GB2212006A - Capacitive plug for line verification testing - Google Patents

Abstract

A plug (23) for use in line verification testing for pre-cut-over of telecommunications switching apparatus is in the form of a plastics body (24) and two elongate members (25) having opposed conductive layers (26, 31), separated by an insulative layer (27). A chip capacitor (28) is mounted on each elongate member (25), and a.c. couples the outer conductive layers (26 and 31) on which it is mounted. Cylindrical guides (29) extend from the body to assist location when inserted in the test-jack. An aperture (30) allows a member of plugs to be threaded together and rapidly removed together when cut-over is required. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO LINE VERIFICATION TESTING This invention relates to line verification for pre-cut-over testing of telecommunications switching apparatus and to a plug for such use.

Such configurations are known for example in GB Patent Publication GB 2164504. This discloses a wedge shaped plug in the form of a printed circuit board (pcb) with conductive lands on a portion of the board with two disc capacitors soldered on one face of the board. Typically the size of the wedge would be 25 x 20 mm. Such a configuration is suitable for some exchanges but not the more modern exchange blocks.

The present invention is concerned with providing a configuration suitable for these systems.

According to the invention there is provided a plug for use in line verification for pre-cut-over testing of telecommunications switching apparatus, said plug comprising: a body of electrically insulating material; two elongate connector means extending from said body, said connector means each comprising two opposed conductive layers separated by a layer of electrically insulating material and capacitive means provided thereon to a.c. couple the conductive layers.

The plug preferably includes means for retaining a withdrawal cord or the like.

The invention will now be described by way of example only with reference to the drawings in which: Figure 1 shows the general arrangement of equipment for performing line verification; Figure 2 shows one embodiment of a plug made in accordance with the present invention; Figure 3 shows the plug of Figure 2 viewed from below: Figure 4 shows one of the elongate members forming part of the plug of Figure 2 and 3; Figure 5 shows a side view of the plug; Figure 6 shows a cross-sectional view of the plug taken along the line A-A of Figure 2; Figure 7 shows an exploded view of a two-part body used to construct a further embodiment of the plug.

Figure 8 shows the second embodiment as assembled; and Figure 9 is a cross-section view of the plug taken along the line B-B of Figure 8.

Referring to Figure 1, an existing (old) telecommunications switching apparatus 10 in the form of a telephone exchange is connected, as is known in the art, to test jacks 11 on the exchange side of a main distribution frame (MDF) 12 by respective pairs of leads 13. Each test jack 11 is connected by an old jumper 14 to a corresponding pair of terminals 15 on the line side of the MDF 12, which in turn are connected to the A and B lines to a customer.

A replacement switching apparatus (new exchange) 16 is similarly connected to associated test jacks 17 on the MDF 12 which are connected by respective new jumpers 18 to their associated pairs of terminals 15.

A line verification tester (LVT) 20 is connected, again as known in the art, to respective test access points of the old and new exchanges 10, 16, and comprises a computer based control unit 21 and an interface unit 22. The control unit 21 has access to all the necessary data on directory numbers and exchange numbers to enable parallel paths to be set up through both exchanges to a given directory number, i.e. a particular pair of terminals 15.

A plug 23 is inserted into a test jack 17. Within the plug 23 are capacitors which allow a.c. coupling of the faces of the respective contacts in the plug as described in more detail below, when inserted into the test jack 17.

The LVT 20 supplies respective selection signals to the exchanges to establish parallel paths to a selected pair of terminals 15, then applies one or more AC test signals to each of the A and B wires of the test access of one of the exchanges, measures the signals received on the corresponding wires at the test access of the other exchange and performs a pre-set analysis to determine whether the tested path through the new exchange is correct and acceptable.

After the new exchange 16 and the new jumpering 18 has been completely checked it can be brought into service by removing all the plugs 23, and the old exchange 10 can then be removed from service.

Refering now to Figures 2, 3, 5 and 6 there is shown a plug 23, which includes a body 24 made of insulative material (e.g. plastics material). Two elongate members 25 are provided located on the body 24 and extending therefrom. The elongate members 25 each include two opposed outer conductive layers 26, 31 on the major faces and insulative layer 27 (see Figure 4).

Mounted on each of the elongate members 25 is a chip capacitor 28 (e.g. 1000 pF). Each chip capacitor 28, a.c.

couples the conductive layers 26 and 31 of the elongate member 25 whilst preventing the passage of d.c. there between. The elogate member insulative layer 27 is typically a glass fibre material with conductive layers 26, 31 of copper. The layer 26 extends substantially over the entire face of the insulative layer 27 but the layer 31 has a break in this layer in the region of the chip capacitor 28. The capacitor soldered on either side of this break effectively a.c. couples both parts of this layer 31, and the hole 32 through the member 25 is plated with copper or other conductive material (through the-hole-plating) to provide a conductive path between the region of layer 31 adjacent the hole and the underlying layer 26. This technique allows a flush surface on conductive layer 26 to be provided. No protruding wires are necessary for a.c.

