Abstract:
The invention provides a plug ( 100 ) which is adapted to be connected to a cable, such as an Ethernet cable, the plug ( 100 ) having a generally rectangular cross section and being dimensioned and arranged to be received by an aperture in a socket. On opposite lateral faces of the plug a region, or layer, of conductive material ( 24, 26 ) is provided for the transmission of electrical current to/from the cable. Use of the invention therefore permits cabling that has conventionally been used to supply data to also supply power, typically in excess of 200 Watts or so. Such amounts of power are sufficient for operating most equipment that also requires a data connection.

Description:
BACKGROUND 
     This invention relates to a plug for data transmission and/or power supply, and to a socket for insertion of a plug therein. 
     There are a number of different plug-in connectors that the invention is applicable to, including, but not limited to Ethernet type connectors and USB connectors. Note that the Ethernet connection method as described above commonly uses a standard 8P8C connector which is loosely but erroneously called by the data communications industry an ‘RJ45’. RJ45 in fact describes a rarely used keyed variant of 8P2C with a special wiring arrangement for a telephone application. 
     PRIOR ART 
     It is known from DE-A-10053843 (Siemens AG) to provide an Ethernet plug-in connector with independent contact elements for providing a voltage supply. In this invention, the voltage supply is provided by contacts located on an outside surface of the socket. Thus, the corresponding plug requires an additional connector to connect with the voltage supply. A problem with this is that both the plug and socket are enlarged so are no longer interchangeable with existing equipment and the cost of manufacturing the extra elements is significant. 
     A further development is disclosed in WO-A1-02067387 (Siemens AG) which provides a power supply whilst maintaining a standard plug and socket design. Two pairs of co-operating connectors are provided on the connecting faces of the plug and socket. These power connectors are designed in the same manner as the data connectors i.e. a groove in the plug accepts an outwardly extending spring contact provided in the socket on insertion of the plug therein. 
     Although this improvement provides a reduction in cost compared to the earlier advance, full interchangeability between the new sockets and existing plugs is not provided due to the provision of the extra spring contacts for which no corresponding groove is provided in existing plugs. Thus complete insertion of an existing plug with a new socket is not achievable so may result in a loose connection. 
     U.S. Pat. No. 4,869,677 (Teradyne Inc) describes a two-part connector which provides an electrical connection between a backplane printed circuit board (PCB) and a daughter ‘PCB’, through which power may be transmitted. One part of the connector carries a contact on one side wall, and another part of the connector carries a corresponding contact on a facing outside wall. 
     It is known to incorporate two opposing pairs of contacts into a plug or socket for purposes other than power provision. For example, such devices are described in U.S. Pat. No. 4,813,890 (Siemens AG), U.S. Pat. No. 5,415,570 (AT&amp;T) and EP 0 891 017 (Framatome), which all disclose pairs of contacts providing electrical shielding. 
     The device in U.S. Pat. No. 5,415,570 (AT&amp;T) provides data connections and the arrangement shown in U.S. Pat. No. 5,356,300 (The Whittaker Corporation) describes pairs of contacts that are used as ground contacts. 
     Some examples of uses of universal serial bus (USB) connectors include: wireless Internet access and printer connections. Whilst these provide the required speed that a user expects, there can be issues with the security of such technology and interference from other wireless networks in the local area. There have also been health related concerns raised about the use of wireless technology due to a possible increase in electro-magnetic radiation of such systems. 
     Hence, one object of the invention is to provide an acceptable alternative to the use of these wireless technologies by providing a reliable and acceptable rate of data transfer using the existing Ethernet port position provided on the equipment but fitting the connector with power and/or optical data capability within the cabling between the different pieces of equipment. 
     An aim of the present invention is to provide a plug and socket or plug-in connector which may be deliberately non interchangeable with existing standard plugs and sockets, and which may have at least one form of connectivity between the plug and socket. 
     Another aim of the invention is to provide a connector system for use intermediate an external environment and a user interface for the purposes of acting to distribute power and data. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention there is provided a plug which is adapted to be connected to a cable, the plug having a generally rectangular cross section and being dimensioned and arranged to be received by an aperture in a socket, characterised in that on opposite (lateral) faces of the plug a region, or layer, of conductive material is provided for the transmission of electrical current to/from the cable. 
     As generally, in use, plugs are connected to cables, it is understood that the invention includes a plug in combination with a length of cable. 
