Abstract:
A network documentation and revision system is presented that includes first and second devices connected by a patch cord. The first device has provisioning and signal ports with corresponding contact assemblies. The second device has a switch port without a contact assembly. The patch cord has signal and control wires, a first connector that connects the signal wires into a signal port and the control wire to a corresponding contact assembly, and a second connector that connects the signal wires to the switch port and terminates the control wire. The second connector contains an indicator controlled by control circuitry, detection circuitry detecting whether the second connector is plugged into the second device, and ID circuitry providing an ID number through the first connector. Installation or removal of the patch cord is guided by indicators on the patch cord and first device without retrofit contacts being added to the second device.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. application Ser. No. 11/560,112, filed Nov. 15, 2006, which claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 60/765,907, filed Feb. 7, 2006, entitled “Smart Cable Provisioning for a Patch Cord Management System,” and U.S. Provisional Patent Application Ser. No. 60/737,919, filed Nov. 18, 2005, entitled “Smart Cable Provisioning in Interconnect Applications for a Patch Cord Management System”, both of which are incorporated herein by reference in their entirety. The present application also incorporates by reference in its entirety U.S. patent application Ser. No. 11/265,316, filed Nov. 2, 2005, entitled “Method and Apparatus for Patch Panel Patch Cord Documentation and Revision.” 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to network documentation and revision systems and more particularly relates to a system for using patch cables having identification information to enable the provision of cable installation and removal instructions to a network technician and further to provide accurate network monitoring documentation. 
       BACKGROUND 
       [0003]    Patch panels are used in communications networks as intermediate elements between horizontal cabling (to which endpoint devices such as computers and telephones are connected) and network switches. When physical connections between endpoint devices and network switches are moved, added, or changed, patch panels are the points at which technicians complete the required moves, additions, or changes of cabling within patch fields. It is important to keep track of changes that are made to patch cord connections within the patch field. Proper documentation of changes in the patch field assures that the routing of patch cords is always known and further assures that any future changes are completed correctly. 
         [0004]    In interconnect network configurations, one patch panel is placed between the horizontal cabling and the network switch. In an interconnect configuration, the documentation of patch cord connections between the patch panel and the switch will provide the necessary documentation and monitoring of connections between the switch and the horizontal cabling. It is desirable to have a patch cord management system that enables complete documentation and monitoring of patch cord connections and that guides network installers as they make moves, adds, or changes to the patch cord connections. It is also desirable for a patch cord management system to have a minimal impact on existing networks. 
         [0005]    State-of-the-art patch cord documentation systems for interconnect applications require the addition of contact plates on printed circuit boards which are fastened to the front of switches and which have cables which connect the printed circuit boards to monitoring systems which scan 9 th  wire connections between the switch contact plates and contact plates on the front of an associated patch panel. This is typically a retrofit installation which requires a great variety of parts due to the great variety of switch configurations. 
         [0006]    The present invention is revolutionary because it works with any Ethernet switch without requiring any retrofit contacts. In addition, it monitors the patch cord configuration of a Network System in real time and provides immediate notice of any change. 
       SUMMARY OF THE INVENTION 
       [0007]    According to one embodiment of the present invention, a patch cord management system supports patch cord management in communications networks having an interconnect configuration. In one embodiment, patch cord identification information is electronically provided within a smart patch cord. The patch cord identification information can be read electronically by an intelligent patch panel, and each patch cord that is plugged into an intelligent patch panel is uniquely identifiable by the intelligent patch panel. The patch cord identification information can be associated with a switch and switch port, along with other physical information related to a data communication room, in a database. The provisioning of a smart patch cord and the association of the smart patch cord with an Ethernet switch and switch port are preferably done automatically. 
         [0008]    In one embodiment, indicator lights are provided to guide the installation and removal of patch cord connections. Indicator lights may be provided on patch cord plugs that are plugged into network switch ports. Indicator lights may also be provided near ports of an intelligent patch panel. 
