GB2460480A

GB2460480A - Signal treatment device for use with telecommunications equipment

Info

Publication number: GB2460480A
Application number: GB0818746A
Authority: GB
Inventors: John Andrew Warren
Original assignee: British Telecommunications PLC
Current assignee: British Telecommunications PLC
Priority date: 2007-07-27
Filing date: 2008-10-13
Publication date: 2009-12-02
Also published as: GB0818746D0

Abstract

A signal treatment device 40 comprising: a plate having a front face (41, fig.5), a rear face and an aperture 44 for a wire to pass through the plate; a first telephone cable connection means 45 mounted on the plate and having terminals for releasable electrical connection to a rear-side telephone cable; a second telephone cable connection means 47 mounted on the plate and having terminals for releasable electrical connection to a front-side telephone cable; and signal treating means (46, fig.5), such as a low pass filter, electrically connected to the first and second telephone cable connection means; there is a gap 48 in the periphery of the plate around the aperture to enable wires 50 to enter the aperture 44 and pass through the plate. In use the signal treatment device may be retrofitted to an existing network termination box by removing an existing front plate 16, passing existing wires 50 through wire guide opening 48 of aperture 44, plugging the device 40 into an existing back plate 12 via plug and jacks 45, 15, and connecting the existing front plate 46 to the front of the signal device by connectors 17, 47.

Description

DEVICE FOR USE WITH TELECOMMUNICATIONS EQUIPMENT

Technical Field

The present invention relates to telecommunications equipment such as network termination equipment for connecting telecommunications apparatus such as telephones, fax machines, computer modems etc. to a telecommunications network. In particular, the present invention relates to additional devices such as filters and other signal treatment devices for use in association with network termination equipment.

Background to the Invention

A network termination device is a device connecting an end-user's or customer's data or telephone network and equipment to a local exchange carrier's line, It generally provides the physical point of termination of an incoming (generally two-wire) line from a carrier's network into a customer's premises, and usually also provides the legal demarcation point between the external (carrier's) network and the customer's internal network.

Figures 1 and 2 show representations of a standard network termination device (such as an NTE5 network termination device) in unexploded form (Figure 1) and in exploded form (Figure 2). With reference primarily to Figure 2, the device 10 comprises a back-box 12, a back-plate 14 and a front-plate 16. The back-box 12 may be attached to an interior wall (not shown) of a room within a customer's premises, and when in use, a local exchange carrier's telecommunications line would enter the customer's premises and enter the back-box 12 via an aperture 11 or elsewhere, then pass through the back-plate 14 by means of a male cable connector 17 mounted on the front-plate 16 engaging with a female cable connector 15 mounted on the back-plate 14. The line would then be electrically-connected to a socket 18 in the front-plate 16 into which a customer's cable connector (not shown) for a telephone line may be inserted. (It will be noted that since Figure 2 shows the network termination device in exploded from, the female cable connector 15 appears as two separated parts, namely an aperture 15a and a socket 15b, but it will be understood that once assembled, these two components function as a single component, namely a female cable connector 15.) When the network termination device 10 is in use, it may be linked to the external (carrier's) network and to other devices such as extension sockets by wires 19 (shown in Figure 1), which may be passed through one or more apertures 11 in the back-box 12. Any extension wiring may be electrically and physically connected to the back of the front-plate 16 by means of IDC (Insulation Displacement Connector) terminals or screw terminals for example.

As well as the electrical terminals of female cable connector 15, additional circuitry may be located within a housing 13 located within or next to the back-plate 14. For example, network termination devices may contain a lightning protection device or surge protector which would generally be located across the incoming line, line test circuitry, and other components.

Also, with telecommunications networks in some parts of the world, for example countries within the United Kingdom, a third wire, known as the bell' wire, is used to carry a ringing signal around the extension wiring of a user's local or home premises. Network termination devices generally contain components or circuitry (generally one or more capacitors and resistors) to de-couple common mode ringing signals from the line. These components may also be located within the housing 13.