interconnection of conductors 26 and 31. A rectangular aperture 34 extending through layers 26, 27 and 31 cooperates with a locating lug 36 on the body 24 to positively hold the members 25 when assembled on the body 24 of the plug 23. A channel defined by edges 35 can be provided in the body to aid this location. The body includes four extensions 38 which give support to the elongate members 25 whilst allowing some flexing of these members towards the centre of the plug during insertion into the test jack. In addition, two cylindrical portions 29 extend from the body to act as guide members. When the elongate members 25 are inserted into a test jack 17, the ends of the centrally disposed cylindrical members 29 fit into respective holes in the test jack 17, thereby ensuring that the elongate members 25 are correctly located within the test jack.This is so that when the plug 23 is inserted into a test jack 17, the conductive layers 26 and 31 of one elongate member are in contact with respective contacts of one of the contact pairs (say for the A wire), and the conductive layers 26 and 31 of the second elongate member are similarly in contact with respective contacts of the other contact pair (B wire). An aperture 30 is formed from the body 24, and enables a wire or cord to be threaded through a large group of plugs 23. The aperture is positioned substantially perpendicular to the pane of the major surface of the elongate members 25 to allow the cord to hang vertically through the plugs when they are used horizontally. On cut-over to the new exchange, plugs of a group can be pulled out of the test jacks substantially simultaneously. Thus cut-over of even a large exchange can be achieved in a few minutes or less by a few commissioning engineers rapidly extracting the groups (preferably more than one group at a time) typically well in excess of 1000 line pairs.

The configuration employed allows a small sized plug to be fabricated to ensure successful operation on closely packed test jacks. Typically the distance between the outer edges of the two cylindical portions 29 (see Figure 3) will be only 9 mm and the distance between the outer edges of opposing elongate members 25 will be only 8 mm.

The channeled extensions 38 not only supports the members 25 but give some damage protection to the surface mounted chip capacitors 28 as these are situated between pairs of the extensions 38. These capacitors could alternatively be mounted higher on the members 25 towards the plated hole 32 (with associated modification to the position of the break in the conductive layer 31) and the members 25 could then be inverted so that the chip capacitors could be located within the voids 37 in the body (see Figure 6) to provide even better protection. Rather than relying on the lug 35 for fixing, alternatively an insulated pin could be provided to pass through the body and aperture 34 and could be heat deformable to provided headed portions at each end for positively securing the members 25 to the body 24.

In an alternative embodiment shown in Figures 7 to 9, a two part body 40, 41 is provided which interlocks on assembly. Each part is configured to receive a portion of both members 25 so that these parts join adjacent the outer major face of these members.

The parts 40 and 41 have a generally planar walled portion which terminates in extensions 38 and cylindrical portion 29. A pair of resilient perpendicular members 41 extend from the wall of part 40 and terminate in lugs 42 which locate in a slot-like aperture 50 on part 41. A perpendicular extension 51 ends in a finger portion 54 for locating in aperture 43 in part 40. The box-like portion 55 of body 41 is configured to accomodate part of the members 25.

The chip capacitors 28 mounted thereon are accomodated in the hollow region 56 (see also Figure 9).

The members 25 will be similar to the Figure 4 arrangement but the aperture 34 will not be required and the chip capacitors 28 will be located nearer to the hole 32. As shown in Figure 8 a notch 57 provided on each side of member 57 provides a positive locating arrangement in combination with the web 58 of the moulded body portion 41 (see Figure 7).

Claims (17)

1. A*plug for use in line verification for pre-cut-over testing of telecommunications switching apparatus, said plug comprising: a body of electrically insulating material; two elongate connector means extending from said body, said connector means each comprising two opposed conductive layers separated by a layer of electrically insulating material and capacitive means provided thereon to a.c. couple the conductive layers.

2. A plug as claimed in claim 1 wherein the body includes means for retaining a withdrawal cord or the like.

3. A plug as claimed in claim 1 wherein the retaining means comprises an aperture in the body.

4. A plug as claimed in claim 1, 2 or 3 wherein the body includes insulated members extending therefrom to aid location in use.

5. A plug as claimed in claim 4 wherein the members comprise two substantially cylindrical portions of the body.

6. A plug as claimed in any one of claims 1 to 5, wherein the capacitive means comprises a chip type capacitor, surface mounted on spaced portions of one of said conductive layers so as to interconnect said portions.

7. A plug as claimed in claim 6 wherein a hole is provided through the conductive and insulating layers of said connector means and conductive means are provided through the hole to electrically connect part of the conductive layers separated by the insulating layer.

8. A plug as claimed in any one of claims 1 to 7 wherein the body includes a channel for receiving the elongate connector means and holding means are provided to retain them within the body.

9. A plug as claimed in claim 8 wherein the holding means includes an aperture in said connector means.

10. A plug as claimed in claim 9 wherein the holding means includes a lug provided on the body for co-operating with the aperture.

11. A plug is claimed in claim 9 wherein the holding means includes an insulated pin passing through the body and said aperture and is deformable to retain the connector means in position.

12. A plug as claimed in any one of claims 1 to 8 wherein the body comprises of two part interlockable body.

13. A plug as claimed in claim 12 including resilient locking members in one part of the body co-operating with an aperture in the other part of the body.

14. A plug as claimed in any proceeding claim including extensions in the four corners of the body to support the connector means in at least one plane.

15. A plug as claimed in any preceding claim including an aperture for receiving and protecting the capacitor means on each said connector means.

16. A plug for use in line verification substantially s described herein and with reference to Figure 2 to 6 of the accompanying drawings.

17. A plug for use in line verification substantially as described herein and with reference to Figure 7 to 9 of the accompanying drawings.