White Paper on the subject of the AC coupled diode discovery method

The electrical power used by computing and networking devices is most often taken for granted; we just assume that the power is working properly, and we don't really care how it works. There is, however, a large class of low power network appliances and devices for which it is either too expensive or too awkward to physically hook up power in the conventional way. Still other remote devices are in need of multiple and redundant power sources to improve communication uptime and reliability. Furthermore, devices such as IP telephones would be simpler if they needed only a single cable for data and power. A method is proposed for the discovery of DTE "powerable" devices through a unique digital signature. Powerable, or powered devices are designed to take power off of the UTP data cable, allowing both power and data to use the same cable. A discovery process, located in the Power Sourcing Equipment, looks for a unique identity network, located in the DTE, or Powered Device at the other end of the link. Once the discovery process is successful, the application of power on the UTP data cable is possible and generally safe. Optionally, network management could be used for the control of large numbers of these types of powered links, therefore allowing for the provisioning of powered devices. This paper concentrates on the data link layer implementation of the discovery and power control processes, with some references to the expected physical layer interfaces.