Abstract:
A network communications system is provided for allowing a group of computer users in a conference room or similar small work environment to access an Ethernet local area network (LAN) and to provide peer-to-peer group networking without connection to a backbone network. 
     The system includes multiple (for example, 4 or 8) client computer ports each including a removable spring loaded cable dispenser carrying an extendible/retractable Category 5 LAN cable terminated with an RJ-45 plug for connection to a client computer&#39;s network adapter. Combined power/Ethernet LAN cables connect the system to an enterprise network and to a source of electrical power, and permit cascading of up to three 8-port systems. 
     In use, a computer user pulls out the cable from one of the client ports and inserts the RJ-45 plug into the RJ-45 jack on the network adapter carried by the computer. After completion of the networking session, the user unplugs the cable which is automatically retracted by the spring loaded cable reel. A cable management system is thereby provided which eliminates the tangle or clutter of multiple cables encountered in existing systems.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This divisional application claims the benefit of U.S. patent application Ser. No. 09/534,888 for Network Communications System, filed Mar. 24, 2000 now U.S. Pat. No. 6,780,047, Assignee Intel Corporation. 

   FIELD OF THE INVENTION 
   The present invention relates generally to data communications networking and particularly to a network communications system allowing a group of computer users in a conference room or similar small work area to access a local area network (LAN) and to provide peer-to-peer group networking and resource sharing without accessing the LAN. 
   BACKGROUND OF THE INVENTION 
   The widespread use of notebook and handheld computer systems in business environments has created a need for informal network access and information sharing. Mobile users require constant access to the company network for E-mail, internet and intranet services. Small workgroups of mobile notebook and handheld computer users often assemble for a meeting or a joint task, access and exchange computerized information in an ad hoc manner and then disband. There is a need to facilitate this rapid workgroup “setup and tear down” in a conference room or similar small work area allowing two or more computer users to access a network at the same time, and also to share files, peripherals, and other resources without connection to a backbone network. 
   The availability of networking connections in conference rooms has heretofore been limited because of the high cost of custom conference room furniture with integrated LAN jacks. Thus, conference rooms are often equipped with only one LAN wall jack thereby limiting network access to only one user at a time. In addition, existing LAN hubs and switches are not designed to be seamlessly integrated into a conference room or similar environment. Thus, placing such a LAN interconnection apparatus in a conference room requires many individual network cables to connect users&#39; computers to the apparatus. Conference rooms so equipped are often plagued with a tangle of unsightly cables and sometimes cables are removed from the room. Moreover, mobile computer users moving about company premises to attend team meetings, view presentations or work on group projects must often carry their own network cables and search for open network jacks in a conference room or other work area. 
   SUMMARY OF THE INVENTION 
   Broadly, the present invention provides a network communications system for efficiently connecting a plurality of computer systems with a local area network in a small work area environment such as a conference room. The system includes a plurality of retractable cables connectable to a corresponding number of computers that eliminate the inevitable tangle of network cables that occur with existing hub and switch products. Further, the system facilitates the inexpensive addition of network connectivity to a conference room environment. 
   In accordance with one specific embodiment of the invention, there is provided a network communications system for networking a plurality of computers, the system including a plurality of client computer ports, multiport circuitry such as a LAN switch for interconnecting the plurality of client computer ports in the network, and a removable, replaceable, network communications cable dispensing device, preferably in the form of a spring loaded reel take-up device, associated with each client port. The communications cable carried by each cable dispensing device has a first portion and a second portion. The first portion of the communications cable is fixed relative to the cable dispensing device and has an extremity carrying a first connector adapted to be coupled to one of the ports of the multiport interconnecting circuitry. The second portion of the communications cable is extendible from and retractable, under spring load, into the cable dispensing device and has an extremity carrying a second connector adapted to be coupled to one of the computers. In accordance with a preferred embodiment, the communications cable comprises flat, Category 5 compliant LAN cable including two twisted wire pairs, and the connector at the extremity of each of the first and second portions of the communications cable comprises an RJ-45 modular plug. 