Over the last few years, it has become increasingly common for end-users to use their existing connection to the external telecommunications network not just for voice telephone calls but also for Internet access. This can be achieved using an analogue or voice-band modem, but this is increasingly commonly being achieved using Asymmetric Digital Subscriber Line (ADSL) technology or other types of Digital Subscriber Line (DSL) technology commonly referred to with the umbrella term "broadband", all of which generally enable faster data transmission over copper telephone line twisted pairs' than voice-band modems have been able to provide.

A problem with DSL implementation is that there may be interference between DSL carrying wires and various radio-frequency (RF) systems. Twisted-pair wire is particularly prone to picking up interference signals from external RF sources.

As will be explained below, the third bell wire' in use with most home extension wiring (in the UK at least) can cause problems for ADSL under certain conditions, as a number of possible effects may combine to increase the overall level of noise on the line. This increase in noise may reduce bit-rate and cause problems with line stability. While most homes with a bell wire and having some extension wiring will suffer from such problems to some extent, possibly to a significant extent, it is known that simple, low-cost filtering components added at the network termination device can significantly reduce this effect throughout the home network.

A balanced DSL loop comprising a twisted wire pair generally carries both differential and common mode currents. The differential currents carry the information signal, and the common mode currents are typically associated with noise due to RF interference.

One of the possible effects referred to above is that the third bell' wire can itself upset the balance of an ADSL carrying pair. Most external noise is picked up in the ADSL pair in the common mode. If it stays in this mode then it does not necessarily present a problem to the ADSL system since its signal appears across the pair in the differential mode. However, because of the poor balance of the ADSL pair caused by the third wire effect there may be significant common mode to differential mode conversion and therefore the noise may be converted into the differential mode, which may cause a problem to the ADS[ system.

Another of the possible effects referred to above is that the third wire can also act as an antenna picking up interference which couples directly into the ADSL carrying pair as noise.

Figure 3 illustrates the possible interference between the bell wire and an ADSL carrying pair within an extension wiring portion of internal wiring in a home, the wiring extending from a standard network termination device 10 towards an extension point (not shown).

A known solution to the above problems is to include a simple low pass filter in line with the third bell' wire which effectively isolates it from the ADSL carrying pair at ADSL frequencies.

This may improve the balance of the ADSL pair and reduce the amount of interference that is coupled into it, thereby improving the performance of the system. Figure 4 illustrates the layout of electrical components suitable for such a filter, where the numbers 2 to 5 indicate the pin numbers generally used on telephone cable connectors in the UK. Pins 2 and 5 are generally used for the telephone line itself, pin 3 is used for the bell wire, and pins 1 (not shown), 4 and 6 (not shown) are not used. The two filtering components shown in Figure 4 are a common mode choke (for example a BT8OA-RF3) which sits across the incoming line (pins 2 and 5) and a 22mH inductor which is in line with the bell wire.

It is generally necessary for such a filter to be fitted between the back-box and the front-plate of a network termination device. It is now possible for network termination devices to be manufactured with suitable filter components already included, but for network termination devices without suitable filter components already fitted and in use, it is desirable to incorporate suitable filter components into the existing network termination device without completely replacing it. Previous versions of network termination device bell wire filters have therefore been incorporated into or mounted next to a revised front-plate. With such a design, the existing front-plate must therefore be physically disconnected from the back-plate and a new or modified front-plate including a filter section connected in its place.