     Use of the invention therefore permits cabling, that has conventionally been used to supply data, to also supply power, typically in excess of 200 Watts or so. Such amounts of power are sufficient for operating most equipment that also requires a data connection. 
     In addition, optionally the invention provides a plug and socket, or plug-in connector, which is interchangeable with existing standard plugs and sockets, having at least one form of connectivity between the plug and socket. However, in such an arrangement additional circuitry is provided so as to prevent inadvertent shorts or unwanted power transmission and to protect against overload. 
     Ideally the plug has a conductive material for conducting an electric current capable of carrying in excess of 3 Amps of current, preferably in excess of 5 Amps of current and most preferably in excess of 10 Amps of current. 
     In addition the plug and ancillary and the conductive material may be rated to conduct an electric current capable of supplying in excess of 50 Watts of power, preferably in excess of 200 Watts of power and most preferably in excess of 500 Watts of power. 
     It is thus appreciated that use of the invention in its broadest sense enables a domestic user to effectively devise a single ‘backbone’ of cabling and to site or locate plugs peripheral or indeed a myriad devices at any point on the cable without the need to be concerned with a nearby power supply, for example in which to plug a transformer for powering the peripheral device and—importantly—without the clutter of different cables and accessories. 
     The Universal Serial Bus (USB) is considered a short haul (1 to 3 meters) format for computer interfacing. A conventional connection arrangement designated as a USB connector already incorporates a limited power 5 Volt power supply facility as part of its specification and design. Optical communication may be included into this format by including the fibre within the tongue that supports the electrical conductors. 
     In a preferred embodiment the plug includes a support for at least one optical communication cable, which is advantageously formed from a polymer. 
     Thus in this preferred embodiment of the plug it is understood that because the system is only intended for relatively small installations, it is well suited as a very broadband data carrier and is typically able to operate in excess of several hundred Mega Baud (MBits/sec) to data rates in excess of 1 Giga Baud (GBits/sec) and therefore offers the advantages of an optical data network. 
     Ideally the optical fibre data cable in the optical data network is a Plastic Optical Fibre (POE). In addition the optical data network distribution system includes a pair of copper cables to form a hybrid cable. 
     The optical data network may be adapted to be located so that it couples with a distribution device such as a wall plate, which may have one or more sockets, such as an Ethernet socket and/or a power socket. 
     Alternately the modular optical data network may be adapted to connect with a telecommunications plug or socket. This may be practically achieved by way of a transponder adapted for example to convert one form of digital signal into for example an optical signal. 
     Other peripheral devices may be connected directly to the optical data network. Examples of these are: a wireless data transmitter/receiver device, such as a Bluetooth (Trade Mark) transceiver or an infra red data transmitter/receiver device or an encoder suitable for converting one signal into another. Other examples of devices include: amplifiers, filters, switches and timers, such as for example a timer can be connected to the network and control other items connected to the bus. 
     A further feature of the invention is that it may be connected directly to electrical generating devices such as solar panels or windmills/wind turbines, so that in the event of a power failure, or for example when in remote locations, it is still possible to operate basic devices such a personal computer, laptop or other devices. 
     The two way nature of the power connection of the socket may for example be used in an emergency to allow the internal battery of a laptop to power the system in reverse. 
     According to a second aspect of the invention there is provided a socket having an aperture which opens to receive a plug, there being a plurality of contacts dimensioned and arranged to receive signals from one or more data channels, characterised in that (lateral) regions of the socket have conductive regions adapted to contact the plug and thereby conduct an electric current. 
     So as to cooperate with the conductive lateral regions of the plug, the conductive regions in the socket are ideally disposed on opposite faces, supported within the socket, so that they are presented to contact the conductive material provided on lateral regions of the plug. 
     Ideally shutters, covers or some other displaceable means is provided on the, or each, conductive region(s) so as to prevent any inadvertent shorting (short circuit) across the opposite faces, supported within the socket. 
     Ideally the conductive regions of the plug and/or socket, if exposed, are electrically isolated from the power available when a legitimate plug is not fully inserted into a legitimate mating socket. 
     Ideally the conductive material for conducting an electric current that are formed as lateral regions on the plug are capable of carrying in excess of 3 Amps of current, preferably in excess of 5 Amps of current and most preferably in excess of 10 Amps of current. 
     Accordingly the present invention also provides a connector comprising: a socket having an aperture which opens against a plug-in direction (Z) and comprises a plurality of contacts characterised in that lateral regions of the plug support conductive material for transmitting an electric current. 
