The commonly used twisted pair cable is composed of 4 pairs of twisted pairs twisted counterclockwise at a certain density, with the outer layer wrapped in a metal layer or plastic rubber skin. The diameter of copper wire is 0.4mm to 1mm. The twisting direction is counterclockwise, with a twisting distance of 3.81cm-14cm, and the difference in twisting length between adjacent twisted pairs is about 1.27cm. The winding density and direction of twisted pair, as well as the insulation material, directly affect its characteristic impedance, attenuation, and near-end crosstalk. Twisted pair cables can be classified into shielded twisted pair cables and unshielded twisted pair cables based on whether they are wrapped with a metal layer or a plastic rubber outer layer. They can transmit both analog and digital signals. Unshielded twisted pair cable (UTP) is composed of multiple pairs of twisted pairs wrapped in a plastic rubber sheath. Unshielded twisted pair cables are made by precise production techniques, which are proportional to the lay distance of each pair of wires and their ability to resist electromagnetic radiation and interference, combined with filtering and pairing techniques. Adopting these technical measures can reduce electromagnetic interference between unshielded twisted pair cable pairs. UTP has the following characteristics because it has no shielding layer: a. It is easy to install; b. Smaller and space saving. Shielded twisted pair cable, like unshielded twisted pair cable, has a copper twisted pair core and a plastic rubber sheath. Just adding a metal layer inside the sheath layer. According to the increased number of metal shielding layers and the wrapping method of the metal shielding layer, it can be further divided into three types: metal foil twisted pair cable (FTP), shielded metal foil twisted pair cable (SFTP), and shielded twisted pair cable (STP). FTP is wrapped in aluminum foil on multiple twisted pairs. SFTP is a method of longitudinally wrapping multiple pairs of twisted pairs with aluminum foil, followed by adding a metal woven mesh STP. After each pair of twisted pairs is longitudinally wrapped with aluminum foil, the multiple pairs of twisted pairs with aluminum foil are then added with a metal woven mesh. Both unshielded twisted pair cables and shielded twisted pair cables have a pull rope used to tear open the cable protective sleeve. The shielded twisted pair cable also has a leaking wire, which can be connected to the grounding device to release the metal shielding charge and eliminate interference between the wires
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