for connection to the buzzer 52, whereas in the transmit mode, the switch 61 is moved to connect with terminal 61.2. The ten pair receive mode is used initially simultaneously to identify if any one of the terminals in a particular terminal connection block are receiving tones. In the event of the buzzer sounding, this is indication that one of the terminal pans is receiving a tone. Thereafter, the single tone receive mode is reverted to isolate the particular terminal pair which is receiving the tone. The ten pair transmit mode is used for the simultaneous transmission of ten tones along the "A" or "B" legs. Q'YTTDrlTTrTTr12U CIJII'l~rI M-ID 141 WO 99/39493 PCT/GB99/00351 -12 Polarity Monitor Test This mode of operation is used for DDI/DDO (direct dial in/direct dial out) lines, which are polarity sensitive. The wipers 26 are moved back to terminal 1 on the respective serial switches 20 and 22, the wipers 42 are disconnected or earthed and the switch 68 is closed. The polarity of the signal from the "A" and "B" legs is then sequentially checked by rotating the wipers 26 sequentially through terminals 1 to 10. If the two-way diode 70 glows green, this is indicative of the "A" leg being the battery or powered leg, and if the two-way diode 70 glows red, then this is indicative that the "B" leg is the battery or powered leg. The polarity monitor test is conducted once the signal has been located using the ten pair receive and transmit modes followed by the single tone receive and transmit modes of testing. Earth-A and -B Leg Single and Ten Way Tests In the earth "A" leg testing mode, the "A" leg output socket 32 is shorted to the earth socket 16. In the earth "B" leg test, the "B" leg terminal socket 34 is shorted to the earth socket 16. In the ten way version of these tests, the wipers 26 on the serial switches 20 and 22 are switched to the common terminal 11, and the wipers 42 on the parallel switches 36.1 and 36.2 and 38.1 and 38.2 are sequentially activated. Short Circuit - Single and Ten Way Tests In this test, the short circuit switch 62 is closed and the serial and parallel 1T DQTTTTFTr1r'V 0"l["iT rl