     Ideally at least a second pair of contacts is provided within the aperture wherein the second pair of contacts is capable of providing a power supply or a data connection. 
     In addition the present invention provides a connector comprising a plug of particular dimensions and having a plurality of outwardly projecting portions which project around the connector and/or towards a plug-in direction (Z) the body and outwardly projecting pip is shaped and dimensioned so as to prevent insertion of the plug into a conventional 8P8C—or similar—socket. This is important because inadvertent insertion of the plug, according to the invention, into an existing 8P8C type socket could result in an earth short or an unintended transfer of a large amount of power to components or a system, not intended or capable of handling large currents, and thus the body shape and pip prevents this from occurring and any ensuing damage. It being understood that inadvertent insertion of existing types of 8P8C plugs into a socket according to the invention would not lead to any damage as lateral surfaces of existing 8P8C plugs are formed from an insulation material. 
     The pip preferably takes the form of a raised projection, from the plug, having a rectangular cross section that is typically between 5.0 mm and 5.3 mm long and between 0.7 mm and 1.0 mm high. 
     Alternatively, or in addition to, the body of the plug is adapted to be bigger than bodies of existing 8P8C plugs, thereby rendering the possibility of insertion of the plug into a 8P8C socket impossible. 
     Also of significant importance is that the unique keying of the plug and socket minimises customer confusion by preventing mating of non matching arrangements. 
     Alternatively the plug and/or socket can be made with the minimum or maximum dimensions in such a way that it fits all variants in the same manner as a master key opens all doors in a hotel and the individual keys open individual rooms only. 
     A third embodiment of the invention provides a connector comprising a socket having an aperture which opens against a plug-in direction (Z) and comprises a plurality of contacts and a corresponding plug having an outwardly projecting portion which projects towards a plug-in direction (Z) the outwardly projecting portion comprising a plurality of first contacts wherein the contacts co-operate with the first contacts on insertion of the plug into the socket characterised in that at least a second pair of co-operating contacts is provided within the aperture of the socket and on the outwardly projecting portion of the plug wherein the second pair of co-operating contacts provides a power supply or a data connection on insertion of the plug into the socket. 
     Ideally the second pair of co-operating contacts provides a power supply and are disposed on lateral; faces or sides of the plug. Respective electrical contacts are provided in the plug. 
     A data connection includes an optical connection whereby an optical fibre is connectable and a programming connection, for example enabling data I2C programming. 
     The invention may be embodied in a 10P10C connector providing data and power in the cat-5 Ethernet environment. In such an embodiment the middle 8 contacts may be standard cat-5 contacts (i.e. for data transmission), and the outer 2 contacts may provide a power supply, e.g. a 48 volt supply. Such an arrangement may have the advantage that it is possible to insert a 10 contact plug according to the invention into a standard 8 contact (8P8C) socket, so that the middle 8 contacts provide a data connection while the outer 2 contacts are inactive. Similarly, it is possible to insert a standard 8 contact (8P8C) plug into a 10 contact socket according to the invention. 
     Moreover, the invention may be incorporated in firstly the ‘service provider side’ of the PDX (Power and Data eXchange) in order that the PDX can send power upstream to power any device required by the service provider, such as an ADSL device, that is plugged into it and secondly in the ‘customer side’ of a wall-port in order that the PDX unit via the wallport can provide data, control and power out of the wallports in order to send power and data to any device, such as a computer, which is plugged into that wall-port. The invention may be embodied as a connector providing a connection between the PDX unit and each of a plurality of wall-ports, or a connection between two or more wall-ports. 
     For the avoidance of doubt the term wall-port is intended to include any device, typically recessed flush with a wall, that is capable of acting as an interface and in use is connected to a PDX unit, by way of a hybrid cable, and provides an inlet (usually via a front plate) for power and data, to equipment and peripherals such as: computers, printers telephones, IP enabled devices, televisions and all other telecommunication equipment. 
