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USB (Universal Serial Bus) is the current generation of computer peripherals most using transmission interface. The USB interface is initiated by Intel and Microsoft Corporation, its major character is supports Hot-Plug and Plug-n-Play. Users don't need to reset the computer and open chassis after installing the hardware. The operation is more convenient than penetrating the expansion of PCI and the ISA Bus.

In the past PC main output devices, such as the keyboard & mouse etc. which are the low speed equipments, and the scanner & monitor are low resolution, the serial port and parallel port may deal with fully. Since 1990 the quality of devices (resolution & data transmission speed etc.) and the quantity (devices quantity increase) are synchronized promotion cause the interface connection mode unable to meet the need. Therefore in 1994, Intel, Compaq, NEC, Digital, Northern, IBM, Microsoft etc. 7 companies has established USB-IF (USB Implementers Forum), that is the organization which as the name for the agreement of serial PC and devices' goal established, and in 1996 January 15 take Intel as the head, formulated the USB1.0 interface chipset's standard officially.

In 1998 the USB 1.1 transmission interfaces are promoted, and named the USB connection interface. In 2000 Intel published the USB2.0 official specification, at current market most computer peripherals support the USB transmission interface, as portable HD, printer, mouse etc.. USB1.1 & USB2.0 are difference in the transmission speed. USB2.0 (High-Speed) maximum transmission speed (480Mbps) is higher than USB1.1 (Full-Speed) transmission speed (12Mbps) around 40 times, but at the end of 2008, defined USB3.0 (Super-Speed) transmission bandwidth up to 5Gbps, is USB2.0 10 times, estimated in 2009 the four quarter relating products are going on the market.

The reason that the USB interface is widely promoted, the most important reason is the downward compatibility, newest USB3.0 also carried on this superiority, the USB3.0 connection is compatible in old-style USB2.0 and the USB1.1 installment, users can place the USB installment connects to the USB3.0 port, so might increase USB3.0 the popularization rapidly, in addition the USB3.0 transmission line increased a group of difference holding wire, and from original 4-PIN to 9-PIN, the power output increases 5V/900mA from 5V/500mA as well, enables 90% above the USB equipment to be used smoothly without to connect the extra power, in addition up to 5G transmission speed to cause USB3.0 interface even more powerful. In MAC field gradually reduces the attention of 1394 FireWire line, the USB3.0 specification will appear anticipated will lead to the next three years in the consumption electronic transmission medium.