Terminology for data cable technology 
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ACR
(Attenuation to crosstalk ratio)
 An important factor for transmission quality is the ratio of the desired signal to the interference signal. In order to guarantee flawless transmission, the interference signal derived from crosstalk attenuation must be smaller by a specific factor.
This corresponds to the difference between the crosstalk attenuation and the link attenuation.
ACR [dB] = NEXT [dB]  -a [dB]; (a =attenuation).
Attenuation 
(Wave attenuation, cable attenuation)
 Attenuation is depended on the resistance per length unit R' (conductor resistance) and the capacitance per length unit C' (mutual capacitance). It increases approximately with the square root of the frequency up to 50 MHz, and linearly for higher frequencies. The attenuation is increasing lineary with the length.
Conductance per length unit G' Conductance per length unit describes the isolation loss, dielectric loss as well as the corona loss between the conductors. Instead of the often strongly frequency dependent conductance per length unit G', the loss factor theta is specified. The size of the loss factor depends on isolation, on isolation design, and on frequency and temperatur. In general theta should be as small and constant as possible.
Conductor resistance
(Resistance load per length unit R')		 The resistance load per length unit measures the loss in metallic conductors. The conductor dimensions, the conductive materials and the temperature determine the DC-resistance Ro'. Because of the skin-effect, the resistance load per length increases with increasing frequency. It also increases with increasing cable length. 
Decibel [dB]
 In engeneering, the relationship between received voltage (V2) and transmitted voltage (V1) is expressed in[dB]. The relationship is:
 V2/V1 [dB] = 20 10log (V2/V1).
V2/V1
[dB]		 Incoming signal in % V2/V1
[dB]		 Outgoing signal in %
0 100 4.0 63
0.1 98,8 20 10
0.2 97,7 40 1
0.9 90,1 60 0,1
1 89,3 80 0,01
2 79,4 100 0,001
EMC
(Electromagnetic compatibility)		 The ability of electrical equipment to satisfactorily function in its electromagnetic environment and also not to inadmissably influence the same environment occupied by other equipment.
FRNC, FR /LSOH or FRNC/LSOH FR means flame-retardant
NC means non-corrosive effects
LS means low smoke development
OH, 0H and ZH means non-halogen, zero-halogen or halogen-free.
Impedance Zo
(Characteristic Impedance)
 The impedance of a line depicts the relationship of the advancing voltage wave to a current wave advancing in the same direction. Common values are 100, 120 and 150 Ohms. Important is that the impedance of the cable matches the input/output impedance of the connecting device.
Mutual capacitance
 Mutual capacitance is a function of the line geometry (conductor<>conductor<>screen) and the dielectric constand (DC) of the isolation.
As long as the DC of the isolation remains constant with frequency, the capacitance per length unit almost frequency independent. Mutual capacitance increases linearly with the cable length.
Mutual inductance
(Inductance per length unit L')
 Inductance per length unit consists of several components. External inductivity is determined by the line geometry and the magnetic material properties. It is independent of frequency.
Since predominantly non ferromagnetic metals are used as conductors,it is also independent of current.
The internal inductivity can be traced back to the current and the associated magnetic field. Because of the current displacement, this part disappears at high frequencies.
In addition, for screened, symmetrical lines, the frequency-dependent cladding inductivty as well as inductivity inducted by short range effects must be taken into account.
Next, Fext
(Crosstalk attenuation)		 In cables with multiple pairs, their field effect of the signal transmission of a pair induces an interfering signal in neighbouring pairs.
The crosstalk is independent of the length and increases with increasing frequency. The difference between the desired signal and that measurable interfering signal on the neightbouring pairs is referred to as crosstalk attenuation and is specified in dB. 
We differentiate between NEXT/Near End Cross Talk and FEXT/Far end Cross Talk
Non halogen

 

 Non-halogen plastics include PE (polyethylene), PP (polypropylene) and PUR (polyurethane). They are made flame-retardant with low smoke emission through the addition of additives. Non-halogen does not automatically mean that the cable is flame-resistant (refer to PE (polyethelyene) following.
nvp
(nominal phase velocity of propagation)
 nvp is the reciprocal of the propagation time of the phase of a sinusoidal wave relative the speed of light. It is specified as %c, where c is the speed of light. It is mainly determined by the relative permittivity of the dielectric.
PE (polyetylene) Polyethylene is a non-halogen plastic which burns easily. Additives can make PE flame-retardant with low smoke emission.
Propagation constant per lenght unit
 Each homogeneous line is completely characterised by four primary qualities related to line length. These are, in general, frequency-independent. They are:
resistance load per length R' (conductor resistance) in ohms 
inductance per length unit L'( mutual inductor) in henrys
capacitance per length unit C' (mutal capacitance) in farads
conductance per length unit G' in siemens.
PVC (polyvinylchloride)
 In contrast to polyethylene, polyvinylchloride contains halogens.
The halogens are chlorine, bromine, fluorine, iodine and astatine. Chlorine and fluorine are used to make plastic flame retardant and more resistant to outside influences.
PVC-sheathed cabels are flame-resistent.
Halogen-containing plastics generate highly poisonous gases when burned. These gases form aggressive acids when they dissove in water and are capable of causing extensive corrosion damage.
Relative permittivity (RP) This is the material constant of dielectric. 
The dielectric constant specifies how many times larger the capacitance of the capacitor would be if, instead of air, insulating material is used as the dielectric. 
If the RP of the empty space is multilied by the dielectric constant, the result is the RP of the dielectric.
Return Loss (RL) Owing to unavoidable manufacturing tolerances (measuring tolerances, different relative permittivities along the isolation), line parameters do not exhibit identical values at all locations along the line.
These irregulations in line structure, be they even very small, lead to reflections of volatage and current waves. The result:
Reflection factor Ratio of transmitted and reflected voltage and current waves at the irregulation
Return loss factor Sum of all the effective reflections on the line (decisive for line usability)
Return loss  Logarithm of the reciprocal of the return loss factor
Skin effect 

The higher the frequency of the desired or interfering signal, the more the high frequency current is forced to the outer surface of the conductor.    
Transfer impedance Transfer impedance is the decisive variable for the quality of screening and frequency dependence. It is the ratio of the voltage drop along a screen on the interfered side (outside) to the interfering current on the other side (inside) of the screen.
Transfer impedance is determined by the design of the screen, the skin effect and the capacitive coupling.
Unbalance to ground
 The unequalness of electrical properties of individual wires of a pair relative to ground or to a screen. It is the difference between the capacitance of conductor a <-> screen and the capacitance of conductor b <-> screen. It influences the transmission properties of the cable.
 
26.11.2002