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| maximum_current = | data_signal = Packet data, defined by specifications | data_bit_width = One bit | data_bandwidth = 1.5, 12, 480, 5,000, 10,000 Mbit/s (depending on mode) | data_devices = 127 | data_style = Serial | cable = Four wires plus shield (pre-3.0); nine wires plus shield (USB 3.0) | physical_connector = Unique | num_pins = | pinout_col1_name = | pinout_col2_name = | pinout_image = frameless | pinout_caption = The standard-A USB plug (left) and standard-B plug (right) | pin1 = VCC (+5 V, red wire) | pin1_name = | pin2 = Data− (white wire) | pin2_name = | pin3 = Data+ (green wire) | pin3_name = | pin4 = Ground (black wire) | pin4_name = | pinout_notes = }} USB, short for Universal Serial Bus, is an industry standard developed in the mid-1990s that defines the cables, connectors and communications protocols used in a bus for connection, communication, and power supply between computers and electronic devices. It is currently developed by the USB Implementers Forum. USB was designed to standardize the connection of computer peripherals (including keyboards, pointing devices, digital cameras, printers, portable media players, disk drives and network adapters) to personal computers, both to communicate and to supply electric power. It has become commonplace on other devices, such as smartphones, PDAs and video game consoles. USB has effectively replaced a variety of earlier interfaces, such as serial and parallel ports, as well as separate power chargers for portable devices. == Overview == In general, there are three basic kinds or sizes related to the USB connectors and types of established connection: the older "standard" size, in its USB 1.1, 2.0, and 3.0 variants (for example, on USB flash drives), the "mini" size (primarily for the B connector end, such as on many cameras), and the "micro" size, in its USB 1.1, 2.0, and 3.0 variants (for example, on most modern mobile phones). Unlike other data cables (e.g. Ethernet, HDMI), each end of a USB cable uses a different kind of connector; a Type-A or a Type-B. This kind of design was chosen to prevent electrical overloads and damaged equipment, as only the Type-A socket provides power. There are cables with Type-A connectors on both ends, but they should be used carefully.〔(【引用サイトリンク】url=http://www.cablestogo.com/learning/connector-guides/usb )〕 Therefore, in general, each of the different "sizes" requires four different connectors; USB cables have the Type-A and Type-B plugs, and the corresponding receptacles are on the computer or electronic device. In common practice, the Type-A connector is usually the full size, and the Type-B side can vary as needed. The mini and micro sizes also allow for a reversible Type-AB receptacle, which accepts either a Type-A or a Type-B plug. In this scheme, known as ''USB On-The-Go'', one receptacle performs double duty in space-constrained applications. Counter-intuitively, the "micro" size is the most durable from the point of designed insertion lifetime. The standard and mini connectors were designed for less than daily connections, with a design lifetime of 1,500 insertion-removal cycles. (Improved mini-B connectors have reached 5,000-cycle lifetimes.) Micro connectors were designed with frequent charging of portable devices in mind; not only is design lifetime of the connector improved to 10,000 cycles,〔 but it was also redesigned to place the flexible contacts, which wear out sooner, on the easily replaced cable, while the more durable rigid contacts are located in the micro-USB receptacles. Likewise, the springy part of the retention mechanism (parts that provide required gripping force) were also moved into plugs on the cable side. USB connections also come in five data transfer modes, in ascending order: Low Speed, Full Speed, High Speed (2.0), SuperSpeed (3.0), and SuperSpeed+ (3.1). High Speed is supported only by specifically designed USB 2.0 High Speed interfaces (that is, USB 2.0 controllers without the High Speed designation do not support it), as well as by USB 3.0 and newer interfaces. SuperSpeed is supported only by USB 3.0 and newer interfaces, and requires a connector and cable with extra pins and wires, usually distinguishable by the blue inserts in connectors. 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「USB」の詳細全文を読む スポンサード リンク
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