         [0009]    According to another embodiment of the present invention, a patch cord management system supports patch cord management in communications networks. 
         [0010]    Patch cord management systems according to some embodiments of the present invention could be used in cross-connect networks. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0011]      FIG. 1  is a block diagram of a smart patch cord according to one embodiment of the present invention; 
           [0012]      FIG. 1   a  is a diagram of smart cable circuitry according to one embodiment of the present invention; 
           [0013]      FIG. 1   b  is a diagram of smart cable circuitry according to one embodiment of the present invention; 
           [0014]      FIG. 1   c  is a current-to-voltage plot of the circuit of  FIG. 1   b;    
           [0015]      FIG. 1   d  is a voltage-to-time plot of request and response signaling according to one embodiment of the invention; 
           [0016]      FIG. 1   e  is a diagram of smart cable circuitry according to one embodiment of the invention; 
           [0017]      FIG. 2  is a side view of a plug of a smart patch cord being plugged into a jack of an intelligent patch panel; 
           [0018]      FIG. 3  shows the construction of contacts on a port of an intelligent patch panel and on a plug of a smart patch cord, including a perspective view of the contacts of the smart patch cord; 
           [0019]      FIG. 4  is a perspective view of a plug of a smart patch cord for insertion into a port of a network switch; 
           [0020]      FIG. 5  is a front view of the plug of  FIG. 4 ; 
           [0021]      FIG. 6  is a rear view of the plug of  FIG. 4 ; 
           [0022]      FIG. 7  is a front view of an intelligent patch panel according to one embodiment of the present invention; 
           [0023]      FIG. 8  is a front view of an intelligent patch panel according to one embodiment of the present invention with a smart patch cord being plugged into a provisioning port during a patch cord addition; 
           [0024]      FIG. 9  is a front view of an Ethernet switch with a smart patch cord being plugged into a switch port during a patch cord addition; 
           [0025]      FIG. 10  is a front view of an intelligent patch panel with a smart patch cord being plugged into signal port during a patch cord addition; 
           [0026]      FIG. 11  is a front view of an Ethernet switch with a smart patch cord being unplugged during a patch cord removal 
           [0027]      FIG. 12  is a front view of an intelligent patch panel with a smart patch cord being unplugged during a patch cord removal; and 
           [0028]      FIG. 13  is a block diagram of a smart patch cord according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    The present invention is directed to methods and systems for monitoring, documenting, and guiding patch cord changes in a patch field of a communications network. The invention uses smart patch cords having unique identification information programmed into hardware within the smart patch cords.  FIG. 1  is a block diagram showing a smart patch cord  10  according to one embodiment of the invention. The smart patch cord  10  has a patch panel plug  12  for insertion into a port  31  of an intelligent patch panel and a switch plug  14  for insertion into a network switch such as an Ethernet switch. In the embodiment shown in  FIG. 1 , the smart patch cord  10  includes ten wires. The first through eighth wires  16  are Ethernet communication wires and they terminate at RJ-45 plugs  18  (as shown in  FIGS. 2 and 4 ) at the patch panel plug  12  and the switch plug  14  ends of the smart patch cord  10 . The ninth wire  20  and the tenth wire  22  of the smart patch cord  10  have different terminations on their two ends. At the patch panel plug end, the ninth and tenth wires  20  and  22  terminate at first and second contact plates  24  and  26  (as shown in  FIG. 3 ). At the network switch plug end, the ninth and tenth wires  20  and  22  terminate at a pogo switch assembly  28  provided within the network switch plug  14  of the smart patch cord  10 . The port  31  of the intelligent patch panel may comprise a jack  30  and ninth and tenth contacts  32  and  34 . 
