Nokia Lumia 900 - Manual (Page 11)

Set the keys and screen to lock automatically
Tap Settings > lock+wallpaper > Screen times out after, and select the length of time after which
the keys and screen are locked automatically.
Connect the headset
Enjoy your favorite music, or free your hands for other things when in a call.
Connect the headset to your phone.
Do not connect products that create an output signal, as this may damage the device. Do not connect
any voltage source to the audio connector. If you connect an external device or headset, other than
those approved by Nokia for use with this device, to the audio connector, pay special attention to
volume levels.
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