     The invention will now be described by example and with reference to the accompanying drawings, of which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a socket of a connector according to the invention; 
         FIG. 2  shows a plug according to the invention adapted to be received by the socket described in  FIG. 1 ; 
         FIGS. 3A ,  3 B and  3 C show cross-sections through an alternative plug inserted in a socket; 
         FIG. 4  shows schematically the end of the outwardly projecting portion of the alternative plug of  FIGS. 3A ,  3 B and  3 C; 
         FIG. 5A  shows one embodiment of a power circuit isolator on a plug 
         FIG. 5B  shows the embodiment of a power circuit isolator on a plug in  FIG. 5B  inserted in a socket with the sprung contacts connected to electrical contacts in the socket; 
         FIG. 6  shows one embodiment of a shroud to protect exposed conductors on a plug when not inserted into a mating socket; 
         FIG. 7  shows one embodiment of a power circuit isolator on a socket; 
         FIG. 8  shows an alternative embodiment of lateral power circuit contacts of reduced length in socket and shrouded by plug moulding; 
         FIG. 9  shows an optical lens option for lower loss; 
         FIG. 10  shows a position for refractive index matching material; 
         FIG. 11  shows a detail of one embodiment of retainer for optical fibre to ensure positive pressure between light transmission elements in the plug and socket; 
         FIG. 12  shows a combined fibre and conductor option; 
         FIG. 13  shows an alternative fibre arrangement to avoid crossover issues; 
         FIG. 14  shows a plug option to achieve keying; and 
         FIG. 15  shows a plug option with master keying function. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a socket  2  of an example of one type of connector according to one aspect of the invention. A plug-in area or aperture  6  of the socket is provided which opens against a plug-in direction (Z). A plurality of contact springs  4  disposed in a row next to each other are provided within the aperture  6 ; the contact springs  4  form an inclined surface  8  projecting into the aperture  6 . A second pair of contacts  20 ,  22  is provided within the aperture  6  of the socket  2 . In this example, the second pair of contacts  20 ,  22  are disposed one on each of two opposite walls of the aperture  6  and consist of a metal strip to provide a power connection from the socket. An additional pair of contacts  30 ,  32  comprising optical fibre connectors is provided within the aperture  6  on the upper surface  12  of the aperture  6 . 
     The second pair of contacts  20 ,  22  for providing power can be located on any internal surface of the aperture  6  providing that the function of any existing features (such as the contact springs  4 ) is not impaired and that the two contacts are sufficiently separated that there is no chance of a short circuit so enabling the socket to receive existing cat 5 type plugs and preventing inadvertent use of the plug in a conventional socket. A person skilled in the art would appreciate these limitations. 
     The additional pair of contacts  30 ,  32  for providing an optical connection are locatable anywhere within the aperture that does not impact the insertion of a plug into the socket or interfere with any of the other connectors or features provided on a standard plug and socket connector of this type, e.g. an Ethernet or USB connector. 
     The socket may be provided with a recess  10  for engaging a corresponding protuberance on a plug. One reason for such a protuberance is to ensure that the plug can only be inserted in one orientation. 
       FIG. 2  shows a plug  100  of a connector according to the invention. The plug  100  has an outwardly projecting portion  110  comprising an initially inserted face  112  which is the face that is inserted initially into a socket when a connection between a plug and socket is made. The initially inserted face  112  includes a plurality of grooves  114  disposed in a row next to each other. These grooves  114  co-operate with the contact springs  4  provided within the socket  2 . 
     A second pair of contacts  24 ,  26  is provided one on each of opposite sidewalls  116 , 118  of the outwardly projecting portion  100  and consist of a strip of conductive material. This second pair of contacts  24 ,  26  co-operates with the second pair of contacts  20 ,  22  of the socket  2  on insertion of the plug into the socket and provides a power connection between the plug  100  and socket  2 . A third pair of contacts  34 ,  36  is also provided on the upper surface  120  of the outwardly projecting portion and consists of optical fibre connectors. This third pair of contacts  34 ,  36  is for providing an optical connection between the plug and the socket when the plug is inserted in the socket, by contacting the additional pair of contacts  30 ,  32  of the socket  2 . 
     It should be noted that although the contact springs  4  and grooves  114  co-operate with each other when the plug is inserted into the socket, there does not need to be an equal number of the contact springs and grooves. Additionally the exact location of the second and third pairs of contacts is unimportant as long as the existing functionality of the plug and socket is not compromised. The skilled person will appreciate that a number of configurations are available. 
       FIGS. 3A ,  3 B,  3 C and  4  show an alternate plug and socket connector according to the invention.  FIGS. 3A to 3C  show a plug  300  inserted into the aperture  308  of a socket  302  and  FIG. 4  shows schematically the end or initially inserted face  312  of an outwardly projecting portion  310  of the plug  300 . 