         [0030]    Turning now to  FIG. 2 , a side view of a patch panel plug  12  of a smart patch cord  10  being plugged into a modular jack  30  of an intelligent patch panel port  31  is shown. In the RJ-45 jack embodiment shown, the modular jack  30  contains eight contacts that are electrically connected to the first through eighth wires  16  of the smart patch cord  10 . In addition, the first and second contact plates  24  and  26  of the patch panel plug  12  contact ninth and tenth contacts  32  and  34  associated with the intelligent patch panel port  31 .  FIG. 3  shows the first and second contact plates  24  and  26  of the patch panel plug  12  being inserted between the ninth and tenth contacts  32  and  34  of the intelligent patch panel port  31 . The ninth and tenth contacts  32  and  34  of the intelligent patch panel port  31  are arranged to maintain contact with the first and second contact plates  24  and  26 , respectively, while the patch panel plug  12  is connected to the intelligent patch panel port  31 . The first and second contact plates  24  and  26  are separated by an insulator layer  25 . 
         [0031]    The operation of the switch plug  14  of the smart patch cord  10  will now be described. As shown in  FIG. 1 , the smart patch cord  10  includes LEDs and control circuitry  15 , identification circuitry  17 , and plug detection circuitry  19 . The LEDs and control circuitry  15  provide LEDs on the switch plug  14  and also allow for control of the LEDs. The identification circuitry  17  allows each smart patch cord  10  in a network to be uniquely identified. The plug detection circuitry  19  allows for detection of when the smart patch cord  10  is plugged into an Ethernet switch port. In the embodiment of  FIG. 1 , all these circuits are provided in the switch plug  14 , but circuits may be located in other parts of the smart patch cord  10 . Specific circuit designs for the LED control circuitry  15 , the identification circuitry  17 , and the plug detection circuitry  19  will now be shown and described with reference to  FIGS. 1   a - 1   e.    
         [0032]    The switch plug  14  has a pogo pin  36  that is spring-biased to an outward position as shown in  FIG. 4 . In the embodiment of  FIG. 1   a , the pogo pin  34  operates a normally open switch  38  so that when the pogo pin  36  is pushed into the pogo switch assembly  28  upon insertion of the switch plug  14  into a switch port, the normally open switch  38  of the pogo switch assembly  28  is closed. This enables the intelligent patch panel to determine when the switch plug  14  has been plugged into a switch port. In the embodiment of  FIG. 1   a , the transistors Q 1 , Q 2 , and Q 3 ; resistors R 1 , R 2 , R 3 , and R 4 ; and LEDs  54   a  and  54   b  provide the functionality of the LEDs and control circuitry  15  as shown in  FIG. 1 . The ID integrated circuit  50 , diode D 1 , and resistor R 6  provide the functionality of the identification circuitry  17  as shown in  FIG. 1  by responding to an intelligent patch panel  40  (further shown and described below with reference to  FIG. 7 ) with an ID number when the intelligent patch panel  40  requests to read the ID. The circuitry  51  illustrated on the far left side of  FIG. 1   a  is a representative view of the circuitry of an intelligent patch panel  40 . 
