The IEEE 802.3af (June 2003) standard that defines how power is delivered over twisted pair to devices also using 10Base-T, 100Base-T, and 1000Base-T technologies. PoE provides electrical over two Cat 5e or Cat 6 wire pairs separate from those used for data transmission, except in the case of 1000Base-T. PoE not only provides an alternative to expensive electrical cabling in hard-toreach places, but also alleviates concerns about power outages if an uninterruptible power supply (UPS) is available. PoE specifies that the power sourcing equipment (PSE), or power injectors, provide output of 48V DC power over the cable plant to terminal units that provide 12V DC output to PoE-compliant devices known as powered devices (PDs). The 802.3af standard also specifies four different power draw levels of up to 3.84W, 6.49W, 12.95W, and 15.4W for attached devices.The PSE automatically senses the power requirements of the PDs, including IP phones typically drawing 3-5W, wireless access points (APs) typically drawing 6-10W, and security cameras typically drawing 9-12W. PoE typically involves power supplied directly from an Ethernet switch to a client device, although there are provisions for midspan power injectors. See also 10Base-T, 100Base-T, 1000Base-T, AP, Cat 5e, Cat 6, DC, Ethernet, LAN switch, UPS, and volt.