A yellow or amber light might indicate that the device is in a warning or caution state, such as when it's booting up or when there's a problem with the connection. There are no specific requirements for this document. This includes Doppler. The lights on your ONT are typically LED indicators that display different colors and patterns to convey information about the device's status. On most models — including the Langzhi L801, L880G, and L881G — you'll find the indicator lights on the front panel, usually with small icons or text labels underneath. You can also monitor the status of the fan tray assembly and the power supplies.