         [0033]    It is desired that the LEDs and control circuitry  15  be able to selectively turn the green LED  54   a  or the red LED  54   b  on and not interfere with the functionality of the ID integrated circuit  50 . The embodiment shown in  FIG. 1   a  satisfies this requirement.  FIGS. 1   b  and  1   c  provide an example simulation of the LED control circuitry of  FIG. 1   a . The LEDs  54   a  and  54   b  are turned on with a reverse voltage applied to the ninth and tenth wires  20  and  22  of the smart patch cord  10 . This reverse voltage is labeled V in , in  FIGS. 1   a  and  1   b  (the reverse voltage circuitry in the intelligent patch panel  40  is not shown). For V in , less than V 1 , both LEDs  54   a  and  54   b  are essentially off. Here the input voltage is not high enough to provide enough current into the red LED  54   b  to make it very bright and the voltage is too low to turn Q i  on to even provide current to the green LED  54   a . The transistor Q 1  and resistors R 1  and R 2  implement a common circuit called a Vbe multiplier, which multiplies the base-emitter voltage of a transistor by the ratio of R 2 /R 1 . For input voltages V 1 &lt;V in &lt;V 2 , the red LED  54   b  is on and the green LED  54   a  still remains off Here the V in  provides enough voltage to produce enough current into the red LED  54   b  to turn it on brightly. The V in  within this range still is not large enough to provide enough current into the green LED  54   a . As the input voltage is increased such that V 2 &lt;V in &lt;V 3 , the red LED  54   b  is still on and now the green LED  54   a  begins to turn on. Once V in  exceeds V 3 , the green LED  54   a  stays on but the red LED  54   b  turns off because the current through R 2  produces a sufficient voltage across it to turn Q 2  on, which then turns on Q 3 . This diverts the current from the red LED  54   b  into Q 1  and thus turns the red LED  54   b  off. In order to operate this circuit effectively, three voltages (or states) must be defined: a voltage for which both LEDs are off (V off ), a voltage for when only the red LED  54   b  is on (V red ), and a voltage when only the green LED  54   a  is on (V green ). An example definition of these voltages is shown below:
       0.5 V&lt;V off &lt;1V both LEDs off   2.0 V&lt;V red &lt;2.5 V only the red LED  54   b  is on   V green &gt;4.25 V only the green LED  54   a  is on.       
 
         [0037]    The integrated circuit (IC)  50  that provides the identification (ID) number of the smart patch cord  10  at the request of the intelligent patch panel  40  is implemented in  FIG. 1   a  and can have the protocol as shown in  FIG. 1   d . In  FIG. 1   d , a forward voltage (e.g., 5 V) is applied to the IC  50 , and when the intelligent patch panel  40  requests an ID number from the smart patch cord  50 , the intelligent patch panel  40  drives the input low and back high in a defined manner such that the IC  50  recognizes this as an ID number request. The IC  50  responds with a series of high-to-low transitions that represent the ID number. This protocol has been implemented and defined in the industry. One such example is the ONE-WIRE™ protocol developed by the Dallas Semiconductor corporation, and an example of an IC that could be used for IC  50  is the DALLAS SEMICONDUCTOR DS2401 IC. The data sheet for this semiconductor, entitled “DS2401 Silicon Serial Number,” Dallas Semiconductor Publication No. 022102, is incorporated herein by reference in its entirety. The diode D 1  in the circuitry shown in  FIG. 1   a  is included to prevent damage to the IC  50  and to prevent interference by the ID circuitry  17  with the LEDs and control circuitry  15  and the plug detection circuitry  19 . The diode D 1  effectively eliminates the IC  50  from the circuit when reverse voltages (to operate the LEDs and control circuitry  15  and the plug detection circuitry  19 ) are applied. Such a reverse voltage, with wire ten at a higher potential than wire  9 , is shown in  FIG. 1   a . The diode D 1  allows the IC  50  to operate when a forward voltage is applied across wires nine and ten, and the LEDs and control circuitry  15  and the plug detection circuitry  19  are effectively removed from the circuit when a forward voltage is applied. The resistor R 6  ensures that the diode D 1  is sufficiently turned on when a forward voltage is applied. 
         [0038]    The switch  38  of  FIG. 1   a  is a normally open switch that allows the intelligent patch panel  40  to detect when the switch plug  14  is inserted into an Ethernet switch port  72 . The switch  38  is a “pogo” style switch such that when the switch plug  14  is inserted into the Ethernet jack, the pogo pin  36  (as shown in  FIG. 4 ) is depressed and the switch  38  closes. The intelligent patch panel  40  continuously monitors the smart patch cords connected to it and if it detects that resistor R 5  is present in the circuit, the intelligent patch panel  40  will determine that the patch cord is inserted into the Ethernet switch. If the resistor R 5  is not detected by the intelligent patch panel  40 , the intelligent patch panel  40  will determine that the patch cord is not inserted into an Ethernet switch. The diode D 2  allows current to flow through the resistor R 5  only when a reverse voltage is applied across wire nine  20  and wire ten  22  (i.e., wire ten  22  is at a higher potential than wire nine  20 ). 
