Yealink SIP-T21 - Manual (Page 136)

User Guide for the SIP-T21P/SIP-T21 IP Phone
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take 5 minutes to complete. Please don't power off!”.
4. Click OK to confirm upgrading.
How to reset the phone?
Reset the phone when other troubleshooting suggestions do not correct the problem.
You need to note that all customized settings will be overwritten after resetting. We
recommend asking your system administrator for advice before resetting the phone.
To reset the phone via phone user interface:
1. Press Menu->Settings->Advanced Settings (password: admin).
2. Press or to scroll to Reset to Factory, and then press the Enter soft key.
The LCD screen prompts “Reset to factory settings?”.
3. Press the OK soft key.
The LCD screen prompts “Resetting…Please Wait!”.
The LCD screen prompts “Welcom Initializing…please wait”.
The phone will be reset to factory sucessfully after startup.
Note Reset of your phone may take a few minutes. Do not power off until the phone starts up
successfully.