Here you can select which information the "INFO" LED on the FRITZ!Box should display.

"INFO" LED  shows rate-related information lights up when WLAN is enabled lights up when an Internet connection is active lights up when a device connects via LAN lights up when USB devices are connected lights up when Do Not Disturb is active blinks for incoming calls during absence indicates new messages on the answering machine indicates new messages on the answering machine, incoming faxes and calls in absence

The "INFO" LED always flashes when the firmware is being updated and during transmission of the security settings to a FRITZ!WLAN USB Stick.