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Ethernet cables or networks cables are used for data transmission between devices on a network. They consist of a copper cable with 4 pairs of wires and connected by RJ45 connectors on each end of the cable. Most Ethernet cables in use today are either Cat5e and Cat6 which offer higher data transfer rates than the older types such as Cat5 and Cat4. Although various types of Ethernet cables look the same, the internal wiring distinguishes. Ethernet cables can come in two different wiring applications: straight-through and crossover, each of them with different wire arrangement in the cable for serving different purposes.


Straight-Through Ethernet Cables

Straight-through cable is the most common type and is used to connect different type of devices. This type of cable is easy to find in stores and can be used to:

1)Connect a computer to a switch/hub's normal port.

2)Connect a computer to a cable/DSL modem's LAN port.

3) Connect a router's WAN port to a cable/DSL modem's LAN port.

4) Connect a router's LAN port to a switch/hub's uplink port. (normally used for expanding network)

5) Connect 2 switches/hubs with one of the switch/hub using an uplink port and the other one using normal port.


If you need to check how straight-through cable looks like, it's easy. Both side (side A and side B) of cable have wire arrangement with same color. For example, Cat5e UTP cable usually uses only four wires when sending and receiving information on the network. The four wires, which are used, are wires 1, 2, 3, and 6. When you configure the wire for the same pin at either end of the cable, this is known as a straight-through cable.

Straight-Through Ethernet Cables

Crossover Ethernet Cables

Crossover cables are usually used to connect the same type of devices and may be a little harder to find since they aren’t used nearly as much as straight-through cables. A crossover cable can be used to:

1) Connect 2 computers directly.

2) Connect a router's LAN port to a switch/hub's normal port. (normally used for expanding network).

3) Connect 2 switches/hubs by using normal port in both switches/hubs.


Compared with straight-through Ethernet cables, the internal wiring of crossover cables reverses the transmit and receive signals. That is to say, the two end of the crossover Ethernet cable are wired differently. And the reversed color-coded wires can be seen through the RJ-45 connectors at each end of the cable.


Crossover Ethernet Cables

Identifying Straight-Through and Crossover Cables

Whether they are straight-through or crossover cables, all Ethernet cables essentially look the same. When dealing with the inevitable pile of unlabeled cables that forms in every home, this can make dealing with them tricky. Fortunately, you can quickly identify crossover and straight cables if you know what to look for.


When determining if an Ethernet cable is a straight or crossover cable, examine the connectors. Observe the pin configuration carefully. The pins are color coded, so you should have no trouble doing this. If the pins are configured in the same way, you are looking at a straight cable. If not, it is a crossover cable.



Nowadays, the need for crossover cables has been eliminated with more modern equipment. Gigabit Ethernet was created with a widely used option called Auto-MDIX (automatic medium-dependent interface crossover). This technology detects whether you need a crossover cable or a straight-through cable, and it automatically configures the network interface card accordingly, which means that crossover function would be enabled automatically when it's needed.

Copper cabling has been in use since electricity was invented and its quality has continued to improve. Network managers pick copper cabling for various reasons. For instance, copper cables, especially UTP cables, are as inexpensive as optical fibers and easy to install. Moreover, the installation methods are well understood, and the components (patch panels, wall-plate outlets, connecting blocks, etc.) are inexpensive. This article will provide guidelines for copper cabling installation.

Standards to Follow

One of the most important elements to plan and deploy a telecommunication infrastructure is to make sure you are following the ANSI/TIA-568-C standard. This standard will ensure that your cabling system is interoperable with any networking or voice applications that have been designed to work with that standard.

Cable Distances

ANSI/TIA-568-C standard defines the maximum distance that a horizontal cable should traverse. The tips relating to distance and the installation of copper cabling include following:

  • Never exceed the 90-meter maximum distance for horizontal cables.
  • Horizontal cable rarely goes in a straight line from the patch panel to the wall plate. Don’t forget to account for the fact that horizontal cable may be routed up through walls, around corners, and through conduit.
  • Account for any additional cable distance that may be required as a result of trays, hooks, and cable management.
  • Leave some slack in the ceiling above the wiring rack in case re-termination is required or the patch panel must be moved. Some professional cable installers leave the extra cable loop in the ceiling bundled together or looped around a hook, shown as below.

