Asus Nexus 7 Manual Book page 102

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By default, when you open the data usage settings screen you see
the settings for mobile data: that is, the data network or networks
provided by your carrier:
It's possible to show Wi-Fi data usage settings in a separate tab.
To do so, touch the Menu icon , then Show Wi-Fi usage.
Near the top of the screen, note the on-off switch for mobile data.
The instructions that follow assume that this switch is turned on.
If it's off, you won't be able to use mobile data at all and many fea-
tures of your tablet and apps won't work correctly.
NEXUS 7 GUIDEBOOK WIRELESS & NETWORK SETTINGS 95