LAN Cable Transmission Medium
LAN Cable Transmission medium
Optical fiber is a promising medium for network transmission. But because the current price is expensive, small and medium-sized office LAN is not necessary to choose it. The main application of optical fiber is to use as trunk line in large LAN. But along with the cost reduction, in the near future, the fiber to the building, to the door, will even extend to the desktop, to give us a completely new high-speed experience.
Twisted-pair (Twisted Pair) are divided into block (Shielded Twisted Pair, the STP) and Unshielded (Unshielded Twisted Pair, UTP) two kinds.
The so-called shield refers to the outside of the internal signal line of the network wire is wrapped in a metal mesh, outside the shielding layer is the insulation outer skin, the shielding layer can effectively isolate the external electromagnetic signal interference.
UTP is one of the most frequently used networks in LAN. The wires are covered with eight signal lines in the plastic insulating sheath. They have eight colors. They are: white orange, orange, white green, blue, white blue, green, white brown and brown (568B sequence). Although there are eight lines, only four are actually useful. They are: white orange, orange, white green and green. Each of them is twined together, forming a total of four pairs, hence the name of the twisted pair.
The purpose of intertwining
The purpose of the twisted pair is to use the electromagnetic field generated by the current in the copper wire to counteract the interference of the neighboring lines and reduce the interference from the outside. Each pair of lines around each other in every inch length number determines the ability of anti-jamming and communication quality, winding, the more closely the higher the quality of communications, network can support higher data transfer rate, of course, the higher the cost of it is. International electrical and telecommunications commission, EIA/TIA? Electronic Industry Association/Telecommunication Industry Association has established international standards and according to the use of field of UTP cable is divided into five Categories (Categories or CAT), every Categories of cable manufacturers in the insulating sheath on the type, such as a CAT - 5 or Categories - 5, we need to pay attention to when the choose and buy.
Using the length
CAT - 3 and CAT - 5 is the most used type of computer network, without any increase in other network connection device (such as a hub), under the condition of single period of CAT - 3, the CAT - 5 maximum permissible use length is 100 meters, 100 base - TX enhanced network is less than 220 meters. The so-called super - five line, which is often said, is the CAT - 5 standard that the manufacturer has unilaterally raised to ensure the quality of communication, and has not been recognized by EIA/TIA.
RJ 45 crystal head -
UTP cable to use RJ - 45 crystal head to connect, RJ45 connector is a kind of fixed direction can only insert and automatically to prevent loss of plastic connectors, cables inside each root signal lines need to use special line pressing pliers make it closely connect with RJ - 45 contact, according to different network speed and standard network structure, the point of contact with the cable connection mode is also different.