   Further in accordance with a preferred embodiment, the system includes a combined power/Ethernet LAN cable for connecting the system both to a network and to a source of electrical power. In addition, the system may include a combined power/Ethernet LAN cable for coupling the system to a second network communications system of the invention in cascaded or daisy chain fashion. 
   In accordance with another aspect of the present invention, the combined power/Ethernet LAN cable comprises a first group of conductors comprising two twisted wire pairs for transmitting Ethernet LAN signals. The first group of conductors has a first end and a second end, the first end being adapted to be connected to the Ethernet LAN. The combined cable further includes a second group of conductors comprising, like the first group of conductors, two twisted wire pairs for transmitting electrical power to the system. The second group of conductors has a first end and a second end, the first end of the second group of conductors being adapted to be connected to a source of electrical power. An RJ-45 modular connector having at least eight contact positions terminates the second ends of the first and second groups of conductors. The conductors of the fist group of conductors are connected to the contacts of a first group of four of the contact positions of the RJ-45 connector and the conductors of the second group of conductors are connected to the contacts of a second group of four of the contact positions of the RJ-45 connector. EMI/RFI shielding encloses the first group of conductors and an insulative jacket encloses both the first and second groups of conductors. In accordance with a specific embodiment of this aspect of the invention, the RJ-45 connector has ten contact positions, Nos. 1-10, the conductors of the first group of conductors being connected to the contacts of contact positions 1-4 and the conductors of the second group of conductors being connected to contact positions 7-10. The middle contact positions 5 and 6 of the RJ-45 connector are devoid of contacts to provide electrical isolation between the first and second groups of conductors. 
   In accordance with yet another aspect of the present invention, there is provided a power/Ethernet LAN adapter assembly comprising an enclosure having attached thereto a combined power/Ethernet LAN cable as described above; an electrical power cord; and a Category 5 compliant cable terminated with an RJ-45 modular plug for connection to a LAN. The enclosure contains pass-through conductors interconnecting the Category 5 compliant cable with the first end of the first group of conductors of the combined power/Ethernet cable, and a power supply interconnecting the power cord and the first end of the second group of conductors of the combined cable. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects, features and advantages of the invention will become evident from the detailed description, below, when read in conjunction with the accompanying drawings in which: 
       FIG. 1  is a schematic representation of a pair of 8-port network communications systems in accordance with a first embodiment of the invention, with the systems shown placed on a conference room table; 
       FIG. 2  is a top perspective view of one of the systems shown in  FIG. 1 ; 
       FIG. 3  is a bottom perspective view of the system shown in  FIG. 2 ; 
       FIG. 4  is a top perspective view of the system of the invention with the housing cover removed; 
       FIG. 5  is a top plan view of the system shown in  FIG. 4 ; 
       FIG. 6  is a perspective view of a LAN communications cable take-up device used in connection with the present invention; 
       FIG. 7  is a top plan view of the cable take-up device of  FIG. 6 ; 
       FIG. 8  is a top plan view of the system as seen in  FIG. 5  with the inner housing cover removed, exposing the printed circuit board (PCB); 
       FIG. 9  is a perspective view of the PCB; 
       FIG. 10  is a block diagram of the electronic circuitry of the first embodiment of the system; 
       FIG. 11  is a perspective view of the interior of the housing cover; 
       FIG. 12  is a simplified, transverse cross section of a portion of the PCB and housing cover, as seen along the line  12 — 12  in  FIG. 1 ; 
       FIG. 13  is a top plan view of an adapter assembly including a combined power/LAN cable, for connecting a network communications system of the invention with a source of electrical power and an enterprise Ethernet LAN; 
       FIG. 14  is a top plan view of a combined power/LAN cable for cascading network communications systems of the present invention; 
       FIG. 15  is a cross section view of the combined power/LAN cables of  FIGS. 13 and 14  as seen along the lines  15 — 15  therein; 
       FIG. 16  is a chart showing the contact assignments of the combined power/LAN cables of  FIGS. 13 and 14 ; and 
       FIG. 17  is a perspective view of a 4-port network communications system in accordance with a second embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   By way of example, the invention will be described with reference to the widely used 10/100 Mbps Ethernet local area networks (LANs) typically found in workplace environments. Such Ethernet LANs conform to the IEEE 802.3, 802.3u and 802.3x network standards which are incorporated herein by reference. 
