Yealink T21PE2 - Firmware and Upgrading Issues; Fail to Upgrade the Phone Firmware; Verifying the Firmware Version

Administrator’s Guide for SIP-T2 Series/T4 Series/T5 Series/CP920 IP Phones
536
Firmware and Upgrading Issues
Fail to upgrade the phone firmware
Do one of the following:
l Ensure that the target firmware is not the same as the current firmware.
l Ensure that the target firmware is applicable to the IP phone model.
l Ensure that the current or the target firmware is not protected.
l Ensure that the power is on and the network is available in the process of upgrading.
l Ensure that the web browser is not closed or refreshed when upgrading firmware via web user interface.
Verifying the firmware version
Press the OK/√key when the IP phone is idle to check the firmware version. For example: 28.82.0.20.
Item Description
1 28
Firmware ID.
The firmware ID for each IP phone model is:
l 70: T54S/T52S
l 35: T48G
l 28: T46G
l 66: T48S/T46S/T42S/T41S
l 29: T42G
l 36: T41P
l 54: T40P
l 76: T40G
l 46: T29G
l 69: T27G
l 44: T23P/G
l 52: T21(P) E2
l 53: T19(P) E2
l 78: CP920
2 82
Major version.
Note: The larger it is, the newer the major version is.
3 0 A fixed number.
4 20 Minor version.