Yealink SIP-T21 - Manual (Page 13)

Overview
3
Icons appearing on the LCD screen are described in the following table:
Icon Description
Network is unavailable
Registered successfully
Register failed
Registering
Hands-free speakerphone mode
Handset mode
Headset mode
Multi-lingual lowercase letters input mode
Multi-lingual uppercase letters input mode
Alphanumeric input mode
Numeric input mode
Multi-lingual uppercase and lowercase
letters input mode
Voice Mail
Text Message
Auto Answer
Do Not Disturb
Call Forwarded/Forwarded Calls
Call Hold
Call Mute
Ringer volume is 0