"24V DC Cooling Fan" AC distributed power system consists of multiple AC-DC conversion modules, each circuit board or a device has an AC-DC conversion module, the structure is more expensive, because each AC-DC conversion module are required a rectifier and filter circuit to suppress electromagnetic interference, but also means the AC power cord around the entire system, increasing the sensitivity of electromagnetic interference and security issues. However, in certain circumstances "24V DC Cooling Fan" structure may be the right solution. For example, a telecommunications equipment manufacturer of telecommunications equipment to take advantage of this structure of a building housing the power supply. Each floor using an AC-DC module, power distribution structure is shown in Figure 9-31. "24V DC Cooling Fan" also applies to the structure of a computer manufacturer's file server, CPU boards and every disk drives use an AC-DC power modules.