e 6509 takes up 21 RU. A seven-foot telecom rack is 40 RU, SO these larger switches use up a significant portion of the available space. The larger chassis switches are very heavy, and should be installed near the bottom of the rack whenever possible. Smaller chassis switches (such as the 4506, which takes up only 10 RU) can be mounted higher in the rack. Always use a minimum of two people when lifting heavy switches. Often, a third person can be used to guide the chassis into the rack. The chassis should be moved only after all the modules and power supplies have been removed. Power Each module will draw a certain amount of power (measured in watts). When you've determined what modules will be present in your switch, you must add up the power requirements for all the modules. The result will determine what size power supplies you should order. To provide redundancy, each of the power supplies in the pair should be able to provide all the power necessary to run the entire switch, including all modules. If your modules require 3,200 watts in total, you'll need two 4,000-watt power supplies for redundant power. You can use two 3,000-watt power supplies, but they will both be needed to power all the modules. Should one module fail, some modules will be shut down to conserve power. Depending on where you install your switch, you may need power supplies capable of using either AC or DC power. In the case of DC power supplies, make sure you specify A and B feeds. For example, if you need 40 amps of DC power, you'd request 40 amps DC-A and B feeds. This means that you'll get two 40-amp power circuits for failover purposes. Check the Cisco documentation regarding grounding information. Most collocation facilities supply positive ground DC power. Chapter 2: Hubs and Switches For AC power supplies, you'll need to specify the voltage, amperage, and socket needed for each feed. Each power supply typically requires a single feed, but some will take two or more. You'll need to know the electrical terminology regarding plugs an