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Universal Serial Bus. USB provides a single common interface to peripherals and plug-and-play configuration (at the host/pc).

USB was created in 1996 by a consortium of companies (let by Intel) with the aim of dramatically simplifying the connection of peripheral devices to a computer.

The original standard for USB (occasionally referred to as USB 1.0, but normally simply as USB) supported transfer speeds of 1.5Mbps and 12Mbps. USB 1.1 is a revised version of the USB specification, but the transfer rate remains unchanged. USB 2.0 (also referred to as "USB Hi-Speed) also supports 480Mbps and is otherwise backwards compatible with earlier versions. The USB specification limits maximum cable lengths to 5m for high speed USB devices and 3m to low speed devices USB.

USB 3 significantly increased the possible maximum transfer rate, but doubles the number of cables required internally to 8. The internal cables prior to USB 3 were for power, ground and a pair for differential data. USB adds two more pairs of cables for (4 additional cables).

Supported speeds Maximum cable length
1.5Mbps 12Mbps 480Mbps 4.8Gbps
USB 3.0 Supported Supported Supported Supported Cable length is not part of the USB 3 specification. Copper based cables are likely to have a maximum cable run of about 3m.
USB 2.0 Supported Supported Supported Not supported 5m
USB 1.1 Supported Supported Not supported Not supported 3m
USB 1.0 Supported Supported Not supported Not supported 3m

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