     In this example, the socket  302  ( FIGS. 3A-C ) includes a transmitter (Tx) and receiver (Rx) which are hard wired  350  to a further device (not shown). First connections  304 ,  306  between the transmitter (Tx) and receiver (Rx) and corresponding optical fibre connections  314 ,  316  of a plug  300  are provided in an aperture  308  of the socket  302 . A second pair of connectors  320 ,  322  comprising a conductive strip is provided one located on each of two opposite walls of the aperture  308  in the socket  302 . 
     Mating parts are connectors  324 ,  326  on opposite faces of the plug  300 . A third set of contacts  328  on the plug  300  relate to a set of contacts  338  in the socket  302 . This third set of contacts  328  is physically equivalent to those on an 8P8C connector. A fourth set of contacts  354 ,  356  are located on the opposite face to the third set of contacts. The fourth set of contacts  354 ,  356  on the plug  300  relate to a set of contacts  364 ,  366  in the socket  302 . 
     The plug  300  is adapted to be at least partially inserted within socket  302  to provide at least one connection out of the plurality of different connections and connector types available. To achieve this, the plug has a slightly narrowed part, the outwardly projecting portion  310 , which is capable of insertion into the aperture of the socket  302 . 
     Firstly, an optical connection is provided between fibres  314 ,  316  in the plug  300  and first connections  304 ,  306  in the socket  302  being the optical element of the Rx and Tx elements. Secondly a substantial power, as described above, connection is provided by the lateral metal contacts  324 ,  326  on the plug  300  and correspondingly located lateral contacts  320 ,  322  in the socket  302 . Thirdly a typical standard 8-way category  5  connection  328  (third set of contacts) is provided on plug  300 , and the connection provided by the corresponding set of contacts  338  in the socket  302 . Fourthly extra data connections are available on the same face as the polarising and locking pip. These contacts,  354 ,  356  on plug  300  and corresponding contacts  364 ,  366  in socket  302 , are available for programming or other serial communication purposes. 
     In this example, the plug  300  has an internal springy sleeve  340  which biases the optical fibre  314  or  316  towards the corresponding connection  304  or  306  in the socket  302  to provide a positive connection. 
     In this example, the second (power) connectors  320 ,  322 ,  324 ,  326  are shown as conductive i.e. metal or metallic strips which run along the plug insertion direction (Z). The exact shape and orientation of the connectors is unimportant, however, it is prudent to make one pair of the strips slightly larger than the other to allow for slightly variations in the relative locations of the plug and socket, thus ensuring a good connection. 
     A connection is available which provides an optical fibre connection between the plug and socket. This connection can be used in addition to or separately from the power connection, indeed the plugs and sockets do not necessarily have to have the same sets of connections. Two optical fibre connectors  304 ,  306  are provided in the socket  302 . When a plug  300  is inserted, these two optical fibre connectors  304 ,  306  co-operate with correspondingly located optical fibre contacts  314 ,  316  on the plug. In this example the optical fibre contacts  314 ,  316  are provided on the end face  312  of the plug and contacts  304 ,  306  on the surface of the aperture  308 , specifically the end wall  318  of the aperture  308 . 
     A fourth possible connection is also shown in  FIGS. 3A to 3C  and  4 . This further connector is, for example, data I2C programming. Two connectors  354 ,  356  are shown on the plug  300  and the corresponding connections  364 ,  366  are provided within the aperture of the socket  302  beside the polarising pip. I2C is a protocol for communications between I/Cs. The connector enables a programmer to edit, save, and program EPROMs. 
     An advantage of the invention is that it provides a completely flexible solution from the transmission of data and low power electricity. In the preferred arrangement of 8 pins (data) and two pins (power), the plug and socket system provides a hybrid cable solution that accommodates data input from a variety of sources, such as an Internet service provider, a telecommunications provider (conventional twisted copper wire) and a fibre optic source (such as broadband television service channels), as well as providing a path for power. 
     What is also noteworthy is that data is able to be transmitted and received, as the data bus in all modes (ISP, conventional twisted copper wire and optical fibre), is bidirectional so enabling voice over IP, Internet surfing, as well as interactive television, conventional voice communications and on-demand video. Furthermore, as a result of the power bus (ie as provided on pins  1  and  10 ), power can be transmitted from a domestic generator, via a domestic wall-port, to a power/data exchange and thence to a mains supply metering unit to a local grid. This facility thus provides a completely flexible solution for power and data and so permits subscribers to export locally generated electricity for sale to the grid. 
