Cable Characteristics - ActionTec V2000H Manual

1.2 Cable Characteristics

All cable has certain characteristics which will determine its operational parameters. In this section, you will
learn of the most important characteristics of copper cable.
Balance

A balanced cable is one in which both conductors are of the same type and have equal impedance to
ground or other circuits. Twisted Pair cabling are balanced cables whereas coax is usually
unbalanced.
EMF Shielding

In an attempt to eliminate or at least reduce the effects of noise and interference from outside
electrical sources, many cable types use some kind of shielding around the cable or even around
individual conductors.

This shielding is often in the form of aluminum foil, which is wrapped around the cable or around
individual pairs.

In Coax cable, the outer conductor, which is comprised of a cylinder of braded copper or aluminum
strands, servers as the shield

The twists in twisted pair cable serve as shielding, reducing the effect of Electro Magnetic Field (EMF)
interference, which is caused by the electrical field of nearby conductors such as electrical wires, or
even other telephone or data cables.
Attenuation
The reduction in signal strength along the length of a conductor. As the strength of a signal declines,
the ability for a receiver to distinguish between the signal and the noise on the cable is impaired. At
some point, the signal and the noise will be indistinguishable.
Noise

Caused by unwanted electrical impulses on the conductor as well as by the metallic nature of the
conductor itself.

Metallic or Gaussian Noise

Is caused by the constant movement of electrons in a copper conductor or idle electrical
circuit. This is the noise you will hear if you turn up the volume on a stereo that has no
signal. Metallic noise is typically disregarded in telephone circuits.

Impulse Noise

Is created by spurious electrical signals that are typically short lived. A lightning strike, the
start of a furnace, or even turning on a light switch, can all cause a short lived electrical
impulse to effect a conductor. In a telephone circuit, this is often perceived as a "pop" or
"crackle" that comes and goes in a short time period.

Electro Magnetic Interference (EMI)

Is noise that is of longer or even constant duration, and which is caused by EMF interference
from other electrical sources.
Cross Talk

EMI from other conductors, whether from the same cable pair or adjacent pairs.

The twists, in twisted pair cable, help to reduce the effects of crosstalk.

Each pair in a 25 pair cable has a different twist so this eliminates the crosstalk greatly.

Other Digital circuits, special circuits and/or DSL circuits in the same cable will affect each other.
Some having greater affects than others.
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