   Referring first to the schematic representation of  FIG. 1 , there is shown a network communications system  10  for connecting, for example, a plurality of portable computers  12 ,  14  and  16  to each other and to an Ethernet local area network  18  via an RJ-45 wall jack  20 . The specific embodiment of the system  10  shown in  FIG. 1  has eight (8) client or computer ports  22  for connecting as many computers. 
   The computers  12 ,  14  and  16  typically comprise notebook or handheld computers provided with network interface cards or adapters  24 . Examples of such adapters  24  are the Ethernet PC Cards and Ethernet/Modem Combo PC Cards manufactured by Xircom, Inc., Thousand Oaks, Calif. A flat, Category 5 compliant LAN cable  26  terminated with an RJ-45 modular plug  28  connects-each of the computers  12 ,  14  and  16  with the system  10 . The system  10  is a compact unit designed to be placed on a conference room table top  30  a portion of which is shown in  FIG. 1. A  default mode for the operation of the system  10  might be client-to-enterprise LAN access. The network communications system  10  may also operate as a stand alone client concentrator facilitating networking among the users within a conference room with or without connection to a backbone network. 
   The network communications system  10  is connectable to a standard electrical power wall outlet  32  and to the Ethernet LAN  18  by means of an adapter assembly  34 . The adapter assembly  34  includes a power cord  36  for connection to the wall outlet  32 ; an Ethernet LAN cable  38  terminated with an RJ-45 modular plug  40  for connection to the LAN wall jack  20 , and a combined power/Ethernet LAN cable  42  described in greater detail below. In addition, in accordance with a preferred embodiment of the invention, the system  10  may be coupled to a second, cascaded network communications system  44 . Up to three (3) 8-port systems may be cascaded or daisy chained in this fashion thereby facilitating the networking of up to twenty-four (24) computers. Such cascading is effected by means of combined power/Ethernet LAN daisy chain cables  46  and  48 , also described in greater detail below. 
   With reference now also to  FIGS. 2-5 , the system  10  comprises an outer housing  50  including a base  52  and a cover  54 , each preferably fabricated of molded plastic. The base  52  of the outer housing  50  includes a bottom wall  56  having inner and-outer surfaces  58  and  60 , and opposite side walls  62  and  64  defining the eight (8) client computer ports  22  from each of which a flat LAN cable  26  may be pulled out by a user for connection to a computer. Four rubber feet  66  attached to bottom wall  56  adjacent the corners thereof help resist any tendency for the system  10  to slide along the table top  30  when a cable is withdrawn from a client port  22 . The four client ports  22  along one side  62  of the base  52  are in transverse alignment with the four client ports  22  along the other side  64  of the base  52 , as best seen in FIG.  5 . The cover  54  has a generally horizontal top wall  68  having an inner surface  70  and an outer surface  72 . 
