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USB, or Universal Serial Bus, is a connectivity standard that enables computer peripherals to be connected to a computer without reconfiguring the system or opening the computer box to install interface cards. USB was introduced in 1995 and replaces the serial, parallel, mouse and keyboard ports. The host computer automatically recognizes the device and installs the appropriate drivers. It is a fast, bi-directional, low-cost, dynamically attachable serial interface that was visualized to provide ease of connectivity to PCs. With features such as high speed and hot "pluggability", USB has become a de-facto standard for various consumer and peripheral devices. USB connectivity standard allows up to 127 devices connected to a Host System. The current standards of USB allow data transfer rates of 1.5 Mbps, 12 Mbps and recently 480 Mbps. USB enables low, medium and high-speed connectivity between computers and peripheral devices, including keyboards, mice, printers, scanners, joysticks and cameras, using plug and play technology.
Hi-Speed USB extends the speed of the connection from 12 Mbps on Original USB up to 480 Mbps on Hi-Speed USB, providing an attachment point for next-generation peripherals which complement higher performance PCs and user applications. Hi-Speed USB is both forward and backward compatible with Original USB, resulting in a seamless transition process for the end user. In fact, Hi-Speed USB uses the same cables and connectors as Original USB. Hi-Speed USB offers a compelling opportunity for peripherals vendors to migrate their USB peripherals to higher performance, while still being able to sell the same peripherals into the huge installed base of USB-capable PCs. Hi-Speed USB is also expected to lead to the development of higher performance peripherals that will bring new applications to the PC.
USB emerged in late 1995 from the shortcomings of peripheral devices implementation. Shortly after its introduction, USB became widely popular and is now the clear ubiquitous connectivity in PCs and peripheral devices. USB continues to be dominant for the following reasons:
•Mature, proven technology;
•Easy plug and play.
As evidenced by USB popularity, several extensions of the technology have been introduced recently to try and capitalize on its installed base/ popularity. An example of this extension, which is supported and approved by the USB Implementers Forum (USB-IF), is USB On-The-Go (OTG). In addition, several products that have traditionally been 1394-based such as digital camcorders are now coming to market with USB 2.0.
•Ubiquitous PC and peripheral connectivity today;
•Seamless forward/backward compatibility between USB 1.1 and USB 2.0 devices;
•Enables plug n' play and "hot-swapping", thus no need for messy configurations and for users to stop or restart the PC to connect a USB device;
•Allows for easy expansion, a single USB port is able to support up to 127 devices;
•Mixed peripheral support for varying bandwidth rates of 1.5,12,480 Mbps.