VTech MI6821 User Manual page 30

In Case Of Difficulty
Common Cure For Electronic Equipment
If the unit does not seem to be responding
normally, then try to put the handset in its
base. If it does not seem to respond, do
the following (in the order listed):
1. Disconnect the power to the base.
2. Disconnect the handset battery.
3. Wait a few minutes.
4. Connect power to the base.
5. Reinstall the battery.
6. Watch for handset to display HANDSET.
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