LAN Cabling Certification
Glossary - LAN Cabling Certification Wire map
Provides a visual map of how the con- nections on either side of a multicore cable are connected together.
Near end
The part of the cable which is closest to the master test engineer.
Far end
The part of the cable which is furthest away from the master test engineer.
Crosstalk Crosstalk occurs when the magnetic field generated by a pairs of wires cre- ates interference on another pair of wires. Crosstalk is sometimes abbrevi- ated to “XT”.
Near End Crossover Talk (NEXT) NEXT function monitors the effect send- ing 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 com- pared to the induced signal provides the NEXT value. NEXT tests should be per- formed 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 stand- ard cable will contain 8 wires. PSNEXT looks at the effect of sending signals down three pairs of wires has on the pair of wires under test. This is calcu- lated by performing a NEXT test on each pair of wires and then summing all the values together 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 func- tion can be used.
Far End Crossover Talk (FEXT) FEXT looks at the effect a signal in- duced 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 representa- tion of the wires).
Power Sum Equal Level Far End Cross- over Talk (PSELFEXT)
PSELFEXT 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 ELFEXT test
on each pair of wires and then summing all the values together 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 fibre.
Attenuation to Crosstalk Ratio (ACR) The difference between attenuation and crosstalk, measured in dB, at a given fre- quency. 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 having 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 multicore cable, where each pair has their own propagation delay time, the delay skew is the difference between the first signal arriving and the last signal arriving.
5. 2
Accessories: page 5.07
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