         [0039]    The LEDs and control circuitry  15  cause three different magnitudes of current to flow in wires  20  and  22  corresponding to the three different voltage levels which determine the state of the LEDs. When pogo switch  38  is closed, each of the three different voltage levels which determine the state of the LEDs cause three different currents to flow through the switch  28  and the resistor R 5 , and these currents also flow through wires  20  and  22 . 
         [0040]    The intelligent patch panel correlates the reverse voltage applied to wires nine and ten with the total current flowing through them to determine if the switch plug  14  is plugged into a switch port  72 . If no current is flowing through wires nine and ten when a reverse voltage is applied, the intelligent patch panel concludes that no smart patch cord is plugged into a patch panel port  31  or  60 . A reverse voltage is constantly applied except when a patch cord ID is being read with a forward voltage. 
         [0041]      FIG. 1   e  shows another embodiment of the circuitry of the smart patch cord  10 . In the embodiment of  FIG. 1   e , the LED control circuitry is slightly different from the circuitry shown in  FIG. 1   a . The LED control circuitry of  FIG. 1   e  operates in a reverse voltage mode similarly to the circuitry of  FIG. 1   a , except that the LEDs  54   a  and  54   b  are controlled differently. In the embodiment shown in  FIG. 1   e , at a sufficiently low voltage, both LEDs  54   a  and  54   b  will remain off. At a higher input voltage V in , the red LED  54   b  will turn on, but the voltage will be too low for both the diode D 2 ′ of  FIG. 1   e  and the green LED  54   a  to turn on. At a still higher input voltage V in , the red LED  54   b  will remain on and the voltage will be sufficiently large for the green LED  54   a  to also turn on. When both the green LED  54   a  and the red LED  54   b  are on, if one mixes the resulting light, it will appear to the user as amber in color. If one does not mix the resulting light, the fact that both the red LED  54   b  and the green LED  54   a  are on can be used to signify an event. Hence, three states will exist for the LEDs in the embodiment of  FIG. 1   e : (1) both LEDs off; (2) red LED  54   b  on; and (3) both LEDs on. In the embodiment of  FIG. 1   e , the switch  38 ′, which allows the intelligent patch panel  40  to detect when the switch plug  14  is plugged into a switch port, is a normally open switch. 
         [0042]    The physical aspects of the switch plug  14  are further shown in  FIGS. 4 ,  5 , and  6 .  FIG. 4  is a perspective view of an unplugged switch plug  14 , with the pogo pin  36  in its extended position.  FIGS. 5 and 6  show front and rear views, respectively, of the switch plug  14 . First through eighth contacts  52  of the switch plug  14  correspond to first through eighth wires of the smart patch cord. As shown in  FIG. 6  and as further described below, light-emitting diodes (LEDs)  54   a  and  54   b  are provided on the switch plug  14  and are visible from the rear. According to one embodiment, the LEDs of the switch plug  14  are a green LED  54   a  and a red LED  54   b . The first through eighth wires  16 , the ninth wire  20 , and the tenth wire  22  of the smart patch cord may be provided as a five-pair cable  56  that is terminated at the switch plug  14 . 
         [0043]      FIG. 7  is a front view of an intelligent patch panel  40  for use with the smart patch cord  10 . The intelligent patch panel  40  illustrated in  FIG. 7  has 24 signal ports  31   a - 31   x  on its front face. A network management system (NMS) Ethernet connection  58  connects to a management port of the intelligent patch panel  40  and allows the intelligent patch panel  40  to communicate with a network management system. A provisioning port  60  is also provided on the face of the intelligent patch panel  40 . Each of the signal ports  31   a - 31   x  has an associated smart cord contact assembly  62 , comprising the ninth and tenth contacts  32  and  34  associated with each of the ports  31   a - 31   x . Each signal port  31   a - 31   x  also has an associated LED  64   a - 64   x . The provisioning port  60  has an LED  66 , an associated push button switch  68 , and a smart cord contact assembly  69 . 
