Copper Cabling Test Tools

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• Once you have terminated cable, you must test it to ensure that each wire makes good electrical contact and is in the correct pin position
• best time to verify wiring installation and termination is just after you have made all the connections
  • you should still have access to the cable runs
  • Identifying and correcting errors at this point will be much simpler than when you are trying to set up end user devices

Cable Tester

A cable tester reports detailed information on the physical and electrical properties of the cable.

• pair of devices designed to attach to each end of a cable
• It can be used to test:
  • a patch cord
  • can be connected via patch cords to a wall port and patch panel port to test the permanent link
• The tester energizes each wire in turn, with an LED indicating successful termination
• If an LED does not activate
  • the wire is not conducting a signal, typically because the insulation is damaged or the wire isn’t properly inserted into the plug or IDC
• If the LEDs do not activate in the same sequence at each end
  • the wires have been terminated to different pins at each end
  • Use the same type of termination on both ends
• tests and reports:
  • cable conditions
  • crosstalk
  • attenuation
  • noise
  • resistance
• certifiers can test and certify a cable’s performance category

Wire Map Testers

• a wire map tester device can detect improper termination issues
  • to perform a wire map test:
    • base unit is connected to one end of the cable and a remote unit to the other
    • test is activated, an LED for each wire conductor lights up in sequence
    • If an LED fails to light or does not light in sequence,
      • there is a problem with the cable and/or termination
  • can identify the following problems:
    • continuity (open) — conductor does not form a circuit because of cable damage or the connector is not properly wired
    • short — two conductors are joined at some point, because the insulating wire is damaged, or a connector is poorly wired
    • incorrect pin-out/incorrect termination/mismatched standards
      • conductors are incorrectly wired into the terminals at one or both ends of the cable
      • common transpositions:
        • reversed pair — conductors in a pair have been wired to different terminals
          • e.g., pin 3 to pin 6, etc
        • crossed pair (TX/RX transposed — conductors from one pair have been connected to pins belonging to a different pair
          • e.g., pins 3 and 6 to pins 1 and 2
          • may be done deliberately to create a cross-over cable
            • would not be used to link a host to switch
    • split pair — both ends of a single wire in one pair are wired to terminals belonging to a different pair
      • only detected by a cable tester that measures crosstalk

Tone Generator and Toner Probe

• Many cable testers also incorporate the function of a toner probe
• a tone generator (toner) and probe are used to trace a cable from one end to the other
  • used to identify a cable from within a bundle
    • when the cables have not been labeled properly
  • aka fox and hound
  • The tone generator is connected to the cable using an RJ45 jack
    • applies a continuous audio signal on the cable
  • probe is used to detect the signal and follow the cable over ceilings and through ducts or identify it from within the rest of the bundle
• Disconnect the other end of the cable from any network equipment before activating the tone generator

Loopback Plug

• A loopback plug is used to test a NIC or switch port
• can make a basic loopback plug from a 6” cable stub where the wires connect pin 1 to pin 3 and pin 2 to pin 6
• When you connect a loopback plug to a port, you should see a solid link LED showing that the port can send and receive

Info

A loopback plug made from a cable stub is unlikely to work with Gigabit Ethernet ports. You can obtain manufactured Gigabit port loopback testers.