Models :

DHI-VTH2421FB,DHI-VTH2421FW,DHI-VTH5221D-S2,DHI-VTH5221DW-S2,DHI-VTH5241DW-S2,DHI-VTH5441G,DHI-VTH2421FB-P,DHI-VTH2421FW-P,DHI-VTH5421E-H,DHI-VTH5421EW-H,DHI-VTH2421FW-P-USA


Online upgrade steps: 
1.Upgrade part1 
2.Upgrade part2 after part1 is successfully upgraded.