Already with the advent of the first computers, there was a need for a convenient and fast way to exchange digital data between them. Perforated sheets, magnetic tapes and disks (first flexible and then hard), optical storage media, although partially solved the problem, but their use had one significant drawback - it was necessary to somehow deliver the media with data to the target computer, therefore, " convenience ”was very conditional.
It is not surprising that in the eighties it became possible to transfer information between digital devices through the organization of a network connection between them (Ethernet). A special adapter (network card) was installed in each computer , into which a connecting coaxial cable was connected. This made it possible to transfer data directly, according to the Ethernet 10BASE2 standard (other varieties are less known and are not widely used). However, the standard required that the wave impedance of the cable be 50 Ohms, making it difficult to eliminate possible damage.
With the advent of a more modern, fast Ethernet, supporting a transmission speed of up to 100 megabits, the coaxial cable has been replaced by twisted pair. In addition to lowering the cost, if any of the cores was broken, you could simply twist it and restore the segment's performance. What is twisted pair? These are several pairs of conductors isolated from each other, twisted in pairs and assembled in a single shell. The conductor of wires can be either solid or consisting of thin copper hairs. The first option is the trunk, usually used for laying in the walls to distribution sockets. The plexus pitch of each pair is different, which reduces interference. The wires are distinguished by the color of the insulation, so there is no need to “ring”.
Sometimes the question arises of what a patch cord is. This is a connecting cable with connectors at the ends. Usually, the length is limited to 5 m, although this restriction is removed in the TSB-75 office standard. If you want to connect two computers to each other, then the patch cord can be purchased at any computer store.
By the way, as a rule, this is a twisted pair cable. Moreover, the buyer does not need to think about how to compress the twisted pair, because the connectors are already connected in a certain way (usually PC-PC, cross-connection or “crossover”). Note that many modern devices automatically determine the type of connection and adapt to it. However, sometimes you have to independently understand how to compress a twisted pair. For example, with self- installation of a local network.
In this case, you have to read the relevant forums and specifications. By the way, there is nothing complicated in how to compress a twisted pair - a little care and accuracy are enough.
You can purchase special crimping pliers, their price is quite affordable. Although, with proper skill, everything can be done even with nails.
So how to compress a twisted pair? You will need the cable itself (for a twisted pair of category 5 at 100 Mbps, the maximum distance is about 130 m) and two RJ-45 connectors. We trim the edges of the cable, aligning it and cutting off possible damage. Remove the outer layer of insulation. The length of this section depends on the type of connector: the latter should fix part of the shell, and not hang on the same conductors. Unwrap the pairs and align them (they should protrude 1 cm). In accordance with the scheme (see below), insert the cores into the connector. With the help of ticks, we connect the veins with it.
There are two crimping methods - T568A (Siemon) and T568B (AT&T). The second variety is used more often. In the first, the signals are transmitted in pairs of "white-green" and "white-orange", as well as orange and green wires. In the second, these are “white-orange” and “green-white” pairs, as well as white and green.
To connect different devices (hub-PC), the same connection method is used on both sides. If you need to connect two computers or two hubs, then on the one hand the cable is routed according to T568A, and on the other - according to T568V. Visual wiring diagrams can be easily found on the corresponding resources on the Web.
Tip for the "lazy": to create the simplest network of two PCs, you can buy a ready-made patch cord and a twisted pair cable of the desired length. Cut the patch cord in the middle, strip the ends of the conductors on it and the main cable, twist (solder) the cores in accordance with the color coding. Insulate. This solution works successfully at distances up to 140 m.