What do the LED lights on the AC1200 extender mean?

The 2.4 GHz and 5 GHz Link Rate LEDs show connection quality: green indicates optimum connection, amber indicates good connection, red indicates poor connection, and off means no connection. The Device to Extender LED shows green when connected to a device, amber during startup or WiFi settings application, and off when not connected. The LAN LEDs light green when an Ethernet device is connected to a port. The USB LED lights solid green when a USB device is connected.