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Thursday, June 16, 2011

WAP browsers for Windows

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sreekumar

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WAP BROWSING ON WINDOWS If you are using internet on your mobile phone ,you may have probably visited wap sites which are web sites exclu...

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Will A USB Port be burnout?

Will a usb port burn out as a result of the over current drawn from device?

The answer is NO.

The specification defines a low-power device as one that draws up to 100 milliamperes from the bus, and a high-power device as one that draws up to 500 milliamperes from the bus. A high-power device can't draw more than 100 milliamperes until the host has said it's OK to do so.

All hubs have over-current protection that prevents excessive current from flowing to a device. If you connect a high-power device to a low-power hub, Windows will display a message informing you that the hub doesn't have enough power available and offering assistance. If the bus has a low-power device connected to a high-power port, Windows will recommend swapping the device with the

high-power device (Figure1)

Figure 1: Windows warns users when they connect a high-power device to a

low-power hub, and helps them find an alternate connection.

Powering options for hubs are similar to those for other devices. all hubs except the root hub are self-powered or buspowered.The root hub gets its power from the host. If it supplies 100 milliamperes, the hub is defined as a low-power hub. High power root hub is capable of supplying 500 milliamperes to each port on the hub. Bus-powered hubs are limited. All of a bus-powered hub's downstream devices must be low power. A self-powered hub may also draw up to 100 milliamperes from the bus. When the port circuits on a hub detect an over-current condition, they limit the current at the port and the hub informs the host of the problem. Windows warns the user when a device

exceeds the current limits of its hub port (Figure 2).

Figure 2: When a device exceeds the current limit of its hub's port, Windows

warns the user and offers assistance.

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