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Figure 9-8: T568A and T568B Pin / Pair Assignments
Eight-conductor data cable (Cat 3 or Cat 5e) contains 4 pairs of wires. Each pair consists of a solid color
wire and a white and color striped wire. The pairs designated for 10BaseT Ethernet are orange and green.
The other two pairs, brown and blue, are unused. The connections shown are specifically for an RJ45 plug.
The wall jack may be wired in a different sequence because the wires may be crossed inside the jack. The
jack should either come with a wiring diagram or at least designate pin numbers matching the color code
Performance Verification and Testing
Alien Crosstalk: Unwanted signal coupling from one component, channel, or permanent link to
another is defined as alien crosstalk. Since alien crosstalk is an indicator of differential (or balanced)
signal coupling, alien crosstalk cannot be adversely impacted by common mode noise (e.g. noise
from motors or florescent lights) that is present in the environment. Alien crosstalk is only specified
by the Standards as a power sum parameter for components and cabling to approximate the energy
present when all pairs are energized. Power sum alien crosstalk measured at the near-end is called
“power sum alien near-end crosstalk loss (PSANEXT loss)” and power sum alien crosstalk
measured at the far-end is called “power sum alien attenuation to crosstalk ratio, far-end
(PSAACRF)”. High power sum alien crosstalk levels can compromise the operation of the
Balance: Twisted-pair transmission relies on signal symmetry or “balance” between the two
conductors in a pair. Maintaining proper balance ensures that cabling systems and components do
not emit unwanted electromagnetic radiation and are not susceptible to electrical noise. Component
balance requirements are specified for category 6/class E cabling. Component and cabling balance
requirements are specified for category 6A/class EA and higher grades of cabling. Balance may be
characterized by longitudinal conversion loss (LCL), longitudinal conversion transfer loss (LCTL),
transverse conversion loss (TCL), or equal level transverse converse transfer loss (ELTCTL).
Insertion Loss (Attenuation): Insertion loss is a measure of the decrease in signal strength along the
length of a transmission line. Ensuring minimal signal attenuation is critical because digital signal
processing (DSP) technology can not compensate for excessive signal loss.
Near-End Crosstalk (NEXT) Loss: Pair-to-pair near-end crosstalk (NEXT) loss quantifies
undesired signal coupling between adjacent pairs at the near-end (the same end as the transmit-end)
of cabling or a component. Excessive NEXT loss can be especially detrimental to applications that
do not employ crosstalk cancellation digital signal processing (DSP) technology.
Power Sum: All pair-to-pair crosstalk parameters can be expressed as a power summation, which
approximates the level of undesired internal signal coupling present when all pairs are energized.
Power sum NEXT loss, ACRF, ANEXT loss, and AACRF characterization confirms that the
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