Категории для кабелей ethernet

A variety of different cables are available for Ethernet and other telecommunications and networking applications. These network cables that are described by their different categories, e.g. Cat 5 cables, Cat-6 cables, etc, which are often recognised by the TIA (telecommunications Industries Association) and they are summarised below:

• Cat-1: This is not recognised by the TIA/EIA. It is the form of wiring that is used for standard telephone (POTS) wiring, or for ISDN.
• Cat-2: This is not recognised by theTIA/EIA. It was the form of wiring that was used for 4Mbit/s token ring networks.
• Cat-3: This cable is defined in TIA/EIA-568-B. It is used for data networks employing frequencies up to 16 MHz. It was popular for use with 10 Mbps Ethernet networks (100Base-T), but has now been superseded by Cat-5 cable.
• Cat-4: This cable is not recognised by the TIA/EIA. However it can be used for networks carrying frequencies up to 20 MHz. It was often used on 16Mbps token ring networks.
• Cat-5: This is not recognised by the TIA/EIA. This is the network cable that is widely used for 100Base-T and 1000Base-T networks as it provides performance to allow data at 100 Mbps and slightly more (125 MHz for 1000Base-T) Ethernet. The Cat 5 cable superseded the Cat 3 version and for a number of years it became the standard for Ethernet cabling. Cat 5 cable is now obsolete and therefore it is not recommended for new installations.
  
  Cat 5 cable uses twisted pairs to prevent internal crosstalk, XT and also crosstalk to external wires, AXT.
  
  Although not standardised, the Cat 5 cable normally uses 1.5 - 2 twists per centimetre.
• Cat-5e: This form of cable is recognised by the TIA/EIA and is defined in TIA/EIA-568, being last revised in 2001. It has a slightly higher frequency specification that Cat-5 cable as the performance extends up to 125 Mbps.
  
  Cat-5e can be used for 100Base-T and 1000Base-t (Gigabit Ethernet). Cat 5e standard for Cat 5 enhanced and it is a form of Cat 5 cable manufactured to higher specifications although physically the same as Cat 5. It is tested to a higher specification to ensure it can perform at the higher data speeds. The twisted pairs within the network cables tend to have the same level of twisting as the Cat 5 cables.
• Cat-6: This cable is defined in TIA/EIA-568-B provides a significant improvement in performance over Cat5 and Cat 5e. During manufacture Cat 6 cables are more tightly wound than either Cat 5 or Cat 5e and they often have an outer foil or braided shielding. The shielding protects the twisted pairs of wires inside the Ethernet cable, helping to prevent crosstalk and noise interference. Cat-6 cables can technically support speeds up to 10 Gbps, but can only do so for up to 55 metres - even so this makes them relatively long Ethernet cables.
  
  The Cat 6 Ethernet cables generally have 2+ twists per cm and some may include a nylon spline to reduce crosstalk, although this is not actually required by the standard.
• Cat-6a: The “a” in Cat 6a stands for “Augmented” and the standard was revised in 2008. The Cat 6a cables are able to support twice the maximum bandwidth, and are capable of maintaining higher transmission speeds over longer network cable lengths. Cat 6a cables utilise shielded which is sufficient to all but eliminate crosstalk. However this makes them less flexible than Cat 6 cable.
• Cat-7: This is an informal number for ISO/IEC 11801 Class F cabling. It comprises four individually shielded pairs inside an overall shield. It is aimed at applications where transmission of frequencies up to 600 Mbps is required.
• Cat-8: Cat 8 cables have now been released and provide a huge step up in data rate / bandwidth. Accordingly these Cat 8 cables are geenrally more expensive than the older versions like Cat 6, or even Cat 7.