         [0044]    The push button switch  68  is used to provide information to the user as to where patch cords are connected. This can be done by lighting LEDs that represent the two connecting ends of patch cords for cross-connect and interconnect applications. According to one embodiment, when the user pushes the push button switch  68  once, the LED  64   a  associated with the first signal port  31   a  will light, and so will an LED (for example, LED  54   a  or  54   b ) in the switch plug  14  of the smart patch cord  10  that is plugged into the first signal port  31   a . When the user pushes the push button switch  68  a second time, the LED  64   b  associated with the second signal port  31   b  will light, and so will an LED in the switch plug  14  of the smart patch cord that is plugged into the second signal port  31   b . Likewise, in cross-connect applications, LEDs associated with both ends of each patch cord can be lighted in this manner. The user may terminate this process, for example, by pushing the push button switch  68  twice rapidly or by holding down the push button switch  68 . 
         [0045]    The provisioning port  60  is preferably located near the center of the face of the intelligent patch panel  40  to reduce problems with patch cord lengths, though an alternative end location is shown in  FIGS. 8 ,  10 , and  12 . The intelligent patch panel  40  may have a separate power connection (not shown), or it may receive power via power-over-Ethernet through the NMS connection  58 . The intelligent patch panel  40  includes processing circuitry, communication circuitry, and memory that enable it to perform the functions described below. 
         [0046]      FIGS. 8-10  illustrate how the intelligent patch panel  40  works in conjunction with a smart patch cord  10  to guide an installer in the addition of a patch cord to a network. The intelligent patch panel  40  is located near an Ethernet switch  70  in an interconnect network, preferably in a data closet. In order to guide the addition of a patch cord connection between the intelligent patch panel  40  and the Ethernet switch  70 , first a work order to add a new patch cord is issued. The locations of the ports to which to connect the new patch cord may be displayed on a display in the data closet. In addition, LEDs of the switch plug  14  and of the ports of the intelligent patch panel  40  signal operations to be performed by the installer. These LED signals are as follows:
       On: Add a plug   Flashing; Remove a plug   Green: Normal Operation   Red: An error has been made.       
 
         [0051]    To begin the addition of a patch cord to the network, the installer plugs the patch panel plug  12  of the smart patch cord  10  into the provisioning port  60  of the intelligent patch panel  40 , as shown by the arrow “A” of  FIG. 8 . The provisioning port  60  will have its associated LED  66  lit in solid green to guide the installer. After the patch panel plug  12  has been inserted into the provisioning port  60 , the green LED  66  of the provisioning port turns off and the intelligent patch panel  40  reads the identification number of the identification circuit  50  (as shown in  FIG. 1 ) through the ninth and tenth wires of the smart patch cord  10 . The intelligent patch panel  40  also sends a signal through the smart patch cord  10  to light the green LED  54   a  on the switch plug  14  (as shown in  FIG. 9 ). The installer then plugs the switch plug  14  into the appropriate port  72  of the Ethernet switch  70 , as shown by the arrow “B” of  FIG. 9 . This initiates the intelligent patch panel provisioning operation. 
         [0052]    When a patch cord connected to the provisioning port  60  is connected to a switch port, the intelligent patch panel  40  sends a message which includes the patch cord ID number to the NMS through the patch cord and the switch port. The NMS then determines which switch and switch port this message was received on by reading the routing tables in the Ethernet switch. Prior to sending the message that includes the ID number, the intelligent patch panel may send an Ethernet Link-Up message to the NMS that the network management system will interpret as the addition of a new patch cord, and the NMS may send a Simple Network Management Protocol (SNMP) message to the intelligent patch panel requesting the ID number of the new smart patch cord. If the switch plug  14  is plugged into the correct port  72  of the Ethernet switch  70 , the green LED  54   a  turns off If the switch plug  14  is plugged into the wrong switch port, the red LED  54   b  will flash. 
