Abstract:
Apparatus for use with a cable for interconnecting electronic devices is described. The apparatus includes an indicator for identifying a characteristic of the cable, and includes a mechanism operable to cause the indicator to identify the characteristic of the cable. The indicator can be for example an LED and can be used to identify the location of an end of the cable. The mechanism can be a pushbutton located at the other end of the cable. The LED is illuminated when the pushbutton is activated. A signal generator is responsive to the pushbutton and provides a signal to the LED to cause the LED to illuminate. The signal generator can be implemented with a DMTF encoder.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to cables for interconnecting electronic devices, and more particularly to mechanisms for identifying characteristics of such cables. 
     BACKGROUND OF THE INVENTION 
     Many of today&#39;s corporations have large data network infrastructures. A typical office building data closet has a patch-panel containing many connectors for network cables that run to the offices and cubicles elsewhere in the building. Network equipment often sits in a nearby rack. Network cables connect each of the office ports to one of the ports on the network equipment through the patch-panel. As users move, or network equipment is upgraded or replaced, the cables tend to become entangled. It becomes very difficult to identify the locations of cable ends. For instance, when a cable is plugged into a port on the network equipment, it is difficult to determine where on the patch panel the other end of the cable resides. In order to determine which network port is connected to a particular office cable-drop (or vice versa), most technicians today use one of two techniques. The first is to unplug the cable from the patch panel, and see whether any of the link-status lights on the network equipment goes out. If one does, the technician knows which port he has just disconnected. If not, it means the equipment in the user&#39;s office is not connected or not powered up. When successful, this first technique disadvantageously causes the momentary disruption of network connectivity. When unsuccessful, the technician must then use the second technique, which involves tugging the cable, running one&#39;s hands along it, and so forth to attempt to trace the cable manually. The problem is exacerbated when many cables run through a constricted opening, or are tightly bound together with a cable-strap. It would be desirable to provide a network cabling system which overcomes the above-described inadequacies and shortcomings. 
     SUMMARY OF THE INVENTION 
     In accordance with the principles of the invention, there is provided apparatus for use with a cable for interconnecting electronic devices. The apparatus includes an indicator associated with a cable for identifying a characteristic of the cable, and includes a mechanism operable to cause the indicator to identify the characteristic of the cable. The characteristic identified can be the location of one end of the cable. According to an aspect of the invention, the indicator is an LED located on one end of the cable. The mechanism is a pushbutton located at the other end of the cable. The LED is illuminated when the pushbutton is activated. A signal generator is responsive to the pushbutton and provides a signal to the LED to cause the LED to illuminate. The signal generator may conveniently be implemented as a DTMF encoder. 
     The apparatus may further include a power detector circuit responsive to the pushbutton for detecting whether power is available on the cable. The power detector circuit causes power to be provided to the cable if power is not already available on the cable. An embodiment of the cable is for interconnecting Ethernet devices which are IEEE 802.3af compatible. 
     According to an alternate aspect of the invention, the mechanism operable to cause the indicator to identify the characteristic of the cable may be a magnetically coupled device. According to another aspect of the invention, the indicator may be a sound generator. 
     Also according to the principles of the invention, a cable system is provided for interconnecting electronic devices. A first cable is provided for connecting to a first electronic device. The first cable includes an indicator, such as an LED, for identifying a characteristic of the first cable that plugs into the electronic device. A second cable is provided for connecting to a second electronic device. The second cable includes a mechanism, such as a pushbutton, operable to cause the indicator to identify the characteristic of the first cable. The characteristic may be the location of the end of the first cable that is connected to the first electronic device, and the indicator may be an LED located on the end of the first cable. 
     Further in accordance with the principles of the invention, apparatus for interconnecting electronic devices includes a first electronic device, a second electronic device, and a cable for transferring power and information between the first electronic device and the second electronic device. An indicator for identifying a characteristic associated with one end of the cable is provided. A mechanism is operable to cause the indicator to indicate the characteristic associated with the one end of the cable by causing a signal to be transferred to the indicator via the cable. The indicator may be located on the first electronic device while the mechanism comprises a pushbutton located on the second electronic device. Alternately, the mechanism may be a circuit located in the second electronic device, the circuit being responsive to user commands to cause a signal generator to produce the signal. 
