LAN Cabling Certifi cation
Glossary - LAN Cabling Certifi cation Wire map
Provides a visual map of how the connections on either side of a multi- core cable are connected together.
Near end
The part of the cable which is clos- est to the master test engineer.
Far end
The part of the cable which is fur- thest away from the master test en- gineer
Crosstalk
When the magnetic fi eld generated by a pairs of wires creates interfer- ence on another pair of wires. This is sometimes abbreviated to “XT”
Near End Crossover Talk (NEXT) NEXT monitors the effect sending a signal down one set of wires has on a second set of wire. Leaving the far end of the wires open, a signal is sent down one pair of wires and the induced signal is measured on the second set of wire. The ratio of the sent signal compared to the induced signal provides the NEXT value. NEXT tests should be performed at both sides of the cable. If a remote unit is used, one unit can check the transmitting side of the cable and by setting the MultiLAN to “Remote NEXT” test, the other side of the cable can be tested without the test engineer having to move location.
Power Sum Near End Cross Talk (PSNEXT)
In most modern LAN systems, a standard cable will contain 8 wires. PSNEXT looks at the effect of send- ing signals down three pairs of wires has on the pair of wires under test. This is calculated by performing a
5. 2
NEXT test on each pair of wires and then summing all the values togeth- er to create the PSNEXT value for the pair of wires under test. In most cases, the PSNEXT test should be performed from both sides of the cable, hence the “Remote PSNEXT” test function can be used.
Far End Crossover Talk (FEXT) FEXT looks at the effect a signal induced into one pair of wires will have on a receiver connected to a second pair of wires. To perform the test, a signal placed onto a single pair of wires and the signal on the other set of wires is measured at the other end of the cable.
Equal level far end crossover talk (ELFEXT)
ELFEXT is a FEXT test which takes into account the attenuation of the wires (providing a more realistic rep- resentation of the wires)
Power sum equal level far end crossover talk (PSELFEXT) In most modern LAN systems, a standard cable will contain 8 wires. PSELFEXT looks at the effect of sending signals down three pairs of wires has on the pair of wires under test. This is calculated by performing a ELFEXT test on each pair of wires and then summing all the values to- gether to create the PSELFEXT value for the pair of wires under test.
Attenuation
The loss of strength in a signal as it is transmitted over a cable or fi bre
Attenuation to crosstalk Ratio (ACR)
The difference between attenua- tion and crosstalk, measured in dB,
at a given frequency. The higher the ACR value is, the better the signal is at the receiving end compared to the crosstalk interference signal. The ACR value should be taken at both ends of the cable, hence the “Remote ACR” function is provided to stop the engineer continually hav- ing to move the master unit between locations.
Propagation delay
The time it takes for a signal to pass from one side of the cable to the other.
Delay Skew
In multi-core cable, where each pair has their own propagation delay time, the delay skew is the differ- ence between the fi rst signal arriv- ing and the last signal arriving.
Accessories: page 5.08
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