The alarm LED determines a status or error occurred. The status or error is posted on the console screen. LED description: Blinking Green—Controller image upgrading. Amber—Controller status activity, such as firmware upgrade. Blinking Amber—Controller error. For example, a temperature error exists. https://www.cisco.com/c/en/us/td/docs/wireless/controller/2500/quick/guide/ctr2504-qs.html#15030