The IEEE 802.3af standard defines two different types of PSEs: endspan and midspan. An endspan PSE integrates the power sourcing functionality with a network switch. This device can be 8-port, 12-port, 24-port or more with the capability of delivering power on any one or all of those ports. One of the disadvantages is the majority of the installed switches in existing networks still are not 802.3af compliant so there is no protection against equipment damage.