2.5.2 Copper Wiring Troubleshooting Facts

Question 1

EMI/RFI

Answer 1

• Are external signals that interfere with normal network communications
• Common sources of EMI/RFI include generators, motors, radio transmitters, welders, transformers, and fluorescent lighting.

Question 2

How to protect against EMI/RFI

Answer 2

• Use fiber
• Use shielded twisted pair cables
• Avoid installing cables near EMI/RFI sources

Question 3

Crosstalk

Answer 3

• Interference caused by signals within the twisted pair of wires

Question 4

Near-end Crosstalk

NEXT

Answer 4

• Measured on the same end as the transmitter.
• Ex. when a signal is sent on one wire pair near-end crosstalk measures the interference on an adjacent wire pair at the same connector end.

Question 5

Far-end Crosstalk

Answer 5

• Is measured on the end without the transmitter,
• Ex when a signal is sent on one wire pair, far-end crosstalk measures the interference on the adjacent wire pair at the opposite connector end

Question 6

Alien Crosstalk

Answer 6

• Is introduced from adjacent parallel cables
• Ex. a signal sent on one wire pair causes interference on a wire pair that is within a separate twisted pair cable bundle

Question 7

Attenuation

Answer 7

• Is the loss of signal strength from one end of the cable to the other
• Also know as dB loss

Question 8

Attenuation Facts

Answer 8

• The longer the cable the more attenuation (reason why it is important not to exceed maximum cable length
• Cables at higher temps experience more attenuation
• A repeater regenerates the signal and removes the effects of attenuation

Question 9

Open Impedance Mismatch (Echo)

Answer 9

• Is the measure of resistance within the transmission medium

Question 10

Open Impedance Mismatch (Echo)

Answer 10

• Impedance is measured in ohms
• All cables must have the same impedance rating
• Impedance is mostly a factor in coaxial cables
• Cable distance does not affect the impedance of the cable

Question 11

Short

Answer 11

• An electrical short occurs when electrical signals take a path other than the intended path

Question 12

Open Circuit

Answer 12

• When a cut in the wire prevents the original signal from reaching the end of the wire

Question 13

Mis-wired Cable

Answer 13

• Caused by incorrect wire positions on both connectors

Question 14

Mis-wired cable causes

Answer 14

• Reverse Connection

* Split Pair

Question 15

Reverse Connection

Answer 15

• When a cable is wired using one standard on one end and another standard on the other

Question 16

Split Pair

Answer 16

• A condition when a a single wire in two different pairs is reversed at both ends

Question 17

Incorrect Termination

Answer 17

• Occurs when an incompatible or incorrect connector is used

Question 18

Bad Connector

Answer 18

• A damaged connector that is causing connectivity issues

Question 19

Transceiver Mismatch

Answer 19

• Well-manufactured network devices have interfaces that can be tailored to different cable types, protocols, and speeds.
• This is done by connecting a hot swappable transeiver to the interface. When connecting one network device to another, matching transceiver must be used. For twisted pair cabling, a mismatch in speed is a common issue.