     All of the variations of the invention herein described are advantageous to locate cable ends without disrupting network connectivity or causing undue manual searching. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to facilitate a fuller understanding of the present invention, reference is now made to the appended drawings. These drawings should not be construed as limiting the present invention, but are intended to be exemplary only. 
         FIG. 1  is a schematic view of an office environment in which various network devices are interconnected to network equipment via cables. 
         FIG. 2  is a perspective view of a cable according to the principles of the invention. 
         FIG. 3  is a schematic view of the components of the cable of  FIG. 2 . 
         FIG. 4  is a flow diagram of the operation of the power detection circuit of  FIG. 3 . 
         FIG. 5  is a perspective view of a cable according to another embodiment of the invention. 
         FIG. 6  is a schematic view of the components of the cable of  FIG. 5 . 
         FIG. 7  is a schematic view of a cable system for interconnecting a network device and network equipment. 
         FIG. 8  is a perspective view of a cable according to another embodiment of the invention. 
         FIG. 9  is a perspective view of a cable according to another embodiment of the invention. 
         FIG. 10  is a schematic view of a cable system where the signal generator is resident within the network equipment. 
         FIG. 11  is a schematic view showing the arrangement of the components of the cable system of  FIG. 10 . 
         FIGS. 12A and 12B  are schematic views of other embodiments of the cable system of  FIG. 10 ; 
         FIG. 13  is a schematic view of another embodiment of the cable system of  FIG. 10 . 
         FIG. 14  is a schematic view of a cable system where the signal generator is resident within the network equipment and the signal decoder is resident within the patch panel. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In  FIG. 1  there is shown a typical office environment wherein network devices  10  in offices or cubicles  12  are connected by cables  14  to a patch panel  16  located in a wiring closet  18 . The wiring closet  18  also includes racks of network equipment  20 . The ports  22  on the network equipment  20  are connected via cables  24  to ports  26  on the patch panel  16 , thereby establishing network connectivity between the network equipment  20  and the network devices  10 . The network devices  10  may be for example computer network adapters, IP telephones, and the like. The network equipment  20  may be for example routers, Ethernet switches, and the like. A given wiring closet  18  may contain patch panels  16  and network equipment  20  having hundreds of ports, thus requiring hundreds of cables  24 . 
     The network equipment  20  and network devices  10  are preferably Ethernet devices that conform to the IEEE 802.3af standard, currently described in IEEE Draft 802.3af/D3.0, herein incorporated by reference, which specifies a technique for providing power to the Ethernet cable in order to power Ethernet 802.3af compliant devices. This standard uses a detection signature to determine whether a network device  10  that requires power is plugged into the network. If so, the network equipment  20  provides 48 V power to the network device  10  over the cables  24  and  14 . In accordance with the standard, a network device  10  that is capable of receiving power from network equipment  20  via the signal lines provided through the cable  24  presents the detection signature to the network equipment  20  so that the network equipment  20  can determine that the network device  10  is capable of receiving power over the cable  24 . In particular, the network device  10  that is capable of receiving power over the cable  24  provides a signature characterized by a DC resistance of between 25,000 Ohms +/−5%, and a capacitance of less than 0.1 uF capacitance. The network equipment  20  contains a detection circuit that produces a detection voltage between 2.8 and 10 volts when connected to a network device  10  that presents the proper detection signature. The detection measurements reject resistances below 15,000 Ohms and above 33,000 Ohms. If slope comparisons detect a resistance of about 25,000 ohms, power will be provided to the network device  10  via either signal pairs  1 , 2  and  3 , 6 , or signal pairs  4 , 5  and  7 , 8  on the standard RJ45 twisted pair Ethernet cable. 
     In  FIG. 2  there is shown an embodiment of a cable  24  in accordance with the principles of the invention. The cable  24  includes an indicator  28  at one end for connection to a port  22  on the network equipment  20 . The indicator is herein shown to be an LED. The cable  24  includes a mechanism  30  at the other end of the cable located at the patch panel, which when activated, causes the LED to illuminate. The mechanism  30  is herein shown to be a pushbutton. A person can thereby push the pushbutton  30  at the patch panel end of the cable  24  to determine the location of the other end of the cable  24 , or determine the port  22  on the network equipment  20  into which the other end of the cable  24  is connected. 
