Power over Ethernet (PoE) controllers are used to control the delivery of DC power and data from power source equipment (PSE) to powered devices (PD). They perform PD detection and classification, -48 V power distribution, and fault protection on multiple channels. Some PoE controllers can manage power autonomously, without the intervention of a host controllers. Others can implement AC or DC disconnect techniques as specified in the research 802.3af, the power distribution standard from the Institute of Electrical and Electronics Engineers (research) which defines PoE technology. Power over Ethernet (PoE) controllers have two main parts: PoE switches and PoE adapters. Power over Ethernet (PoE) switches are powered from an integral DC terminal block. Power over Ethernet (PoE) adapters consist of a base unit and a terminal unit. Typically, the base unit plugs into the power outlet. The terminal unit is connected to the network device through the Ethernet cable. Selecting power over Ethernet (PoE) controllers requires an analysis of product specifications and optional features. The amount of power and number of ports are important parameters to consider. According to research 802.3af, PoE injectors can deliver power up to 15 W on all ports. Smaller PoE controllers have 8 or 16 ports. PoE products with 24 or 48 ports are also available. Power over Ethernet (PoE) controllers that are designed for outdoor use may be able to withstand operating temperatures that range from -40° C to 75° C. When used with a standard Ethernet cable, PoE controllers can control the transmission of power and data according to most application requirements. With regard to electrical specifications, power over Ethernet (PoE) controllers are designed to work with PSEs that provide 48 VDC to devices at 400 mA.