         [0053]    If the intelligent patch panel provisioning operation is successful, the provisioning port LED  66  will flash green until the patch panel plug  12  is removed from the provisioning port  60 . If the operation fails, the provisioning port LED  66  will flash red and the installer should retry the operation. If the operation fails after the retry, the smart patch cord  10  can be programmed manually. 
         [0054]    After the patch panel plug  12  is removed from the provisioning port  60  following a successful provisioning operation, an LED associated with the intelligent patch panel signal port into which the patch panel plug  12  is to be inserted will turn on solid green or will flash green. In the example shown in  FIG. 10 , the patch panel plug  12  is to be plugged into the seventeenth signal port  31   q  of the intelligent patch panel  40 , and the seventeenth patch panel port LED  64   q  turns on solid green to indicate the designated port to the installer. The installer plugs the patch panel plug  12  into the designated port, as shown by the arrow “C” of  FIG. 10 . If the addition of the smart patch cord  10  is successful, the LED  64   q  will turn off. If the patch cord  10  is plugged into the wrong port, the wrong port&#39;s associated LED will flash red and the installer must take the patch cord out of the wrong intelligent patch panel signal port and locate the designated signal port adjacent to the activated green LED  64   q . When a patch cord is plugged into any signal port, the intelligent patch panel will read the ID number of the patch cord to ensure it is the correct patch cord. If it is not the correct patch cord, the LED  64  of that port will flash red and the patch cord plug must be removed from that port. 
         [0055]      FIGS. 11 and 12  illustrate the process of removing a smart patch cord  10  that is connected between an intelligent patch panel  40  and an Ethernet switch  70 , preferably within a data closet. First, a work order to remove a patch cord is issued. The locations of the ports from which to disconnect the patch cord are displayed on a display in the data closet. The installer is guided to the Ethernet switch side of the smart patch cord  10  first by an LED  54   a  on the switch plug  14 . The LED  54   a  may flash green to indicate to the installer that the switch plug  14  is to be removed. The installer then removes the switch plug  14  from the Ethernet switch port  72 , as shown by the arrow “D” of  FIG. 11 . Upon successful removal of the switch plug  14  from the correct switch port  72 , the LED  54   a  turns off. If the LED  54   b  turns red following removal of the switch plug, that indicates that the switch plug was removed from the wrong port. If this occurs, that patch cord must be removed from the intelligent patch panel  40  and the patch cord addition procedure must be followed. When the patch cord has been correctly removed from the Ethernet switch  70 , the intelligent patch panel  40  sends a message to the NMS indicating which patch cord was removed. Once the smart patch cord  10  is removed from the Ethernet switch  70 , an NMS database disassociates the identification number of the smart patch cord from the Ethernet switch port to which it had been connected. 
         [0056]    To continue the removal process for the smart patch cord  10 , as shown in  FIG. 12 , the installer is guided to the intelligent patch panel  40  by the intelligent patch panel port LED  64   q  that is associated with the port from which the smart patch cord  10  is to be removed. The LED  64   q  flashes green to indicate the designated signal port. The installer then removes the patch panel plug  12  from the patch panel designated signal port  31   q , as shown by the arrow “E” of  FIG. 12 . If the patch panel plug  12  was removed correctly, the LED  64   q  will turn off, indicating success. If the LED  64  turns red upon removal of the patch panel plug  12 , this indicates that the incorrect patch panel plug was removed and the installer should reinsert the removed plug and remove the designated plug as indicated by a flashing green LED  64   q . If any patch cord addition or removal function which has started has not been successfully completed, no additional such functions will be ordered until the problem has been resolved. 
