If your device does not come with an installed internal power supply, you can install one or two power supplies.
The 8520 Series switch supports 750 W power supply units using either AC or DC power.
All installed power supplies must have the same airflow direction (front-to-back or back-to-front) and must also match the airflow direction of the fan modules.
If the power supply module has a red tab, the airflow is front-to-back.
If the power supply module has a blue tab, the airflow is back-to-front.