Lenovo T420 - Manual (Page 58)

Table 7. Status indicators (continued)
Indicator Meaning
The ac power adapter is attached to the computer.
The battery status indicator is off:
The battery pack of the computer is fully charged or detached.
11 Sleep (standby for Windows
XP) status
Green:
The computer is in sleep (standby) mode.
Blinking green:
The computer is entering sleep (standby) mode or hibernation
mode, or is resuming normal operation.
52 ThinkPad T420 and T420i Hardware Maintenance Manual