Allied Telesis AT-9448Ts/XP (Basic Layer 3) - Manual (Page 72)

Chapter 3: Troubleshooting
72
System Fault LED is Blinking
If the system FAULT LED is blinking, no action is required. A blinking
FAULT LED could indicate that a new version of the management
software is being downloaded to the switch or the switch’s is updating the
active boot configuration file. The LED stops blinking after the switch has
completed the download or updating the boot configuration file.