         [0057]      FIG. 13  is a block diagram showing a smart patch cord  100  according to another embodiment of the invention. The smart patch cord  100  operates in a manner similar to that described above, thus the indicator lights are not shown. An intelligent patch panel can detect whether the switch plug  114  of the smart patch cord  100  is plugged into a switch port by performing resistance measurements on the ninth and tenth wires  120  and  122  of the smart patch cord  100  without interfering with signal wires  116 . The pogo switch assembly  128  will result in different resistance measurements reflecting the plugged or unplugged status of the switch plug  114 . The intelligent patch panel initiates status detection for a smart patch cord  100  by placing a voltage across the ninth and tenth contacts  32  and  34  associated with the intelligent patch panel port  31 . The intelligent patch panel then makes resistance measurements across the ninth and tenth contacts  32  and  34 . If a very high resistance is measured across the ninth and tenth contacts  32  and  34 , the condition is determined to be an open circuit between the ninth and tenth contacts  32  and  34  and the intelligent patch panel determines that no smart patch cord is plugged into the associated port of the intelligent patch panel. 
         [0058]    To detect the plugged or unplugged status of the switch plug  114  of a smart patch cord  100  that is plugged into the port  31  of the intelligent patch panel, the intelligent patch panel places forward and reverse voltages on the ninth and tenth wires  120  and  122  to perform forward and reverse resistance measurements. In the forward measurement, a voltage is placed across the ninth and tenth wires  120  and  122  so that the ninth wire  120  has the higher potential. In the reverse measurement, a voltage is placed across the ninth and tenth wires  120  and  122  so that the tenth wire  122  has the higher potential. 
         [0059]    If the switch plug  114  of the smart patch cord  100  is unplugged, the normally open switch  138  will be open. Thus, in the forward measurement (with the ninth wire  120  being at a higher potential than the tenth wire  122 ), a high resistance will result across the ninth and tenth contacts  32  and  34  of the port  31  because current will flow through both the first and second plug presence detection resistors  142  and  144 , which are connected in series. The measured resistance in the forward measurement will be R=R 1 +R 2 . In the reverse measurement (with the tenth wire  122  being at a higher potential than the ninth wire  120 ), a low resistance will be measured across the ninth and tenth contacts  32  and  34  of the port  31  because current will flow through the reverse detection resistors  146  (which are connected in parallel with the series connection between the first and second plug detection resistors  142  and  144 ) in addition to the first and second plug presence resistors  142  and  144 . Diodes  148  ensure that current will flow through the reverse detection resistors  146  in parallel with the series connection between the first and second plug resistors  142  and  144  only during the reverse measurement process and not during the forward measurement process. 
         [0060]    If the switch plug  114  of the smart patch cord  100  is plugged into a network switch, the normally open switch  138  will be closed. Thus, in the forward measurement, a lower resistance will result across the ninth and tenth contacts  32  and  34  of the port  31  because current will flow only through the first plug presence detection resistor  142 , with the closed switch  138  effectively shunting the second plug presence detection resistor  144  out of the circuit. The measured resistance in the forward measurement will be R=R 1 . In the reverse measurement, with the normally open switch  138  being closed, again a lower resistance will be measured because current will also flow through the reverse detection resistors  146 , which are connected to the circuit in parallel. The identification circuit  150  is also included in the pogo switch assembly  128 . Similar to the embodiment shown in  FIG. 1   e , the detection circuitry contains only passive elements. 
         [0061]    The principles of the present invention may be applied to other specific systems. For example, patch cords according to other embodiments of the present invention are designed for use in optical communication networks or in other electrical communication networks that do not employ RJ-45 plugs and jacks. The present invention may also be applied in a cross-connect application. 
         [0062]    It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. For example, “a” may denote the use of one or more elements. The lists presented herein are intended to be exemplary rather than limiting. Also, variations presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, and are also intended to be encompassed by the following claims.