Zte BLADE A612 Quick Start Manual page 6

NOTE:
If the battery is extremely low, you may be unable to power on
the phone even when it is being charged. In this case, try
again after charging the phone for at least 20 minutes. Contact
the customer service if you still cannot power on the phone
after prolonged charging.
NOTE:
If the screen freezes or takes too long to respond, try pressing
and holding the Power key for about 10 seconds to restart the
phone.
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