   The inner surface  58  of the bottom wall  56  of the base  52  defines eight (8) wells  80  each of which is positioned adjacent one of the client ports  22 . With reference now also to  FIGS. 6 and 7 , removably mounted within each of the wells  80  is a generally cylindrical communications cable dispenser  82 . The dispensers  82  are identical; each preferably takes the form of a take-up device containing a spring loaded reel carrying communications cable  84 . A cable dispenser or take-up device of the type that may be used with the present invention is generally disclosed in U.S. Pat. Nos. 5,797,558 and 5,655,726, which patents are incorporated herein by reference. As already indicated, in the preferred embodiment under consideration, the communications cable  84  carried by the reel of each cable dispenser  82  is in the form of flat, Category 5 twisted pair 10/100 Mbps Ethernet transceiver cable: Each cable dispenser  82  has a casing  86  including two projections  88  and  90  on the outer surface thereof. The projection  88  has a transverse surface  92  -and the projection  90  has a transverse surface  94 . The cable  84  of each cable dispenser  82  has a first portion  96  that emerges from an aperture in the transverse surface  92  of the projection  88 . The first portion  96  of the cable  84  is fixed, that is, it is non-extendible relative to the cable dispenser  82 . The cable  84  includes as a second portion the cable length  26  that is extendible from an aperture in the transverse surface  94  of the projection  90  against a resilient bias provided, for example, by a flat coil spring within the dispenser  82 , and is thereby retractable into the dispenser. Further, in the present invention, the cable dispenser preferably includes a mechanism for allowing the cable to be latched in an extended state to relieve strain on the cable during use. A mechanical switch  100  in the top surface  101  of the cable dispenser casing  86  allows a user to select latching or non-latching reel operation. The length of the second portion  26  of the cable  84  is compatible with typical conference room environments, for example, six to eight feet long, The first and second portions  96  and  26  of the cable  84  have ends  102  and  104 , respectively, carrying an RJ-45 modular plug  106  and the RJ-45 modular plug  28 . The plug  28  has a rear surface  110  provided with a slotted, resilient pad  112  that engages the transverse surface  94  of the projection  90  on the casing  86  to absorb shock in the event a user suddenly releases the extended cable portion  26 . Mounted on the top surface  101  of the dispenser casing  86  and extending along a diameter thereof, is an upwardly projecting, flat grip or handle  114  facilitating the lifting of the cable dispenser  82  and the removal thereof from its associated well  80 . Adjacent the inner end  116  of the handle  114  and disposed perpendicular thereto is a short, upstanding abutment  118 . 
   The base  52  of the system  10  includes a molded plastic inner housing  130  extending the length of the base. The inner housing  130  has a horizontal upper wall  132  that defines eight (8) longitudinally spaced jack apertures  134  and four transverse channels  136 , each channel being in alignment with a pair of opposed client ports  22 . The inner housing  130  further includes a generally vertical wall  138  defining eight (8) arcuate recesses  140  for receiving the inner portions of the cable dispensers  82 . A portion of the vertical wall  138  in each arcuate recess  140  is slotted (at  142 ) so as to define a generally U-shaped, resilient tab  144  hinged along the bottom thereof. The resilient tab  144  carries an outwardly projecting latch  146  that engages the top of the abutment  118  on the top of the associated cable dispenser  82  to lock the dispenser in place and prevent it from being lifted. To remove a cable dispenser  82  for replacement, the associated resilient tab  144  is pressed inwardly, that is, away from the dispenser, thereby causing the latch  146  to clear the associated abutment  118  thus allowing the dispenser to be lifted out of its well  80  by means of the handle  114 . Projecting upwardly from the inner surface  58  of the bottom base wall  56  is a stop  148  that engages the transverse surface  94  on the dispenser projection  90 . The stop  148  thereby prevents the cable dispenser  82  from rotating counterclockwise within its well  80  when the second portion  26  of the cable  84  is withdrawn from the dispenser. 
     FIG. 8  is a top plan view of the base of the communications system with the inner housing  130  removed thereby exposing a printed circuit board (PCB)  150  extending substantially the length of the base  52 .  FIG. 9  is a perspective of the PCB  150 . Mounted on one surface of the PCB  150  are first and second monolithic integrated circuits  152  and  154  comprising network interconnection circuitry preferably in the form of LAN switches. Mounted on the other surface of the PCB  150  opposite the LAN switch IC&#39;s  152  and  154  are heat sinks  156  and  158 , respectively, for transferring heat away from the switches. The PCB  150  also carries an inverted 10-contact RJ-45 jack  160  at one end of the PCB  150  for connection to the combined power/Ethemet LAN cable  42  of the adapter assembly  34 , and an inverted 10-contact RJ-45 jack  162  at the other end of the PCB  150  for connecting the system  10  to the second communications system  44  by means of the combined power/Ethernet LAN daisy chain cable  46 . The PCB  150  further carries eight (8) upright client port RJ-45 jacks  164  intermediate the ends of the PCB. The jacks  164  are arranged as two pairs  164   a ,  164   b  of individual jacks and a central jack complex  164   c  integrating the remaining four RJ-45 jacks  164  in a single unit. With the inner housing  130  in place in the base  52 , the eight client port jacks  164  carried by the PCB line up with the jack apertures  134  in the upper wall  132  of the inner housing  130 . 