A difficulty with the above procedure may become apparent where there is additional wiring leading from the network termination device to one or more extension points within the premises. Referring again to Figure 2, any extension wiring is generally electrically connected to terminals mounted on the back of the front-plate 16, and passes from there through a conduit in the back-plate 14 to the back-box 12, from where it emerges and runs to the or each extension point. For the front-plate 16 to be removed and replaced with a new front-plate incorporating filter components, it is therefore necessary for any extension wiring connected to the back of the old front-plate 16 to be removed and reconnected to the back of the new or modified front-plate. With existing filter adaptors, the process therefore involves disconnecting the extension wiring from the back of the front-plate 16 then feeding the disconnected end of the extension wiring through a central conduit of the filter adaptor. The extension wiring then needs to be reconnected once the filter adaptor has been put in place.

In either situation, this disconnection and reconnection of extension wiring may not be a simple operation for end-users to complete themselves, so a telecommunications engineer is generally required to perform the task, which can introduce time delays, inconvenience and additional costs into the procedure.

Similar problems may be encountered in other situations where it is desired to incorporate or retro-fit' filtering devices or other types of signal treatment device into or in association with existing telecommunications or other equipment having existing wiring such as extension wiring, power leads, or other such wiring for example.

Summary of the Invention

According to the present invention, there is provided a signal treatment device, the device comprising: a plate having a front face, a rear face and a conduit for a wire to pass through the plate; a first telephone cable connection means mounted on the plate and having terminals for releasable electrical connection to a rear-side telephone cable; a second telephone cable connection means mounted on the plate and having terminals for releasable electrical connection to a front-side telephone cable; and signal treating means electrically connected to the first and second telephone cable connection means; said conduit being open such that a telephone wire having an end on each side of the plate can, without either end of the wire being passed through the conduit, be inserted into the conduit such that the wire runs through the conduit only once.

Preferred embodiments of the invention are capable of resolving problems surrounding the prior art discussed in detail above by allowing for an interstitial plate comprising suitable filtering means to be introduced between the existing back-box and front-plate of an existing network termination device while making disconnection and reconnection of any extension wiring unnecessary. Instead of needing to disconnect the extension wiring from the back of the old front-plate then reconnect it to the back of a new front-plate or to the back of a modified front-plate once the wiring has been fed through the conduit of a filter section, it is possible for an interstitial plate comprising suitable filtering components to be introduced between the back-box and existing front-plate without the need to disconnect the extension wiring from the back of the old front-plate, because the interstitial plate contains a slot or opening into the conduit through which the still-connected extension wiring may be passed.

It will be understood that the plate' need not be a simple flat structure, and the front and rear faces need not be planar; their respective shapes may depend on the required functionality of the device and the shape of any equipment with which the device is to co-operate.

Where the device is intended for use in association with equipment having wiring running in the general direction from the front to the rear face of the plate, the conduit would generally extend from the front face to the rear face of the plate. Other layouts are possible however.

The conduit is preferably open on account of an aperture in a lateral face of the plate, the aperture preferably extending from the front face to the rear face of the plate.

The first telephone cable connection means may comprise a male connector and the second may comprise a female connector. The reverse of this or other combinations or types of connector may also be applicable in some situations however.

Preferably the first and second telephone cable connection means are arranged such that the device may be interposed between a pair of opposing co-operating connectors, such as the male and female cable connectors of existing network termination equipment for example. In this case, suitably compatible and suitably located first and second telephone cable connection means allow for the device to be inserted easily into position between the corresponding connectors of the existing equipment.

The signal treating means may comprise signal filtering means, such as means for substantially isolating a bell wire from a pair of wires carrying an ADSL signal at ADSL frequencies. In particular the signal treating means may comprise a low-pass filter. Other types of signal treating means are possible however.

Brief Description of the Drawings

Preferred embodiments of the present invention will now be described with reference to the appended drawings, in which: Figure 1 shows a standard network termination device in unexploded form; Figure 2 shows a standard network termination device in exploded form; Figure 3 illustrates possible interference between a bell wire and an ADSL carrying pair; Figure 4 illustrates the layout of electrical components suitable for a bell wire filter; Figure 5 shows the components of a filter device according to a preferred embodiment of the invention; and Figure 6 shows a filter device according to a preferred embodiment of the invention being located within an existing network termination device.

