Ethernet Cable Types & Pinout: cat 5, 5e, 6, etc

Various cables are used for carrying Ethernet: current common types include Cat 5, 5e, and Cat 6, and the RJ45 connector is widely used

Ethernet IEEE 802.3 Includes:
Ethernet introduction     Standards     Ethernet data frame structure     100 Base T     Gigabit Ethernet, 1GE     Cables     Power over Ethernet, PoE    

There are many Ethernet cables that can be bought. Often these cables are supplied free with equipment that uses Ethernet connectivity in some way or another.

There are several different varieties of Ethernet cable that can be obtained: speed variations, crossover cables, Cat 5, Cat 5e, Cat6, etc..

Normally Ethernet cables will be bought and there is no major need to understand what is inside or on the connectors, although it can be both interesting and helpful on some occasions. Even so, an understanding of the different types of Ethernet cable and the maximum lengths that should be used is helpful.

The commonly used cables: Cat 5, Cat 5e, Cat 6 all have different levels of performance, and therefore to is necessary to buy or select the right cable for the right application.

Ethernet Cable Summary

A summary of Ethernet cables and their maximum operating lengths is given below:

Ethernet Cable Type Summary
Specification Cable type Maximum length
10BaseT Unshielded Twisted Pair 100 metres
10Base2 Thin coaxial cable 180 metres
10Base5 Thick coaxial cable 500 metres
10BaseF Fibre optic cable 2000 metres
100BaseT Unshielded twisted pair 100 metres
100BaseTX Unshielded twisted pair 220 metres

Lengths provided are those accepted as the maximum.
These lengths are not necessarily included in the IEEE standard.

Categories for Ethernet cables

A variety of different cables are available for Ethernet and other telecommunications and networking applications. These 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 sued 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. It is the 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.
  • Cat-5e:     This form of cable is recognised by the TIA/EIA and is defined in TIA/EIA-568-B.. It has a slightly higher frequency specification that Cat-5 cable as the performance extends up to 125 Mbps. It can be used for 100Base-T and 1000Base-t (Gigabit Ethernet).
  • Cat-6:     This cable is defined in TIA/EIA-568-B. It provides more than double the performance of Cat-5 and Cat-5e cables allowing data at up to 250Mbps to be passed.
  • 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.

Further descriptions of Cat-5 and Cat-5e cables are given below as these are widely used for Ethernet networking applications today.

Ethernet Cat 5 cable & pinout

Cat 5 cables or to give them their full name category 5 cable is the current preferred cable type for LAN network and telephone wiring where twisted pair cabling is required. Cat 5 cables consist of an unshielded cable comprising four twisted pairs, typically of 24 gauge wire. The terminating connector is an RJ-45 jack. In view of this these Cat5 network cables are often referred to as RJ45 network cables or RJ45 patch cables. Certified Cat-5 cables will have the wording "Cat-5" written on the side. As they conform to EIA/TIA 568A-5, this is written on the outer sheath. It is always best to use the appropriate network cables when setting up a network as faulty or not to standard cables can cause problems that may be difficult to identify and trace.

Cat5 network cable is now the standard form of twisted pair cable and supersedes Cat 3. The Cat 5 cables can be used for data speeds up to 125 Mbps, thereby enabling them to support 100Base-T which has a maximum data speed of 100 Mbps whereas the Cat-3 cable was designed to be compatible with 10Base-T. The Cat5 cable is able to support working up to lengths of 100 metres at the full data rate.

Where it is necessary to operate at higher speeds, as in the case of Gigabit Ethernet, an enhanced version of Cat 5 cable known as Cat 5e is often recommended, although Cat 5 is specified to operate with Gigabit Ethernet, 1000Base-T. Alternatively Cat 5e can be used with 100Base-T to enable greater lengths (up to 350 metres) to be achieved.

The wires and connections within the Cat 5 or Cat 5e cable vary according to the applications. A summary of the signals carried and the relevant wires and connections is given in the table below:

Ethernet Cable Pinout & Details
Colour Telephone 10Base-T 100Base-T 1000Base-T PoE
Mode A
Mode B
1 White / green   +TX +TD +BI_DA 48 V out  
2 Green   -TX -TX -BI_DA 48 V out  
3 White / orange   +RX +RX +BI_DB 48 V return  
4 Blue Ring     +BI_DC   48 V out
5 Blue / white Tip     -BI_DC   48 V out
6 Orange   -RX -RX -BI_DB 48 V return  
7 White / brown       +BI_DD   48 V return
8 Brown       -BI_DD   48 V return

RJ-45 / Cat 5 / Cat 5e Pinout & Wiring

In the table, TX is transmitted data, and RX is received data. BI_Dn is bi-directional data, A, B, C, and D.

Ethernet Cat 5 crossover cables

There are a number of different configurations of cable that may be employed according to the equipment and the requirement. The most common type are the straight through cables which are wired in a 1 to 1 configuration. However Cat-5 crossover cables are also required on occasions.

Typically a Cat-5 cable used to connect a computer (PC) to a switch will be a straight through cable. However if two computers or two switches are connected together then a Cat5 crossover cable is used.

Many Ethernet interfaces in use today are able to detect the type of cable, whether it is a straight through or crossover cable, and they are able to adapt to the required format. This means that the requirement for Cat-5 crossover cables is less than it might otherwise be.

When using Cat-5 Ethernet crossover cables, they are not marked with the fact that they are crossover cables. Accordingly it is often wise to mark them to avoid confusion later.

Ethernet Cat 5e cables

In order to improve the performance of the cabling used for Ethernet and other applications, the Cat 5 cable was upgraded to cat 5e. This cable provides for improved levels of screening and reduced cross-talk. This is achieved by having individually screened twisted pairs.

A variety of different cables are seen connecting different Ethernet elements together. Cat5, Cat5e and Cat6 are all seen. The cables use the cost efficient but effective RJ45 patch connector and using this, these Ethernet cables are able to link or patch multiple items of Ethernet based equipment together. On some occasions where specialised connectivity is needed crossover cables may be required - these sold be clearly marked as such as they may get used elsewhere unknowingly and cause the connection not to work. Apart from this using Cat 5, Cat5e and Cat 6 Ethernet cables is very easy and there are normally very few issues.

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