     FIG. 10  is a high-level block diagram of the electronics of the 8-port network communications system  10 . As shown in  FIG. 10 , the first switch  152  may comprise, by way of example, a Model BCM5308 single chip, 3.3 volt 10/100 BASE-T/TX 9-port switch manufactured by Broadcom Corp. The second switch  154  may comprise a Model BCM5304 single chip, 3.3 volt 10/100 BASE-T/TX 5-port switch also manufactured by Broadcom Corp. The switches  152  and  154  are connected by an expansion bus  168  and are coupled to SRAM buffer memories  170  and  172 , respectively. Six transmit/receive ports of the first switch  152  interface with the enterprise power/Ethernet RJ-45 jack  160  and five of the client port RJ-45 jacks  164  which receive the mating RJ-45 plugs  106  on the ends  102  of the fixed cable portions  96 . Three transmit/receive ports of the second switch  154  interface with the RJ-45 jacks  164  of the remaining three client ports. A fourth transmit/receive port of the second switch  154  interfaces with the cascade or daisy chain RJ-45 jack  162 . A pass-through 24vdc power bus  174  for supplying cascaded systems such as the system  44  is connected between the power/Ethernet and daisy chain jacks  160  and  162 . Connected to the 24vdc bus  174  is a regulator  176  for supplying 3.3vdc to the various IC&#39;s carried by the PCB  150 . 
   The use of multiport network interconnecting circuits such as the LAN switches  152  and  154  and their connection to LAN port jacks are well known in the art and need not be described in greater detail. It will also be obvious to those skilled in the art that instead of a LAN switching arrangement, the system may be set up as a less expensive, conventional concentrator or repeater hub. 
   The system  10  also includes means for providing a visual indication of the status of each of the client ports  22 . With reference to  FIGS. 4 and 5 , with the inner housing  130  in place, four portions  178  of the PCB  150  are exposed by the transverse channels  136  defined by the inner housing. With reference also to  FIGS. 8 ,  9  and  12 , each of the exposed portions  178  of the PCB carry a set of three status indicating LEDs  180 - 182  on each side of the PCB, each set of LEDs being associated with one of the client ports  22 . The LEDs of each set are vertically aligned with the upper two LEDs  180  and  181  in close proximity to each other and the third LED  182  being below and spaced apart from the upper pair. The upper pair of LEDs  180 ,  181  of each LED set indicates (through 2 different colors) link integrity, that is, whether a good 10 Mbps or 100 Mbps connection has been made, while the third LED  182  of each set indicates LAN send/receive activity. Light from-the LEDs is transmitted to the exterior surface  72  of the cover  54  via light pipes of Lexan or the like. Specifically, as shown in  FIGS. 11 and 12 , each client port has associated with it a pair of vertically aligned, upper and lower, L-shaped light pipes  184  and  186  carried by the inner surface  70  of the cover  54 . The light pipe  184  has an inner end  184   a  and an outer end  184   b . Likewise, the light pipe  186  has inner and outer ends  186   a  and  186   b . With the outer housing cover  54  in place, the inner end  184   a  of the upper light pipe  184  is positioned to receive light from one or the other of the LEDs  180 ,  181  of the upper LED pair; similarly, the inner end  186   a  of the lower light pipe  186  is positioned to receive light from the lower LED  182  when the cover  54  is in place. The outer ends  184   b  and  186   b  of the light pipes  184  and  186  communicate with the outer surface  72  of the cover  54  and thus light transmitted by the light pipes from the LEDs is visible to the users of the system to indicate the status of each client port  22 . The use of LEDs to indicate the status of LAN ports is well known in the art, being routinely used, by way of example, in connection with network interface cards or adapters such as those mentioned above. 
