 - IR wireless is the use of wireless technology in devices or systems that convey data through infrared (IR) radiation. Infrared is electromagnetic energy at a wavelength or wavelengths somewhat longer than those of red light. The shortest-wavelength IR borders visiblered in the electromagnetic radiation spectrum;the longest-wavelength IR borders radio waves.Some engineers consider IR technology to be a sub-specialty of optical technology. The hardware is similar, and the two forms of energy behave in much the same way. But strictly speaking, "optical" refers to visibleelectromagnetic radiation, while "infrared" is invisible to the unaidedeye. To compound the confusion, IR is sometimes called "infrared light." IR wireless is used for short- and medium-range communications andcontrol. Some systems operate in line-of-sight mode; this means that theremust be a visually unobstructed straight line through space between the transmitter(source) and receiver (destination). Other systems operate in diffuse mode,also called scatter mode. This type of system can function when the sourceand destination are not directly visible to each other. An example is a televisionremote-control box. The box does not have to be pointed directly at the set,although the box must be in the same room as the set, or just outside the room with thedoor open. IR wireless technology is used in intrusion detectors; home-entertainment control units; robot control systems; medium-range, line-of-sight laser communications; cordless microphones, headsets, modems, and printers and other peripherals. Unlike radio-frequency (RF) wireless links, IR wireless cannot passthrough walls. Therefore, IR communications or control is generally not possible between different rooms in a house, or between different houses in a neighborhood (unless they have facing windows). This might seem like a disadvantage, but IR wireless is more private than RF wireless. Some IR wireless schemes offer a level of securitycomparable to that of hard-wired systems. It is difficult, for example, toeavesdrop on a well-engineered, line-of-sight, IR laser communications link.
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20 Oct 2008
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