|
Table 9.3 - Some data cabling
terms explained
|
| Attenuation |
A reduction in power
or amplitude of the transmitted signal. In cables, usually
expressed in decibels per unit length. |
| Attenuation to crosstalk
ratio (ATR ) |
The difference between
attenuation and crosstalk measured in decibels. |
| Backbone
cabling |
Cable and
connecting hardware that comprise the main and intermediate
cross-connections (often known as ”cross-connects“). |
| Bridged tap |
The multiple appearances
of the same cable pair or fibre at several distribution
points. |
| Channel |
The end-to-end transmission
path connecting any two points to which equipment is
connected. |
| Cross-connection |
A connection scheme between
cabling runs, subsystems and equipment using patch cords
or jumpers that attach to connecting hardware at each
end. |
| Crosstalk |
Noise or interference
caused by electromagnetic coupling from one signal path
to another and usually expressed in decibels. |
| Decibel (dB) |
A standard unit to express
transmission gain or loss as derived from a ratio of
signal amplitudes or power (see Table 9.13). |
| Equal level far-end cross-talk
(ELFEXT) |
Crosstalk measured at
the opposite end from which the disturbing signal is
transmitted normalised by the attenuation contribution
of the cable or cabling. |
| Far-end crosstalk (FEXT) |
Crosstalk measured at
the opposite end from which the disturbing signal is
transmitted. |
| Fibre optic transmission |
A communications system
where electrical data are converted to light energy
and transmitted through optical fibres. |
| Horizontal cross-connect
(HC) |
A cross-connect of horizontal
cabling to other cabling, such as horizontal, backbone
or equipment. |
| Hybrid cable |
An assembly of two or
more cables, of the same or of different types or categories,
covered by one overall sheath. |
| Jumper wire |
An assembly of twisted-pairs
without connectors on either end used to join telecommunications
links at a cross-connect. |
Near-end crosstalk
(NEXT) |
Cross-talk measured at
the end from which the disturbing signal is transmitted. |
| Patch cord |
A length of cable with
connectors on one or both ends used to join telecommunications
links at a cross-connect. |
| Private branch exchange
(PBX) |
A private switching system
usually serving an organisation, such as a business,
located on the customer’s premises. |
| Propagation delay |
The amount of time that
passes between when a signal is transmitted and when
it is received at the opposite end of the cable or cabling |
| Punch down |
A method of securing
wire to a quick clip, in which the insulated wire is
placed in the terminal groove and pushed down with a
special tool. As the wire is seated, the terminal displaces
the wire insulation to make an electrical connection.
|
| Quick clip |
An electrical contact
used to provide an insulation displacement connection
to telecommunications cables. |
| Ring conductor |
The unearthed (ungrounded)
conductor of the two in a cable pair. |
| Screened twisted-pair
(ScTP) |
A balanced twisted-pair
cable surrounded by metallic braid, foil, or both, and
bound in a single cable sheath. |
Shielded twisted-pair
(STP-A) |
A cable surrounded by
a metallic braid, foil, or both, and bound in a single
plastic sheath containing balanced twisted-pair conductors
that are individually sheathed. |
| Tip conductor |
The earthed (grounded)
conductor of the two in a cable pair. |
| Unshielded twisted-pair
(UTP) |
A cable with multiple
pairs of twisted insulated copper conductors bound
in a single sheath. |
| Webbed conductors |
The manufacturing
process that physically binds the conductor insulation
of the wire pairs of an unshielded twisted-pair cable. |