Note: Upgrade IOS7.1.2 We do not use OTA upgrades (mobile phone upgrades) because the Ota method upgrade causes Shsh to be unavailable oh, while some devices do not support OTA method upgrades.
Preparatory work:
A computer that can surf the internet, iOS7.1.2 the latest firmware version file, and install itunes software on your computer
IPhone4 Upgrade IOS7.1.2 method
1, because we use the itunes direct upgrade will be slower, so we have to download the iOS7.1.2 the latest firmware in advance.
2, then we connect the iphone4 to the computer, if the itunes software in the computer does not open we open it again.
3, after the itunes recognition of your iphone4, we then press shift at the same time (up key) + left mouse button click on itunes Update/restore function.
4. itunes will pop up the dialog window--Please select iOS7.1.2 firmware--Click Update--wait for itunes to run.
5, successful upgrade/recovery iOS7.1.2 need to activate the device, please follow the system prompts steps to complete.
Friendly Tips
It's best to back up the data on your phone before you upgrade, because using itunes to upgrade your system can cause all of your data to be lost.