Since our site is about Wi-Fi routers, and other network equipment, I just had to prepare an article about twisted pair - a cable that connects network equipment to each other. Through which computers and other devices are connected to routers and modems. And also, a cable called twisted pair, most likely you have the Internet connected from the provider's equipment to your router, or directly to your computer. Also, almost all manufacturers of routers put a short network cable with their devices. It is needed to connect various devices to the router (PC, laptop, TV, game console, etc.).
In the modern world, data transmission technologies are developing at a truly high pace. It is quite possible to say “at the speed of light”, because you will not surprise anyone with the transmission of information streams using optical fiber. But with all the positive functional characteristics of such communication cables, they have several serious disadvantages. High cost and fragility are the key ones.
At the moment, you need to try very hard to find a person who has absolutely no idea what the Internet is or has never used it. A huge number of people have a personal computer at home with access to the World Wide Web. But in order to "bring" the Internet to your home PC, you must use a convenient, reliable, and most importantly strong cable. This is where the cable has come to the rescue for many years, which has received an incomprehensible, at first glance, name - twisted pair.
What is Twisted Pair?
Twisted pair is a special kind of network cable. It is based on one or more pairs of insulated as well as twisted conductors (the category of the cable depends on their number). The number of turns per unit of length is minimal, but sufficient to significantly reduce the mutual guidance during signal transmission. The top of the twisted pair is usually covered with a protective plastic sheath.
Recently, this type of communication cable has become the most common in the creation of local and structured cable networks. This was due to its low cost and ease of installation.
The main disadvantage of a twisted pair is a significant signal attenuation (up to the level of unrecognizability) at distances over 100 meters. But this disadvantage is easily eliminated with the help of repeaters.
Kinds
Depending on whether there is protection or not, as well as its quality, there are several types of cables created using this technology:
- unshielded twisted pair (UTP) - no additional protective devices are used;
- shielded twisted pair (STP) - copper mesh is used;
- foil twisted pair (FTP) - aluminum foil is used;
- Shielded Foil Twisted Pair (SFTP) - Uses copper mesh and aluminum foil.
However, in some types of shielded cable, protection around each pair can be used. This type of shielding provides significantly better protection against various kinds of guidance, both internal and external.
Twisted pair cable categories
There are currently about 15 categories of twisted pair cables. They are numbered from CAT 1 to CAT 8.2. In most cases, the category has a direct dependence on the number of pairs used to transfer information, as well as on the number of turns that are used per unit of length. Cable categories are clearly defined in the American Commercial Wiring Standard.
Let's briefly describe each of the categories:
- CAT 1 is a well-known telephone cable. It uses only one pair. Only applicable for voice transmission and making connections using a modem.
- CAT 2 is an obsolete cable type consisting of 2 pairs of conductors. It supported data transfer at speeds less than 4 Mbps. It was often used in token ring networks. Now rarely used in some telephone networks.
- CAT 3 is an improved version of the previous 2-pair cable. Designed to provide data transmission at speeds up to 10 Mbit / s. Now very often continues to meet in telephone networks.
- CAT 4 is another type of cable that is not used today. Consists of 4 pairs, has a transmission speed of up to 16 Mbit / s.
- CAT 5 - it is the cables of this category that are most often called "twisted pair" in the classical sense. Consists of 4 pairs. Transfer rates range from 100 Mbps (2 pairs are used) to 1000 Mbps (4 pairs are used).
- CAT 5e is an improved version of the usual 5th category. Also consists of 4 pairs. The cable has the same speed characteristics as the twisted pair of the previous category. Now this category is the most common.
- CAT 6 - 4 pairs are used for transmission, which allow to increase the transmission speed up to 10,000 Mbps.
- CAT 6a - 4 pairs are used for transmission, which allow increasing the transmission speed up to 10 Gbit / s.
- CAT 7 - 4 pairs are used for transmission, which allow to increase the transmission speed up to 10 Gbps. Cable in this category must be shielded.
- CAT 8 - is currently under development. Presumably, it will allow transmitting an information stream at a speed of up to 40 Gbit / s. Must have a common screen or screen for each pair.
The number of pairs in one cable can be up to 100 pieces! See how the different views (UTP, F / UTP, S / FTP, SF / UTP, U / FTP) and categories (Cat.3 to Cat.7A) might look in the LAN-ART telecommunications directory.
There are also published photos of the coils on which the wire is wound, you can find out the price and characteristics of the goods.
Methods and schemes for crimping twisted pair
Obviously, in order to connect a cable to various computer equipment or to switches and routers, the twisted pair must be terminated with convenient and standardized connectors. This type of communication cable uses an RJ-45 connector (the correct name is 8P8C, but we will use the familiar one).
In order for a twisted-pair network to work correctly, it is necessary to connect the contacts in the RJ-45 connectors in the appropriate order. This must be done, both from one and the other end of the cable. For ease of crimping, all wires are marked with standardized colors. Naturally, if you have sufficient knowledge, you can crimp a cable at your own discretion, but in order to avoid confusion when combining networks, it is better to use standard crimping schemes. There are only two of them: direct crimping order and cross crimping order (crossed).
- The first crimp scheme (direct) is used when connecting different types of equipment, for example, a laptop network card and a switch.
- The second crimping scheme (cross, or cross) is used when connecting the same type of equipment, for example, two laptops (sometimes to connect a computer with some old types of switches and hubs).
For crimping the cable, a special device is used - a crimper (tongs). I wrote about this in the article: how to compress a twisted pair cable into RJ-45? DIY network cable.
And now directly about the crimping procedure. Consider the category 5 twisted pair crimping circuits, as the most common at the moment.
Straight cable crimping scheme
This cable is the most common. It is suitable for connecting computers, laptops, TVs, etc., to routers and other network devices.
- The first option (type T586A): one side has the following order of contacts (from 1 to 8) - white-green, green, white-orange, blue, white-blue, orange, white-brown, brown. The other party has the same contact order. It is best to use this option.
- The second option (type T568B). One side has the following order of contacts (from 1 to 8) - white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. The other party has the same contact order.
Cross cable: crimp circuit
- One side has the following order of contacts (from 1 to 8) - white-green, green, white-orange, blue, white-blue, orange, white-brown, brown.
- The other side has the following order of contacts (from 1 to 8) - white-orange, orange, white-green, blue, white-blue, green, white-brown, brown.
To manufacture a gigabit crossover cable (with support for speeds up to 1 Gbps), you need to use a slightly different scheme:
- One end of the cable: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown.
- The other end of the cable: white-green, green, white-orange, white-brown, brown, orange, blue, white-blue.
The development of data transmission technologies does not stand still. It is theoretically possible that twisted pair will soon become an obsolete type of cable, but at the moment it is the most used, reliable and cheapest type of network cable.
