Definition of a Universal Serial USB Bus Port
USB, an acronym for universal serial bus, is a standardized interface that allows peripheral devices to be connected to a computer. Virtually all computers manufactured since early 2000 are equipped with USB ports, and the technology has cross-platform compatibility, meaning that it can be used to attach devices to Macintosh, Windows and Linux/UNIX computers. USB-enabled devices may be attached and disconnected from a computer while the computer is on, a process known as 'hot swapping.'
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Features
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USB is an extremely versatile interface, compared to older interfaces such as serial and parallel connections. USB is supported by and compatible with all operating systems. With the increasing popularity of USB as the new interface of choice, operating system developers such as Microsoft and Macintosh-integrated drivers for a range of common USB-enabled devices. This preparedness meant that USB-enabled hardware components could be activated by simply plugging it into the computer. If the OS is not able to automatically locate and install a driver, the device's self-contained driver can be used to install the device.
Transfer Rates
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The first USB standard, referred to as USB 1.0, had a data transfer rate of 1.5 Mbps (megabits per second). The transfer rate is significant, because it may limit devices in which performance is evaluated by its data transfer rate, such as flash drives. A computer that has hardware and software compatibility for faster USB standards will be able to transfer more data in a given time. USB popularity soared with Revision 1.1, a standard that supported up to 12 Mpbs; today, the most common USB interface is USB 2.0, which can handle rates of up to 480 Mbps.
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Connection Types
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There are two common connection types. USB-A is a flat rectangular arrangement that plugs into computer USB ports, and USB-B is a slightly smaller, square connector that plugs into USB ports of peripheral devices such as external hard drives, printers and scanners. Some devices such as digital cameras and mobile phones may have a USB-B variant known as Mini-B, which is smaller than USB-B. Other lesser-known proprietary connections are also used is some devices.
Streamline Effect
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Some computers actively using the USB interface may suffer from the 'streamline effect,' which affect devices such as keyboards and mice. These are examples of input devices that require a constant interface with the computer. If a computer's keyboard and mouse do not have dedicated USB ports, input functionality of either of the devices may be impaired due to the streamline effect. This problem can also arise when devices such as scanners and printers share the same USB hub, and limitation manifests itself when the two devices are used simultaneously. If the computer sends an instruction to carry out a print job and the scanner is also busy, either one of the devices will have to wait for the other to execute its instructions first.
Length Limitation
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The biggest limitation of the USB interface is its length limitation. A computer will not be able to properly communicate with a USB-enabled device if the connecting cable is longer than fifteen feet. This restriction is imposed by the nature of data flow through USB cables. This restriction may be overcome by using repeater extensions, which are cables with boosters on one end that receive and propagate the signal along in a way that retains data integrity. Repeater extension cables can be used to raise the cable length limit to eighty feet.
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References
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