Shielded Cables
 Often
network cables carry very high-speed data and voice transmission,
requiring good accuracy over short to medium distances.
When many cables collect behind equipment or travel
together under floor tiles or through cable trunking, other cables
will cause interference and interrupt the data flowing through it.
This type of interference is known as Electromagnetic Interference
(EMI).
Shielded Twisted-Pair (STP) cables use a thin
layer of foil wrapped between the twisted pairs and the outer sheath
to prevent excessive EMI from interfering with the data.
When the original STP specification was drawn
up by IBM in 1984, 150 ohm cable types 1, 2, 6, 8 and 9 supported
frequencies up to 16MHz. Later the STP-A (enhanced) IBM specification,
otherwise known as the TIA/EIA 568-A standard, was released to support
frequencies up to 300MHz which allowed a much higher speed of data
transfer.
The following table lists all the types of STP
cabling laid out by the IBM Cabling Standard.
| Type
1 |
Two
shielded twisted pairs, 22 AWG solid copper conductors.
Suitable for non-plenum data, plenum data, outdoor
data and riser. |
| Type
2 |
Two
shielded twisted pairs, 22 AWG solid copper conductors,
plus four voice grade twisted pairs, 22 AWG solid copper
conductors.
Suitable for non-plenum data, plenum data and voice. |
| Type
6 |
Two
shielded twisted pairs, 26 AWG solid copper conductors.
Suitable for patch panel cabling. |
| Type
8 |
Two
individually shielded twisted pairs, 26 AWG solid or
stranded copper conductors.
Suitable for under-carpet data. |
| Type
9 |
Two
shielded twisted pairs, 26 AWG solid or stranded copper
conductors.
Suitable for non-plenum data, plenum data and riser. |
| Type
1A |
Two
shielded twisted pairs, 22 AWG solid copper conductors.
Suitable for non-plenum data, plenum data and riser. |
| Type
2A |
Two
shielded twisted pairs, 22 AWG solid copper conductors,
plus four voice grade twisted pairs, 22 AWG solid copper
conductors.
Suitable for non-plenum data, plenum data and voice. |
| Type
6A |
Two
shielded twisted pairs, 26 AWG stranded copper conductors.
Suitable for patch panel cabling. |
| Type
9A |
Two
shielded twisted pairs, 26 AWG solid or stranded copper
copper conductors.
Suitable for non-plenum data, plenum data and riser. |
|
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