Different modules require different amounts of power. Inline power modules supply power to IP phones. Cisco has an inline power module specifically designed to power IP phones. It is essential to choose the correct power supply to support the various line cards, modules, and supervisor engines on the switch. Cisco offers a tool called the Cisco Power Calculator, which can be used to select the appropriate power supply for your switch. Launch the Cisco Power Calculator and fill out the product family, supervisor engine, input voltage, line cards, and the number of PoE devices. IP phones are an example of PoE devices, and most IP phones belong to the IEEE 802.3af Device - Class 2 (7W). The power calculator will then display the results of different power supply options, allowing you to choose the required power supply. The power supplies operate most efficiently at an input voltage between 200 and 240 volts AC.