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Category 5 cable, commonly referred to as cat 5, is a twisted pair cable for carrying signals. This type of cable is used in structured cabling for computer networks such as Ethernet. The cable standard provides performance of up to 100 MHz and is suitable for 10BASE-T, 100BASE-TX (Fast Ethernet), and 1000BASE-T (Gigabit Ethernet). Cat 5 is also used to carry other signals such as telephony and video. This cable is commonly connected using punch-down blocks and modular connectors. Most category 5 cables are unshielded, relying on the balanced line twisted pair design and differential signaling for noise rejection. Category 5 was superseded by the category 5e (enhanced) specification,〔(【引用サイトリンク】title=Voice and Data Cabling & Wiring Installations )〕 and later category 6 cable. |- | |- | |} == Cable standard == The specification for category 5 cable was defined in ANSI/TIA/EIA-568-A, with clarification in TSB-95.〔(【引用サイトリンク】title=Additional Transmission Performance Guidelines for 4-pair 100 v category 5 Cabling )〕 These documents specify performance characteristics and test requirements for frequencies up to 100 MHz. Cable types, connector types and cabling topologies are defined by TIA/EIA-568-B. Nearly always, 8P8C modular connectors (often referred to as RJ45 connectors) are used for connecting category 5 cable. The cable is terminated in either the T568A scheme or the T568B scheme. The two schemes work equally well and may be mixed in an installation so long as the same scheme is used on both ends of each cable. Each of the four pairs in a cat 5 cable has differing precise number of twists per meter to minimize crosstalk between the pairs. Although cable assemblies containing are common, category 5 is not limited to 4 pairs. Backbone applications involve using up to .〔As noted in ANSI/TIA/EIA-568-B-2 standard for backbone applications〕 This use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and crosstalk from other pairs. The cable is available in both stranded and solid conductor forms. The stranded form is more flexible and withstands more bending without breaking. Permanent wiring (for example, the wiring inside the wall that connects a wall socket to a central patch panel) is solid-core, while patch cables (for example, the movable cable that plugs into the wall socket on one end and a computer on the other) are stranded. The specific category of cable in use can be identified by the printing on the side of the cable.〔(【引用サイトリンク】title=Ethernet Cable Identification and Use )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「category 5 cable」の詳細全文を読む スポンサード リンク
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