How to force my Motorola Nextel I1 to reboot or restart when screen is frozen or phone is locked up?

How to force my Motorola Nextel I1 to reboot or restart when screen is frozen or phone is locked up?

In the unlikely event that your Motorola Nextel I1 becomes unresponsive, try a force reboot.

Warning: Don’t attempt to remove or replace the battery yourself doing so may damage the battery and could cause burning and injury.

To reboot the device, press and hold the power key + volume down key for 10 seconds.

Notes:
Data on your Motorola Nextel I1 will not be deleted.
Ensure that your Motorola Nextel I1 is charged to a minimum of 5%. If your battery is below 5% then the device will not power on. A device that is completely drained should be charged, for a minimum of 15-20 minutes, using the provided wall charger.