     Referring to  FIGS. 2 and 3 , the pushbutton  30  activates a power detector circuit  32  within the end  34  of the cable  24 . The power detector circuit  32  is coupled to a pair of signal lines carrying power within the cable, as specified by the 802.3af standard. The power detector circuit  32  is coupled to a signal generator  36  within the end  34  of the cable  24 . The signal generator  36  is coupled through the signal lines carrying power within the cable  24  to a signal detector  38  located in the end  40  of the cable  24 , which is in turn coupled to the LED  28 . 
     According to one embodiment of the power detector circuit  32  as shown in  FIG. 4 , when the pushbutton is activated (step  42 ), the circuit  32  determines whether there is power on the cable (step  44 ). If the cable is plugged into an 802.3af compliant network device  10 , power will be present and can be applied to the signal generator  36  (step  46 ). If no power is present, then either the network device  10  is not 802.3af compliant, or the network device  10  is turned off, or the cable  24  is not plugged in. The power detector circuit  32  is 802.3af compliant and can apply a 25,000 Ohm powered-device detection resistor as described above, thus causing power to be applied from the network equipment  20  to the cable  24  if no power is otherwise present (step  48 ). 
     Activation of the pushbutton  30  causes power to be applied to the signal generator  36 . The signal generator  36  places a signal  50 , such as a low-frequency, low-amplitude alternating current potential, across one of the pairs of wires within the cable  24 , in accordance with any of a number of known techniques. This signal is received by the signal detector  38  coupled to the LED  28  at the other end  40  of the cable  24 , and causes the LED to illuminate in response to reception of the signal  50  in accordance with known techniques. 
     The signal generator  36  may generate the signal  50  only while the pushbutton  30  is activated, causing the LED  28  to illuminate only while the pushbutton  30  is activated. Alternately, the signal generator  36  may contain a delay element that causes power to be applied to the LED  28  for a certain minimum amount of time such that the LED  28  stays lit for a certain period of time after the pushbutton  30  is activated. According to another embodiment, the pushbutton  30  may activate a double throw switch such that power will be applied to the LED  28  upon a first activation of the pushbutton  30 , and will remain applied until a second activation of the pushbutton  30 . Such functionality is advantageous where the patch panel  16  and network equipment  20  are not within visual range of each other. A person can push the pushbutton  30 , leave to find the other end of the cable having the illuminated LED  28 , and return to disable the LED  28  by pushing the pushbutton  30  again. 
     According to a preferred embodiment of the invention, the signal generator  36  is a dual tone multi-frequency (DTMF) tone generator, of the sort known for generating touch tone signals in telephones. When the pushbutton  30  is activated, the DTMF tone generator  36  generates a tone, consisting of a pair of low frequency pulsed signals, on one of the cable wire pairs. The signal is coupled to the signal detector  38 , which causes the LED  28  to illuminate. The signal detector  38  may be a DTMF decoder, or may be a simpler circuit responsive to the tone. Employment of the DTMF tone generator  36  is advantageous in that different tones can be employed for different cables  24 , thus minimizing interference between close cables in the event that several close cables need to be activated at the same time. Employment of the DTMF tone generator  36  also allows a series of different tones to be supplied to the signal detector  38 , which can be used to cause the LED  28  to blink in selected patterns. Multiple LEDs of different colors could be employed, each color responsive to a particular DTMF tone. 
     Referring to  FIG. 5 , an alternate embodiment of the invention is shown, wherein the cable  24  includes a pushbutton  30  and an LED  28  at each end. In this embodiment, each end of the cable  24  includes the power detector circuit  32 , the signal generator  36 , and the signal detector  38  as shown in  FIG. 6 . This cable is advantageous in that the cable may be traced from either end, i.e. from the patch panel  16  to the network equipment  20  or vice versa. 
     In  FIG. 7  there is shown an embodiment of the invention employing multiple cables. A cable  52  located in an office or cubicle  12  includes a pushbutton  30 . The cable  52  connects a network device  10  to a wall receptacle  54  on a wall of the office  12 . Another cable  14  connects the wall receptacle  54  to a port  26  on the patch panel  16 . A cable  24  is connected between a port  26  on the patch panel  16  and a port  22  on the network equipment  20 . In this example, a person would like to locate the port  22  on the network equipment  20  to which the network equipment  10  is attached. The cable  52  includes the pushbutton  30 , power detector circuit  32 , and signal generator  36  as shown in  FIG. 3 . The pushbutton  30  on the cable  52 , when activated, causes the signal generator  36  to generate a signal that travels through the cables  52  and  14  to the patch panel  16  and onto the cable  24 . The cable  24  includes the signal detector  38  and LED  28  at the end of the cable  24  that is plugged into the network equipment  20 . The signal detector  38  receives the signal from the signal generator  36 , and thus causes the LED  28  at the end of the cable  24  to illuminate in response to the activation of the pushbutton  30  on the cable  52 . The network port  22  associated with the network device  10  located in the office or cubicle  12  can thereby be identified directly from the office or cubicle  12 . 
