Specifications

2009
2010
31
FURTHER INFORMATION
▼ NEXT- Near end crosstalk;
The energy of an electrical sig-
nal induced by a disturbing cir-
cuit in a disturbed circuit, meas-
ured on the disturbed circuit at
the same end as the disturbing
source. In practice one meas-
ures near end crosstalk attenu-
ation, in other words, to what
extent the disturbing signal in-
duced on the disturbed circuit is
attenuated by the line. Ex-
pressed in dB.
▼ FEXT- Far end crosstalk;
The energy of an electrical signal induced by a disturbing circuit in a disturbed circuit, measured
on the disturbed circuit at the opposite end from the disturbing source. In practice one meas-
ures far end crosstalk
attenuation, in other
words, to what ex-
tent the disturbing
signal induced on the
disturbed circuit is at-
tenuated by the line.
Expressed in dB.
▼ ACR- Attenuation to Crosstalk Ratio;
The difference between the atten-
uation (IL) and near end crosstalk
(NEXT). Expressed in dB at a giv-
en frequency. This is a quality crit-
ical parameter, inasmuch as it en-
sures that the signal transmitted
on a pair is stronger in reception
than the sum of crosstalk from ad-
jacent pairs.
PAIR TO PAIR AND POWER SUM
MEASUREMENT
▼ WM- Wiremap;
Established standards prescribe two different types of connection depending on the reference
standard, which invert the positions of the White/Orange pair with that of the White/Green
pair. Furthermore, the wiremap should preferably be made available with a software which can
be used by the administrator to manage the process of evolution.
▼ LP- Loop resistance;
The DC resistance of the copper conductor of the circuit composed of wires "a" and "b" of the
pair in question. Expressed in W/m. For the measurement to be precise, the resistance of the
short circuit at the far end should be negligible. Otherwise, one can only distinguish a low re-
sistance short circuit (<1000W) from a high resistance one.
▼ IL- Insertion loss;
Reduction of ampli-
tude of an electrical
or optical signal prop-
agated in a transmis-
sive medium (copper
pair or optical fibre).
Expressed in dB/m or
dB/km, in which case one speaks of specific attenuation.
▼ RL- Return loss;
The ratio of the transmitted to the reflected signal measured at the line input. Expressed in dB.
In practice, this is the attenuation suffered by the reflection of an electrical signal which occurs
at the points of impedance mismatch of a copper conductor. The RL of an optical fibre is anal-
ogous but the concept of reflection is different, inasmuch as it consists in the energy reflected
when the light is transmitted in a reflective medium.
TRANSMISSIVE PARAMETERS
The electrical parameters of a cable are essentially determined by its mechanical parameters. The relation between them cannot, however, be reduced to simple for-
mulae, especially at high frequencies, where electromagnetic phenomena must be considered in addition to purely electrical ones. The following parameters apply
to screened/unscreened cable connections and are basic measures, in other words, the cable’s dataplate data.
• WM Wiremap;
• LP Loop resistance;
• IL Insertion Loss;
• RL Return Loss;
• NEXT Near End Crosstalk;
• FEXT Far End Crosstalk;
• ACR Attenuation to Crosstalk Ratio;
• PSN Power Sum Next;
• PSACR Power Sum Attenuation to Crosstalk Ratio;
• ELFECT Equal Level Far End Crosstalk;
• PSELFECT Power Sum Equal Level Far End Crosstalk;
• AXT Alien Cross Talk;
• PD Propagation Delay;
• DS Delay Skew.