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USB
The Universal Serial Bus (USB) is a new device communication standard
developed by the computer and telecommunication industries. It is aimed at
replacing most of the different kind of special interfaces such as conventional
serial and parallel ports. Most of the new PCs and Macs have USB connectors at
this point, and the number of peripherals is increasing exponentially. USB
provides power to the devices connected to it. USB 1.1 provides 12 Mbit/s and
1.5 Mbit/s data transmission speeds. USB can't be used directly as a fast
connection between PCs, but there are special products which allow small scale
networking using USB bus. USB provides a powerful, hot-plug-capable,
"true plug-and-play" interface between a host computer and add-on
peripheral devices.
NOTE - "Hot-plug-capable" means that you can plug in, use,
and unplug devices without having to shut down the host computer.
These devices can be just about anything: keyboards, mice, joysticks,
telephones, scanners, printers, security dongles, microphones, speakers, floppy
drives, cameras, modems, CD-ROM drives, etc.
USB was designed to improve on earlier peripheral connection technologies.
USB allows end-users to connect peripheral devices to a host computer on the
fly, without having the user hassle with:
 | Shutting down/restarting the computer (a big plus!)
 | Opening the computer case
 | Installing a card
 | ID conflicts
 | Termination
 | Loading device drivers (although some devices may require a one-time
driver installation). |
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In addition, USB provides:
 | A "tiered-star hub" network topology, allowing for the
connection of up to 127 devices per host computer
 | Two simple, standardized plugs for the broad range of devices
 | Power for some devices directly through the USB cable
 | Support for two data rates: 1.5 and 12 megabits per second (Mbps)
 | Up to 12 Mbps performance
 | Automatic loading and unloading of drivers as needed |
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USB devices use two types of plugs, Type A and Type B:

Here are a few USB links:

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