     It is also certainly possible to reverse the cable  52  such that the pushbutton is located at the wall receptacle  54 . It is also possible to implement the cable of  FIG. 2  or  5  for each of cables  14  and  24  so that the entire network segment can be traced. 
     In an environment where 802.3af compatible equipment is not available, a cable such as cable  24  could have a connector  56  mounted at one end of the cable that allows an external power source to cause the LED  28  at the other end of the cable to become illuminated. For example, as shown in  FIG. 8 , the LED  28  may be coupled to a cable wire pair at one end of the cable  24 , and a simple battery  58  may be clipped to the connector  56  at the other end of the cable  24  to cause the LED  28  to illuminate. 
     The mechanism  30  for causing the indicator, herein the LED  28 , to light may alternately be an external signal that is magnetically coupled directly into the cable  24 , allowing identification of one or both ends of the cable  24  by applying a device to the middle of the cable. For example, as shown in  FIG. 9 , a cable  24  contains an LED  28  at each end. Each end of the cable  24  contains a signal detector  38  as shown in  FIG. 3 . A magnetically coupled device  60  is attached to the middle of the cable  24 . The magnetically coupled device generates an alternating current signal  50  that couples to the cable wire pairs to which the circuit  38  is coupled, thereby causing the circuit  38  to illuminate the LEDs  28  at each end of the cable. 
     The indicator  28  can be implemented as a sound generator rather than an LED. This could be useful in very large environments where finding a blinking LED might be too time-consuming. 
     The activating signal  50  can also be generated by the network equipment  20  that is supplying the 802.3af compliant power. As shown in  FIG. 10 , a cable  24  is plugged into a port  22  on network equipment  20 . The signal generator  36  is located within the network equipment  20  and is coupled to the cable  24  through the port  22 . A pushbutton  30  located near the port  22  can be activated in order to cause the LED  28  at the other end of the cable  24  to illuminate. As shown in  FIG. 11 , the cable  24  includes a signal detector  38  for receiving the signal generated by the signal generator  36 . Also included in the cable is the power detector circuit  32  previously described, for determining whether power is available on the cable and for employing the power detection resistor in the cable if needed. The power detector circuit  32  causes power to be applied to the signal detector  38 . The power detector circuit  32  operates as shown in  FIG. 4  except that step  42  is not required. The power detector circuit  32  is not responsive to the pushbutton; rather, it ensures that power is always provided over the cable by the network equipment  20 . For example, to implement step  48 , the power detector circuit  32  can consist of a transistor circuit and a 25 K Ohm resistor. When the cable is plugged into an 802.3af compliant device, the transistor circuit ensures that the 25 K Ohm resistor remains out of circuit. When power is not present, the transistor circuit causes the 25 K Ohm resistor to be in circuit so that it can be sensed by the network equipment  20 . Alternately, the power detector circuit  32  can consist of a charge pump circuit that accumulates energy from the ramp pulses that the network equipment sends to check for an 802.3af compliant device, and can apply the accumulated energy to power the signal detector  38  and illuminate the LED  28 . Such a charge pump circuit is described in commonly owned co-pending patent application Ser. No. 09/696,279, filed Oct. 25, 2000. The signal generator  36  is powered by the network equipment  20  and provides power over the cable signal lines as defined in the 802.3af standard, along with the signals  50  for powering the LED  28 . 
     The power detector circuit  32  can be enhanced such that it “wakes up” on a periodic basis, checks for power, and places the 25 K Ohm resistor in circuit if needed. The signal detector  38  then causes the LED  28  to illuminate if a signal is being sent at that time by the signal generator  36 . 