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PD,. 0 )1 1 WO 99/39493 PCT/GB99/00351 -13-. switches of the "A" and "B" legs are.sequentially operated in the manner previously described. Referring now to Figure 4, a second embodiment of a cabling testing device 32 of the invention is provided with a twenty five pin D-type female computer plug 84. Those components of the second embodiment which are similar to the corresponding components of the first embodiment have, for ease of reference, been identified with the same numerals, and where the description of the operation of the circuit is substantially identical to that of the first embodiment, the reader is referred to the relevant prior portion of the description. For ease of reference, the output pins of this plug are numbered from lA to 10A in respect of the A-leg pins, and from IB to 10B in respect of the B-leg pins. As is clear from Figure 5, the D-type plug 84 essentially replaces the Krone® plug 10 OA and the Quante® plug 10B illustrated in Figure 3 of the first embodiment. Rather than being integral with the housing, the second embodiment includes a set of plug-in adaptors, two of which are shown at 85A and 85B. Referring also to Figure 6, the first adaptor 85A includes a complemental male D-type computer plug 86A from which a wiring harness 88A having at least twenty leads extends. The wiring harness 88A terminates in the Quante® connection plug 10 OA which was previously mounted directly onto the housing 76 of the testing device. Similarly, the adaptor 85B comprises a complemental D-type male computer plug 86B from which a harness 88B extends and terminates in the Krone® connection plug 10B. Naturally, depending on the connection or disconnection modules to be tested, various other adaptors can be provided with appropriately modified connection plugs. OjrTD TQr~TrVViITT'3 OYTIM 1 "ID '.IJ WO 99/39493 PCT/GB99/00351 -14 In addition, the wiring harnesses 88A and 88B are sufficiently long to allow banks of disconnection and connection modules to be tested without having to move the housing 90. The numbered terminals 1A to 10A and 1B to 10B at the computer plug 84 lead to corresponding terminals 1A to O10A and IB to O10B on a one pole twelve-way switch 92 comprising switch wafers 92A and 92B for the respective A and B legs. The switch 92 effectively replaces the two series rotary switches 20 and 22 of Figure 4. The terminals lA to 10OA and 1B to 10OB at the computer plug 84 also lead to a four pole three-way six wafer switch assembly 96 which effectively replaces the parallel rotary switches 36.1, 36.2, 38.1 and 38.2 of Figure 5. The switch assembly comprises six individual wafers including three A-leg wafer terminals 96A1, 96A2 and 96A3 and three B-leg wafer terminals 96B 1, 96B2 and 96B3. Various other components of the circuit are substantially identical to those illustrated in Figure 5. In Figure 7, a third embodiment of the cabling testing device is shown incorporating a number of modifications and improvements. Those components of the third embodiment which are similar or identical to the corresponding components of the second embodiment have been identified with the identical numerals, and where the description of the operation of the circuit is the same as that of the first and second embodiments, the reader is referred to the relevant prior portions of the description. A protective capacitor Cl is connected between the buzzer 52 and the terminal socket 32 to protect the buzzer against voltages in excess of 100V. A high TTUl TTTTTTI' QT--PIV 1rT tf1luD 1' WO 99/39493 PCT/GB99/00351 -15 voltage detection sub-circuit 100 is connected between the protective capacitor C 1 and a high voltage terminal 101.1 of a three-way switch 101. The three-way switch includes a polarity sensing terminal 101.2 which forms part of a polarity sensing sub-circuit 64A. As a result, the rocker of the switch 101 can be moved between a polarity sensing mode and a high voltage sensing mode. A high voltage sub-circuit comprises a thyristor 102 arranged to trigger at a voltage input in excess of 200 volts DC, a bicolour LED 104 which lights up in the event of the thyristor 102 triggering, and a voltage lowering resistor 106. The bicolour LED 104 changes colour (e.g. from red to green) depending on the direction of current through the LED 104. In other words, the LED allows the high voltage sub-circuit also to have a polarity sensing function in which it detects whether an A leg or a B leg is being received at the A and B leg input terminals 32 and 34. The high voltage detecting sub-circuit 100 allows the testing of voltages higher than 200 volts DC. The need to test such relatively high voltages occurs when pair gain systems are being tested, particularly to warn the testing technician that high DC voltage exists on, say, one of the cables in the pair. In Figure 8, a complete cabling testing device 110 is shown which has a layout similar to that illustrated in the second Figure 5 embodiment. A D-type female computer plug 84 is located on the rear face of the housing, and the one pole two wafer twelve-way switch 92 and a four pole three-way six wafer switch assembly 96A is located adjacent the twelve-way switch 92. The upper face of the housing is formed with the A, B and ground terminals 32, 34 and 16, together with the bicolour polarity and high voltage indicating LED's 70A QTTnQTTT1rr T1 '1YUT ( M.A. ')A' WO 99/39493 PCT/GB99/00351 -16 and 104. A series of five rocker switches are also mounted on the front face of the housing, including the three-way polarity/high voltage switch 101, and a three-way tone output control switch 60. A short circuit switch 62 spans the A and B legs, and a tone transmit and tone receive switch 61 is provided for allowing the tester to be selectively operated in the tone receive and tone transmit modes. Finally, a battery on-off switch 59 is provided. The testing procedure is commenced by switching the rotary switch 92 to the correct position (i.e. from 1 to 10) depending on which of the particular A and B legs being tested. The rocker switch 101 is then turned to the high voltage sensing position in which it contacts terminal 101.1, with the selector switch 96A being in the off position. If the LED 104 lights up, then this is indicative that the pair being tested carries a high voltage in excess of 200V DC. The polarity of the voltage can also be tested depending on the colour of the high voltage indicating LED 104. The cabling testing device of the invention is used for both live and dead wiring for testing both the transmission and receipt of signals. The ability of the testing device to operate effectively in testing live wiring is particularly advantageous, in that it reduces down time and labour and speeds up the testing procedure. This single device replaces a host of prior art equipment, including a tone generator and associated probes, various types of test prongs as well as a telephone hand patrol. A separate shorting screwdriver and/or short circuit key equipment also becomes redundant. In addition, the testing device of the invention is able to locate split legs on the same connection or disconnection block in cases where the colour coded wiring does not follow the correct order, with, for example, the white B leg 1TD'T'IrlTrlTTITr2 .' QT rT .

