DFU mode is more stringent compared to Recovery.In this mode, the operating system will not boot, and the signals delivered by the USB-connection are purely technical in nature.A characteristic feature of DFU mode appears completely black or completely white screen mobile device.The only indicator of DFU is the definition of a mobile device in iTunes as "device in the mode of stabilization / recovery."
Connect your mobile device to your computer using a special USB-cable supplied.Turn off your iPhone the standard method, ie,Press and hold the Power button until the screen displays a slider labeled "Turn off".Drag the slider to the right and wait for the shutdown.
Launch the iTunes application on your computer.Press and
hold in this position the Power button and the Home for ten seconds.Release the button Power, continuing to hold the Home.Wait determining device application iTunes (ten - fifteen seconds), and release the button Home.Remember that the device screen will be completely black.Follow the steps for flashing the device.
To display the phone mode, Device Firmware Upgrade connect the mobile device to the computer using a special USB-cable.Press and hold in this position the Power button and the Home for ten seconds.Simultaneously release both buttons after ten seconds.Press the Power button to download the standard unit in the normal mode.
Another method of removing the phone from the DFU mode is the simultaneous press Home and Power buttons without connecting the device to the computer.Hold both buttons simultaneously until the Apple logo appears on the screen.Release both buttons and wait for the standard boot devices.