     FIG. 13  shows the details of the adapter assembly  34  for connecting the system  10  to the enterprise LAN  18  and the source of electrical power  32 . The adapter assembly  34  comprises an enclosure  190 , the combined power/Ethernet LAN cable  42  extending from one end of the enclosure  190 , and the 120vac power cord  36  and Category 5 compliant Ethernet LAN cable  38  extending from the other end of the enclosure  190 . With reference also to  FIGS. 3 and 10 , the combined power/Ethernet LAN cable  42  has first and second ends  42   a  and  42   b  and is terminated at the end  42   b  with a 10-contact position RJ-45 modular plug  192  for connection to the internal jack  160 , while, as already indicated, the LAN cable  38  is terminated with an eight contact RJ-45 modular plug  40  for connection to the wall LAN jack  20 . The enclosure  190  contains a PCB  194  carrying a 120vac-to-24vdc power supply  196  connected to the power cord  36  and conductors  198  providing a pass-through for the Ethernet LAN signals. By way of example, the overall length of the adapter assembly of  FIG. 13  may be 25 feet. 
   As shown in the cross section of  FIG. 15 , the combined power/Ethernet cable  42  includes a core group of Category 5 compliant conductors comprising two twisted wire pairs  200 / 201  and  202 / 203  connected to the pass-through conductors  198  for transmitting network signals. The core group of conductors  200 - 203  is encased in insulative filler material (for example, fibrillated polypropylene)  204  in turn enveloped by a tubular, double sided aluminum foil/mylar EMI/RFI shield  206  having a drain line  208 . The shielding  206  is surrounded by fibrillated polypropylene filler  210  which in turn is enveloped by a braided EMI RFI shield  212  and an outer tubular. insulative jacket  214  of, for example, flexible PVC. Embedded in the filler  210  is an outer group of conductors comprising two twisted wire pairs  216 / 217  and  218 / 219  connected to the power supply.  196  for supplying 24vdc electrical power to the system  10 . 
   With reference to  FIG. 14 , the combined power/LAN cable  46  for cascading the systems  10  and  44  is identical to the combined power/LAN cable  42  of the adapter assembly  34  except that the cascading cable  46  is terminated at each of the first and second ends  46   a  and  46   b  with a 10-contact RJ-45 modular plug  220 . With reference also to  FIGS. 3 and 10 , to cascade the systems of the invention, one of the plugs  220  is inserted in the daisy chain RJ-45 jack  162  of the first system such as the system  10  while the other plug  220  is inserted in the enterprise RJ-45 jack  160  of the second system such as the system  44 . The overall length of the cable  46  may be 6 feet, for example. 
     FIG. 16  is a chart listing the pin or contact assignments of the mating 10-contact RJ-45 modular plugs and jacks used in the system of the present invention. Thus, the conductors  200 / 201  and  202 / 203  of the core or LAN group of conductors are connected to contact Nos. 1-4 while the conductors  216 / 217  and  218 / 219  of the outer or power group of conductors are connected to contact Nos. 7-10. Middle contact positions Nos. 5 and 6 are devoid of contacts so as to provide additional electrical isolation between the two groups of conductors. 
   With reference again to  FIGS. 3-5  and  8 , in the event heat dissipation from the LAN switch ICs  152  and  154  through the use of heat sinks  156 ,  158  alone is insufficient, a cooling fan  230  housed within a slotted enclosure  232  at one end of the system  10  may be provided. Cooling air discharge slots  234  formed in the bottom wall  56  of the base  52  at the other end of the system  10  vent cooling air flowing along the length of the PCB  150 . 
   With reference to  FIG. 17 , there is shown an alternative embodiment of the invention comprising a system  240  having four client computer ports  242  two of which are visible in FIG.  17 . It will be evident that the preceding detailed description applies equally to the four port version of the invention, except that typically only a single LAN switching IC would be required. 
   While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and detail may, be made therein without departing from the scope of the invention as defined by the appended claims. For example, it will be appreciated by those skilled in the art that the invention is equally applicable to “small office/home office” (SOHO) environments.