What does each LED light on the EX6120 indicate?

The Router Link LED (amber, green, or red) shows the connection quality between the extender and router. The Device Link LED shows the connection between the extender and your computer/WiFi device using the same color scheme (green = best, amber = good, red = poor, off = no connection). The Power LED shows amber while booting, solid green when powered on, and is off when powered off. The WPS LED shows solid green when WPS is enabled or blinks green during a WPS connection attempt.