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A UPS is a battery backup device that can supply power to your plugged-in notebook or (more likely) desktop computer if AC power fails. For example, I'm writing this in the foothills of the Rocky Mountains, where power glitches occur so frequently that no VCR in the county displays the correct time. Many UPS devices can communicate with your PC via a serial cable. That way, the UPS can let your PC know when AC power has been lost or when the UPS battery is low.
To set up your UPS, first install it according to the manufacturer's instructions, then click the Select button on the UPS tab of the Power Options control panel. You can specify the vendor, model, and which serial port the UPS attaches to (you may need to use a special cable supplied by the UPS manufacturer).
To configure your UPS, click the Configure button on the UPS tab of the Power Options control panel. The options you can set here include:
* Enabling notification messages of power failure, power restoration, low battery condition, and UPS-to-computer communication.
* If you enable notification messages, setting a time after a power failure that Windows XP waits to display a message the first time and how long it waits to display subsequent messages.
* Specifying when Windows issues a critical alarm if the UPS didn't issue one automatically because of a low battery. Enter the number of minutes you feel confident the UPS can run your PC. This is a belt-and-suspenders setting just in case the low-battery-sensing feature of the UPS fails.
* Running a program (if any) when a critical alarm occurs. The UPS vendor typically provides such a program.
* Shutting down or (if hibernation is enabled) hibernating after the vendor-supplied program runs.
Infrared and Wireless Devices
Windows XP provides infrared and wireless device support equivalent to that of Windows Me and superior to that of Windows NT Workstation 4.0. With a wireless link, you can transfer files between two computers, print a document from a computer to a printer, or download a file from a digital camera, without an interconnecting cable. (Better have a good clear line of sight, though.)
Heck, you can even create a network link, which you accomplish via the New Connection icon in the Network Connections control panel. The procedure is very similar to creating a Direct Cable Connection link: You specify one machine to be the 'host' and the other to be the 'guest.'
The most common wireless device is the infrared link. Infrared light has a wavelength longer than visible red light (and a frequency less than red light). In the personal computer world, nearly all infrared devices adhere to one or more of the various IrDA (Infrared Data Association) standards, which lay out as follows:
* IrDA-SIR, an older device standard, specifies a speed of 115Kbps.
* IrDA-FIR specifies 4Mbps.
* IrDA-VFIR specifies 16Mbps.
IrDA-SIR, IrDA-FIR, and IrDA-VFIR are half-duplex systems. That is, communication only occurs in one direction at a time.
Other standards you may need to know for the exam are as follows:
* IrTran-P is an image transfer standard. (By the way, it conflicts with ActiveSync 3.0, the synchronization software for Windows CE. You have to turn off one or the other. Turn off IrTran-P in the Wireless Link control panel via the Image Transfer tab by clearing the Use Wireless Link To Transfer Images From A Digital Camera To Your Computer check box.)
* IrComm is a cell phone communications link standard.
* IrNET is a PC-to-PC networking standard.
IrDA-equipped computers and printers have a little red window somewhere on the device that acts as the line-of-sight communications port.
Windows XP normally autodetects built-in infrared devices such as often come with notebook computers, but you may have to run the Add/Remove Hardware Wizard if you're retrofitting an infrared device to a serial port. On some computers, enabling the built-in infrared port requires that a COM port be disabled in the BIOS setup program. After you do that, Windows XP will probably detect the infrared port at the next reboot via Plug and Play. After you install an infrared or other wireless device and Windows XP recognizes it, a new icon (Wireless Link) appears in the Control Panel and offers various options for notification and access control (see Figure 9-3). Also, if you run the Add Printer Wizard, a new port (IrLPT) appears in the list of available device ports.
Figure 9-3: The Wireless Link dialog box.
Time Shaver Relevant facts about infrared communications include the following:
* Windows XP can support multiple sessions (programs communicating with each other) over a single link, albeit very slowly.
* Windows XP can support multiple infrared links, too, but each infrared port can only communicate with one other infrared port at a time.
* Most infrared devices need to be within one meter of each other, and with each red window pointing at the other, to communicate.
* When two infrared devices are within range and properly positioned, an infrared port icon appears on the taskbar, and a wireless link icon appears on the desktop.