AV Cabinet 12 Volt Trigger Controlled Cooling Fan System, with Multi-Speed Fan This 120mm cooling fan unit is designed to be mounted inside your equipment cabinet. It will quietly pull the warm air out of your cabinet and exhaust it out the back or top. It has a high-quality, low-noise 120mm fan, with long-lasting and quiet fluid dynamic bearings. The system has a 12 volt trigger control module, which turns the fans on and off, by monitoring your receiver's 12v trigger socket. This module sends power from the multi-voltage transformer (included in the system), which runs the fans. IMPORTANT: Some receivers have a non-standard setup, where the receiver doesn't directly control the trigger (for example, the trigger might be under the control of Zones 2 or 3, etc.). Please consult your receiver's manual for details about how its 12v trigger operates, or contact me if you have questions. Recommended fan speeds: The 120mm fan is rated at 19 db, while moving 55 cubic feet of air per minute (3/4 speed). The fan has approximately these specs at different speeds: 1/3 speed = 25CFM at 10db, 1/2 speed = 37CFM at 13db, 2/3 speed = 49CFM at 16db, and full speed = 74CFM at 22db (approximate). With cabinet cooling, slow (and quiet) are the way to go! The cooling fan unit measures 6-1/4 square, by 1-1/2" deep.