     Any data or power provided from the connections  304 ,  320 ,  322 ,  330 ,  332  and I2C connectors in the socket  302  is transferred via a cable  342  to a further plug (not shown) which may be of the same type or one that accepts only data in one format or power or any combination thereof. This further plug can be connected to a computer, printer, television, lamp or a combined data and power ring main wired into a room or a building like a hybrid of an electrical circuit and data network. Data and power can obviously also flow from a plug to a socket for example at the other end of a cable  342  at the further plug. 
     The optical fibre used for the optical connection can be glass however, for most domestic applications, a mono mode plastic cable is preferred. Firstly, as plastic cable is safer within the home and; secondly, the data transmission provided by plastic fibres is sufficiently good for most domestic uses. For distances of less than 100 m, the signal to noise ratio of plastic cable is acceptable and this length of cable is more than enough for most domestic requirements. The optical fibre can be any suitable standard optical fibre which is readily available in the market. 
     The use of an optical cable provides a higher specification data cable than conventional. An optical cable also provides a signal having a wide band of frequencies. 
     In all examples, the metal contacts  20 ,  22 ,  320 ,  322  within the socket  2 ,  302  are capable of providing power to an inserted plug  100 ,  300 . The metal contacts  20 ,  22 ,  320 ,  322  comprise metal strips or blocks of copper, a copper alloy or another good metallic conductor. The metal contacts  20 , 22 , 320 , 322  are provided on opposite sides of the aperture  6 , 308  of the socket  2 , 302  and, on insertion of a plug  100 ,  300 , correspondingly located metal portions  24 ,  26 , 324 ,  326  disposed one on each side of the outwardly protruding portion  310  of the plug  100 , 302  contact the metal contacts  20 ,  22 ,  320 ,  322 . One pair of the metal contacts or portions, preferably the pair  20 ,  22 ,  320 ,  322  provided in the socket, can be sprung such that on insertion of a plug into the socket, these contacts are flattened slightly. This ensures both a good electrical connection between the plug and the socket but also provides increased mechanical stability of the plug within the socket. 
     The power connection described in this document can provide 48 Volts without significant adaptation of the socket for safety or legislative reasons. The power provided can be used to run computers, lamps and general ring main devices such as fridges, televisions and radios i.e. low current devices. This type of connection can be used as an emergency back-up for power which advantageously can also provided emergency back-up for data in the event of a power cut or other disruptive event. The power connection can be advantageous for other reasons than those described thus far. It can supplement the power available from a USB type of connector which typically runs at 5 v, the invention enables a higher voltage capability than the USB connector enabling better connectivity between devices. 
       FIG. 4  shows an end on view of the plug  300 . The basic format of the 8P8C connector is retained with the connections  328 . The lateral power connections  324 ,  326  occupy a clear area on the 8P8C connector. There is a variant of a standard Ethernet connector that uses a screened cover. The plug and socket of the present invention, in its keyed version ( FIG. 12 ), prevents interconnection with such a standard connector. The master version ( FIG. 13 ), on the other hand, fit with such a standard connector. The power supply that is connected to the lateral power connectors  324 ,  326  is current limited to a safe value under these conditions. 
     The optical fibre is shown as  314  and  316 . The option exists to have a single fibre with a directional splitter, if required. This may be fitted within the plug or socket. It is clear that though two fibres are shown here, there is room for more fibres in this position if required. The auxiliary data connections  354 ,  356  can be used for a multiplicity of functions. In one particular application for installation of this connector in a wall plate power and data distribution system these pins are used to obtain access to the internal circuitry within the wall plate to allow for programming and routing information to be accessed and uploaded, without the need for extra connectors to be fitted to the wall plate. Other uses for this connection is as a high power USB option, other voltage supplies etc. Note that only two auxiliary data connections are shown in this area of the connector but this can be increased to about 6 or more. 
       FIG. 5A  shows one embodiment of a power circuit isolator on a plug. The side contacts  501  and  502  are electrically isolated from the cable conductor when the plug is not inserted (as illustrated in the left-hand detail in  FIG. 5A ). The side contacts  501 ,  502  are sprung so that they extend outwardly from the plug when under no external force. The action of insertion causes the side contacts  501 ,  502  to be urged inwardly towards one another so that the side contacts  501 ,  502  come into contact with electrical contacts  504 ,  506 , respectively (as illustrated in the right-hand detail of  FIG. 5B , in which the features of the plug are identical to the features illustrated in the left-hand detail). The electrical contacts  504 ,  506  are electrically connected to a power supply (not shown), and the contact connection enables power to be transferred to the side contacts  501  and  502 . When the plug is not inserted in the socket the power circuit is completely isolated. 