J hook

Wiring Patterns

The ANSI/TIA-568-C standard introduces two wiring patterns for modular jacks and plugs: T568-A and T568-B. The only difference between these wiring patterns is that pin assignments for pairs 2 and 3 are reversed. The wiring pattern chosen makes no difference to the applications used. They both work the same way. The most important factor is to choose one wiring configuration and stick with it. If you use T568-A at one end, you must use it at the other; likewise with T568-B.The cable pairs are assigned to specific pin numbers. The pins are numbered from left to right if you are looking into the modular jack outlet or down on the top of the modular plug. The following picture shows the pin numbers for the eight-position modular jack (RJ-45) and plug


Considerations Before Installing

When planning a cabling infrastructure that includes copper cabling, ask yourself some questions before taking action. For example, how many cables should be run to each location? Should you use cable trays, J hooks, or conduit where the cable is in the ceiling space? Or is there a danger of cable damage from water, rodents, or chemicals? Consider any area that cable may be run through and take into account what you may need to do to protect the cable.Good cable management starts with the design of the cabling infrastructure. When installing horizontal cable, consider using cable trays or J hooks in the ceiling to run the cable. They will prevent the cable from resting on ceiling tiles, power conduits, or air-conditioning ducts. Furthermore, make sure that you plan to purchase and install cable management guides and equipment near patch panels and on racks so that when patch cables are installed, cable management will be available.


Installing Copper Cables

When you start installing copper cabling, much can go wrong. Even if you have adequately planned your installation, situations can still arise that will cause you problems either immediately or in the long term. Here are some tips to keep in mind for installing copper cabling.

  • Do not untwist the twisted pairs at the cable connector or anywhere along the cable length any more than necessary.
  • Bridged taps are not allowed.
  • Use connectors, patch panels, and wall plates that are compatible with the cable.
  • Never splice a data cable if it has a problem at some point through its length; run a new cable instead.
  • When terminating, remove as little of the cable’s jacket as possible, preferably less than three inches. When finally terminated, the jacket should be as close as possible to where the conductors are punched down.
  • Don’t lay data cables directly across ceiling tiles or grids. Use a cable tray, J hook, horizontal ladder, or other method to support the cables. Avoid any sort of cable-suspension device that appears as if it will crush the cables.
  • If you have a cable with damaged pairs, replace it. Don’t use another unused pair from the same cable because other pairs may be damaged to the point where they only cause intermittent problems, which are difficult to solve. Substituting pairs also prevents any future upgrades that require the use of all four pairs in the cable.

Besides the tips above, you should also separate voice and data patch panels. Some installations of voice and data cabling will terminate the cabling on the same patch panel. Although this is not entirely frowned upon by cabling professionals, many will tell you that it is more desirable to have a separate patch panel dedicated to voice applications. This is essential if you use a different category of cable for voice than for data (such as if you use Category 5e cable for data but Category 3 cable for voice).

patch panel

Take the picture above as an example, the wall plate has two eight-position modular outlets (one for voice and one for data). The outlets are labeled V1 for voice and D1 for data. In the telecommunications closet, these two cables terminate on different patch panels, but each cable goes to position 1 on the patch panel. This makes the cabling installation much easier to document and to understand.


Copper cabling installation is not as easy as thought. You should follow the ANSI/TIA-568-C standard to confirm the cable distance and wiring patterns. And before installation, you’d better ask yourself some questions that you may meet during cable installing. Moreover, take the tips mentioned above when you begin to install copper cables. Hope the information mentioned in this article would be useful for you when needed.


Source: Blog of FS.COM - Official Blog of Fiberstore (FS.COM)

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