Universal Serial Bus technology now makes it easy for PC users to connect monitors, printers, digital speakers, modems and input devices like graphics tablets, scanners, digital cameras, joysticks and multimedia game equipment. Here's a glimpse at the technical side of USB. Two data rates USB has two data rates, 12Mbps for devices requiring increased bandwidth, and 1.5 Mbps for lower-speed devices like joysticks and game pads. Tiered-star topology USB uses a "tiered star topology" which means that some USB devices--called USB "hubs"--can serve as connection ports for other USB peripherals. Only one device needs to be plugged into the PC. Other devices can then be plugged into the hub. USB hubs USB hubs may be embedded in such devices as monitors, printers and keyboards. Stand-alone hubs could also be made available, providing a handful of convenient USB ports, right on the desktop. Hubs feature an upstream connection (pointed toward the PC) as well as multiple downstream ports to allow the connection of additional peripheral devices. Up to 127 USB devices can be connected together in this way. Automatic configuration USB host controllers (which are available as part of several Intel PCI chip sets) manage and control the driver software and bandwidth (data flow) required by each peripheral connected to the bus. Users don't need to do a thing, because all the configuration steps happen automatically. The USB host controller even allocates electrical power to the USB devices. Like USB host controllers, USB hubs can detect attachments and detachments of peripherals occurring downstream and supply appropriate levels of power to downstream devices. Electrical power Another word about electrical power. Since power is distributed through USB cables (with a maximum length of five meters), you no longer need a clunky AC power supply box for many devices. The bottom-line is that USB makes it easy to add peripherals to your PC, and that can make your PC more productive and fun to use.

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