However, as good as 802.11n is, few if any unlicensed wireless technologies are completely immune to interference and range limitations, which is why the inclusion of a hard drive is a great boon for this device class.

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But it uses a lot of battery power, and the 2.4 GHz spectrum is also widely in use by devices like Wi-Fi networks--and cordless phones and microwave ovens can cause interference in that range.

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Kindle Fire HD can switch automatically between the 2.4 GHz network and the newer, less crowded 5 GHz network, resulting in better range and less interference.

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That enables control over interference, which in turns boosts range and device density.

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With the highest level of noise immunity, ClearPad 3400 performs with precision even in the presence of noise interference, which can be exacerbated by a range of factors, including the use of noisy handset power supplies.

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Investigators of the February crash found that interference from PLBs carried by passengers had caused the "smart" long-range rescue beacons on the aircraft and life rafts to shut down.

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