Description of the Embodiments

With reference to Figure 5, there is shown a filter device 40 according to a preferred embodiment of the invention. The filter device is essentially in the form of a plate having front face 41, a rear face 42 and a conduit 44 through which wiring such as extension wiring may pass from one side of the filter device to the other. A male telephone cable connector 45 is mounted on the plate such that its terminals protrude from the rear face 42. A corresponding female telephone cable connector 47 is mounted on the plate such that its terminals are accessible from the front face 41. Filtering components 46 suitable for bell wire filtering (such as those shown in Figure 4 for example) are mounted on the plate and are electrically connected to the terminals of the male and female cable connectors.

A filter component 46 such as that shown in Figure 5 may contain just the two filtering components shown in Figure 4, namely a common mode choke which sits across the incoming line (pins 2 and 5) and an inductor (22niH, for example) in line with the bell wire.

Where the line carries an ADSL signal, the common mode choke acts to reduce (i.e. filter) the amount of common mode noise on the line whilst having very little effect on the ADSL signal which appears in the differential mode. The 22mH inductor acts as a simple low pass filter which passes the low frequency ringing signal onto the third bell wire, but blocks the majority of the higher frequency ADSL signal from passing through. This effectively isolates the third bell wire from the ADSL carrying pair and minimises the effect that this causes.

It will be noted that due to a slot 48 extending from the front face 41 to the rear face 42, the conduit 44 is "open", in the sense that it does not completely enclose any wiring passing through the conduit. It will be understood that by virtue of this slot, a wire having one end physically and electrically connected at a point on the front side of the plate and its other end physically and electrically connected at a point on the rear side of the plate may be passed into and out of the conduit, and therefore need not be threaded' through the conduit.

Referring now to Figure 6, this shows a filter device 40 such as that shown in Figure 5, and a network termination device 10 such as that described with reference to Figures 1 and 2. Of the principal components of the network termination device 10, the back-box 12 and back-plate 14' are shown mounted together, as would normally be the case if the network termination device 10 is in use. Housing 13 and any circuitry located within this are not shown as they would not be readily visible once the network termination device 10 is in use.

The front-plate 16, which would usually be held by screws (not shown) to the back-plate 14, is shown detached from the back-plate 14. It will be noted, however, that some extension wiring 50 is shown still attached to the back of the front-plate 16, from where it passes through the back-plate 14 and into the back-box 12, eventually emerging as cable 19.

From the position shown in Figure 6, it will be understood that filter device 40 may be positioned approximately between the back-plate 14 and the front-plate 16. The extension wiring 50 may then be passed into the conduit via the slot 48. The filter device 40, the back-plate 14 and the front-plate 16 may then be brought together such that the male cable connector 45 of the filter device 40 engages with the female cable connector 15 of the back-plate 14, and such that the male cable connector 17 of the front-plate 16 engages with the female cable connector 47 of the filter device 40. This is of course possible if both male cable connectors 17 and 45 are compatible with both female cable connectors 15 and 47. The front-plate 16 may then be re-secured by screws (not shown) to the filter device 40 and the back-plate 14. Due to any increase in the distance between the front-plate 16 and the back-plate 14 required to accommodate the filter device 40, the screws may need to be longer than those previously sufficient to secure the front-plate 16 directly to the back-plate 14.

The telecommunication link between the external network and the socket 18 may thus be restored via the filter device 40, which acts partly as a shunt between the back-plate 14 and the front-plate 16 while also including suitable filtering components in the circuit for reducing or removing interference problems caused by the presence of a bell wire. The presence of the slot 48 allows the whole process to be completed without disconnecting the wiring 50.