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.1" 'IKi WO 99/39493 PCT/GB99/00351 -17 wire being connected between terminal lB of a distribution point block to terminal 2B of a local block, and vice versa. The prior art equipment required that testing from the exchange needed close co-operation with a test clerk at the exchange. With the testing device of the invention, testing of lines from the exchange downwards can be accomplished merely by sending a constant voltage from the exchange on the particular line being tested, after which the short circuit, ten pair transmit and single tone transmit tests can be conducted for testing connectivity. Krone®, Quante@ and other types of manufacturers' blocks, which often appear in a mixed format on the same distribution frame, may also be tested using the testing device of the invention, as well as RVJ or telephone jack connections. The testing device is also suited to conducting so-called "Mega" tests, in which the location of a fault along the line is measured by transmitting the current sequentially through the A and B legs of the line and measuring the line resistance. SUBSTITUTE SHEET (RULE 26)

Claims (14)

1. A connection testing device for testing connections in telecommunications cabling, the testing device comprising at least one multi-terminal pair plug-in module for insertion into one of a plurality of corresponding multi-terminal pair connection or disconnection blocks, serial switching means for sequentially switching through individual terminal pairs in the block, each terminal pair being arranged to receive first ("A") and second ("B") wiring legs, parallel switching means for selectively connecting or disconnecting in parallel all of the terminal pairs in the block and indicator means for indicating when a valid or invalid connection has been established in respect both of a particular block and of the terminal pairs in the block.

2. A connection testing device according to claim 1 in which the serial switching means comprises a first serial switch component for sequentially switching through the "A" legs of each terminal pair, and a second serial switch component for sequentially and simultaneously switching through the "B" legs of each terminal pair, the first and second serial switch components being mechanically interlinked.

3. A connection testing device according to either one of the preceding claims in which the parallel switching means comprises at least a first parallel switch component for simultaneously connecting all of the "A" legs in a terminal pair to a first common output terminal, and a second parallel switch component for simultaneously connecting all of the corresponding "B" legs in the particular terminal pair to second QTTUTTTTTT T-T11T rDula 91 WO 99/39493 PCT/GB99/00351 -19 common output terminal, the first and second parallel switch components being mechanically interlinked.

4. A connection testing device according to any one of the preceding claims which includes a polarity indicator circuit for indicating the direction of current flow through the terminal pairs in the block.

5. A connection testing device according to any one of the preceding claims which includes a short circuit switch for selectively providing a short circuit across single or parallel terminal points and an earth terminal for selective connection to the A- or B-legs.

6. A connection testing device according to any one of the preceding claims which includes an active signal generator for transmitting locating or testing signals either in parallel via the parallel switching means or serially via the serial switching means.

7. A connection testing device according to claim 6 which includes switching means for selectively switching between signal transmit and receive mode, in which the signal generator and the indicator means is active, and signal receive mode, in which only the indicator means is active.

8. A connection testing device according to any one of the preceding claims which is arranged to carry out a number of different tests, including single tone receive and transmit tests, multi-pair parallel tone receive and transmit tests, polarity monitoring tests, earth leakage tests and short circuit tests, both of the latter being in respect of single WO 99/39493 PCT/GB99/00351 -20 and multiple connections, for both live and dead wiring.

9. A connection testing device according to any one of the preceding claims in which the plug-in module forms part of at least one separate plug-in adaptor lead assembly which is connectable via a common plug-in connector to a control housing carrying the parallel and serial switching means and the indicator means.

10. A connection testing device according to claim 9 in which a plurality of different plug-in adaptor lead assemblies are provided, each carrying a differently configured plug-in module depending on the type of connection or disconnection block being tested.

11. A connection testing device according to any one of the preceding claims which includes a high voltage testing sub-circuit.

12. A connection testing device according to claim 11 in which the high voltage testing sub-circuit includes a high voltage triggering device and indicator means responsive to the triggering device.

13. A connection testing device according to claim 2 in which the first and second serial switch components are combined in a one pole two wafer twelve-way switch assembly.

14. A connection testing device according to claim 3 in which the first and second parallel switch components are combined in a four pole six wafer three-way switch assembly. QlTTIrQTTTTTT" CITl' T I' l, hM i