       FIG. 6  shows one embodiment of a shroud to protect exposed conductors on a plug  602  when it is not inserted into a mating socket  603 . The contacts (not shown) are shrouded when the plug is floating (i.e. not in a socket). The action of insertion of the plug  602  into the socket  603  causes the shroud  601  to be pushed back over plug  602  to reveal the contacts. Upon removal of the plug  602 , resilient, sprung or other return means ensure that the shroud is displaced to its closed position, thereby isolating any earth paths. 
       FIG. 7  shows an embodiment of a power circuit isolator on a socket  707 . The contacts  701  and  702  are isolated by contacts  703 ,  704 ,  705  and  706  from the power available to the socket  707 . The action of insertion of the plug  708  into socket  707  enables the connection of contacts  703 ,  704 ,  705  and  706  thus putting power onto contacts  701  and  702 . 
       FIG. 8  shows an alternative embodiment of lateral power circuit contacts of reduced length in socket and shrouded by plug moulding. In this embodiment, the power may be present on either the contacts  801  and  802  in the plug  803  or on the reduced length contacts  804  and  805  in the socket  806 . 
       FIG. 9  shows an embodiment having an optical lens option for lower loss. For maximum optical power transfer, a lens  901  can be included in the plug  902  and/or socket  903 . 
       FIG. 10  shows an embodiment having an optical lens with a location for refractive index matching material. For maximum optical power transfer, refractive index matching material  1001  can be included in the plug  1002  and/or socket  1003 . 
       FIG. 11  shows in detail of one embodiment of a retainer for an optical fibre to ensure positive pressure between light transmission elements in the plug and socket. To overcome tolerances in the plug and socket assembly, the optical fibre  1101  is held slightly proud by retainer  1102  so that when the plug  1103  is fully mated with the socket  1104  the optical fibre exerts a positive pressure on the optical receiver or transmitter  1105 . 
       FIG. 12  shows a combined fibre and conductor option. In this embodiment, the fibre  1201  is encased in a metallic sheath  1202 . Metallic sheath  1202  can perform the dual function of securing and straightening the optical fibre as well as providing an electrical current path for the power or data. 
       FIG. 13  shows an alternative fibre arrangement to avoid crossover issues. By positioning the optical fibres  1301 ,  1302  about the central axis of the plug or socket, issues relating to crossover can be resolved. 
       FIG. 14  shows a plug with an optional pip or raised portion to achieve keying and thereby ensure against inadvertent insertion into a non compatible socket. One example of altering the dimensions and shape of the plug and socket from the standard 8P8C connector is so that the proposed plug do not fit a standard 8P8C socket; and also a standard 8P8C plug does not fit the socket according to the invention. Increased height of body of the plug will not fit into existing 8P8C socket. Decreased pip width of the socket will not allow access to wider pip of standard 8P8C plug. 
       FIG. 15  shows a plug option with master keying function. By amending certain features of the keying it is possible to produce a master plug that fits in a standard 8P8C socket and a modified socket. Likewise it is possible to produce a master socket that accepts both a standard 8P8C plug and a modified plug. 
     Although in the examples shown there are three or four connectors, the invention is not limited to this, for example an extra pair of optical fibre connectors can be provided. The limitations on how many connectors or data pins is a function of the size of the plug and socket, whether there is a requirement to match a standard plug-in connector unit and the cost that a purchaser finds acceptable. 
     Plug-in connectors according to the invention can provide one or more of the following: optic fibre connection which can be glass or plastic depending on requirements; a power supply; a typical 8 way cat 5 connection; power over Ethernet, programming input; extra data pins; and USB type application with higher voltage capability. 
     The invention is particularly well suited for the control of systems, such as for example household appliances, lights and devices, as the power (eg in pins  1  and  10  or the lateral faces) can be modulated, for example by way of amplitude modulation and/or frequency modulation, so as to control such devices simply and cheaply. This aspect also consumes very little power as the bandwidth is low. 
     The invention has been described by way of illustrative examples only and it will be appreciated that variation to the embodiments described may be made without departing from the scope of the invention as defend in the claims.