While the slot 48 may be wider or narrower than that shown in Figures 5 and 6, and the shape and size thereof may need to be selected depending on the type of equipment with which the filter device is intended to be used, it will be apparent that in the example given, it is preferable for the slot to be sufficiently wide as to enable extension wiring to be passed into the conduit reasonably easily, while not so wide as to allow easy access into the network termination device once this has been reassembled with the filter device in place. An overly-wide slot may be unsightly, may allow water, dust or other unwanted materials to enter the network termination device too easily, or may allow people such as young children to insert their fingers into the device, possibly damaging the internal components of the device or injuring themselves. As a further improvement, the device may be provided with a flap or other such means for completely closing the slot once the device has been installed.

The preferred embodiment described above is one that would be suitable for use with a standard network termination device such as an NTE5 network termination device, in particular where extension wiring runs from the network termination device to one or more extension points. It will be understood that alternative embodiments may be suitable for use with other types of network termination device, such as those with one or more additional sockets on their front-plates for connection to other devices. Further embodiments may be suitable for use with other types of telecommunications equipment, such as extension sockets, for example.

The preferred embodiment described above is one that would be suitable for providing a signal-filtering function when used in association with existing telecommunications equipment such as network termination equipment, and in particular when used in conjunction with an internal network having a pair of wires being used for ADSL internet access, and a third bell' wire. It will be understood that alternative embodiments may be suitable for providing other types of signal treatment functions in other situations however.

Claims

CLAIMS1) A signal treatment device, the device comprising: a plate having a front face, a rear face and a conduit for a wire to pass through the plate; a first telephone cable connection means mounted on the plate and having terminals for releasable electrical connection to a rear-side telephone cable; a second telephone cable connection means mounted on the plate and having terminals for releasable electrical connection to a front-side telephone cable; and signal treating means electrically connected to the first and second telephone cable connection means; said conduit being open such that a telephone wire having an end on each side of the plate can, without either end of the wire being passed through the conduit, be inserted into the conduit such that the wire runs through the conduit only once.
2) A signal treatment device according to claim 1, wherein said conduit extends from the front face to the rear face of the plate.
3) A signal treatment device according to claim 1 or 2, wherein said conduit is open on account of an aperture in a lateral face of the plate, said aperture extending from the front face to the rear face of the plate.
4) A signal treatment device according to any of the preceding claims, wherein said first telephone cable connection means comprises a male connector.
5) A signal treatment device according to any of the preceding claims, wherein said second telephone cable connection means comprises a female connector.
6) A signal treatment device according to any of the preceding claims, wherein said first telephone cable connection means and said second telephone cable connection means are arranged such that the device may be interposed between a pair of opposing co-operating connectors.
7) A signal treatment device according to any of the preceding claims, wherein said signal treating means comprises signal filtering means.
8) A signal treatment device according to any of the preceding claims, wherein said signal treating means comprises means for substantially isolating a bell wire from a pair of wires carrying an ADSL signal at ADSL frequencies.
9) A signal treatment device according to any of the preceding claims, wherein said signal treating means comprises a low-pass filter.
10) A signal treatment device substantially as described herein, with reference to the accompanying drawings.
11) A method of installing a signal treatment device according to any of claims 1 to 10 in association with a network termination device and at least one telephone wire, said network termination device comprising a back-box and a front-plate, said back-box having terminals for releasable electrical connection to a rear-side telephone cable and a cable connector releasably engaged with a cable connector of said front-plate, and said front-plate having terminals for releasable electrical connection to a front-side telephone cable and a cable connector releasably engaged with a cable connector of said back-box, said telephone wire being electrically and physically connected to the front-plate and extending through an aperture in the back-box, said method comprising: disengaging the cable connector of said front-plate from the cable connector of said back-box; positioning the signal treatment device between the back-box and the front-plate; inserting the telephone wire into the conduit without passing either end of the telephone wire through the conduit; engaging the cable connector of said front-plate with one of said first and second telephone cable connection means of said signal treatment device; and engaging the cable connector of said back-box with the other of said first and second telephone cable connection means of said signal treatment device.