     Further aspects of the invention are shown in  FIGS. 12A  where the signal generator  36  is located within the network equipment  20  and is implemented as a DTMF tone generator. In addition, in  FIG. 12B  the signal decoder  38  is implemented as a DTMF tone decoder in the cable  24 . The indicator  28  is a multi-digit LED display capable of displaying individual characters. The DTMF tone generator  36  generates multiple tones dependent upon the network equipment  20  port  22  location into which the cable  24  is plugged. Thus, activation of a pushbutton  30  near a port  22  on the network equipment  20  causes for example two tones to be generated—herein shown as the DTMF tones for “2” and “7”. The DTMF tone decoder  38  decodes these tones and causes the LED display to display “27”, the port on the network equipment  18  into which the cable is plugged. A person at the patch panel can now look at the cable and know which port on the network equipment it is plugged into. 
     Alternatively, as shown in  FIG. 13 , the signal generator  36  within the network equipment  20  may be activated via internal activation circuitry  62  rather than in response to the activation of a pushbutton  30 . Various user commands  64  can be generated, for example via SNMP commands, to cause various indications. The activation circuitry  62  can be responsive to a user command  64  in order to cause the signal generator  36  to provide tones that indicate a characteristic of the port into which the cable is plugged. For example, the signal generator  36  may provide a first tone if the port  22  is a high speed port, or a second tone if the port  22  is a low speed port. The different tones can be decoded by the signal decoder  38  to cause the LED  28  at the end of the cable to blink at different rates. For example, if the cable  24  is plugged into a high speed port, the LED  28  may be steadily illuminated. Alternatively, if the cable  24  is plugged into a low speed port, the LED  28  may blink. If the LED  28  is implemented as a digital LED display, as was shown in  FIG. 12 , certain numbers and/or letters can be displayed that would indicate the characteristic of the port into which the cable is plugged. A user command  64  “show port number” can be sent to the activation circuitry  62  which then causes the signal generator  36  to generate a series of tones that is decoded by the signal decoder  38  to cause the LED display  28  to display the port number. Another user command  64  “show port speed” can be sent to the activation circuitry  62  which then causes the signal generator  36  to generate a series of tones that is decoded by the signal decoder  38  to cause the LED display  28  to display an indication of the port speed. 
     In another embodiment, as shown in  FIG. 14 , the signal detector  38  may be located within the patch panel  16 , and the LED may be located on the patch panel  16  near a port  26 . The signal generator  36  located within the network equipment  20  generates a tone  50  that travels through the cable and is decoded by the signal decoder  38 , causing the LED on the patch panel  16  to illuminate. Again the LED can be a simple LED or an LED display, and activation circuitry  62  with the network equipment  20  can cause the signal generator  36  to generate tones representative of port characteristics, which can then be displayed by the LED or LED display on the patch panel  16 . In this embodiment, the patch panel  16  may be an 802.3af compatible device and may thus obtain power from the network equipment  20  to power the signal decoder for each port. Alternately, the cable may contain the previously described power detector circuit  32  and may then cause power to be provided from the network equipment  20  to the patch panel  16 . 
     According to other embodiments, the activation circuitry is not only responsive to user commands, but can also operate independently. The activation circuitry  62  may cause the signal generator  36  to send a signal that causes the port number to always be displayed. Or, the activation circuitry  62  may cause the signal generator  36  to send tones at fixed intervals, for example every 10 seconds, such that the cable periodically displays the port number into which it is plugged, or a characteristic of the port into which it is plugged, for example high speed port vs. low speed port. The circuitry  62  can also cause the signal generators  36  associated with each port on the network equipment  20  to “sound off”—that is, the signal generators  36  periodically send tones onto the cables  24 , causing each cable to periodically illuminate its LED or display its port number. Such functionality could also be provided on request via the user command. In all such embodiments, the indicator LED may be located either on the cable  24  itself or on the patch panel  16 . 
     Furthermore, referring back to  FIG. 7 , it can be seen that any of the embodiments of  FIGS. 10–14  may be employed in the multi-cable embodiment shown in  FIG. 7 . For example, the signal generator  36  located in the network equipment  20  can send tones through the multiple cables  24 ,  14 , and  52  of  FIG. 7  so that a person can view the LED or LED display  28  located on the cable  52  that is connected to a network device  10 . 
     The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the present invention, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such modifications are intended to fall within the scope of the following appended claims. Further, although the present invention has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present invention can be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present invention as disclosed herein.