ASR 900 Series routers have a single fan tray slot, which must be populated for the system to operate. The fan tray contains redundant fans. The systems continue to operate on a single fan failure. The systems have been designed to remain operational during the replacement of the fan tray. The duration of the fan tray replacement has a hard time limit imposed on reinsertion of the fan tray depending on the system’s ambient temperature. In addition to cooling the chassis, the fan tray also contains a connector for dry-contact inputs and several system-level alarm LEDs.
