Demonstration circuit 1567B features the LTC4274, a single power sourcing equipment (PSE) controller designed for use in IEEE 802.3 Type 1 and Type 2 (high power) compliant Power over Ethernet (PoE) systems. The LTC4274 is configured in the DC1567B as a midspan power injector where data comes in from an existing network system and out, along with power, to a powered device (PD). The LTC4274 autonomously detects and classifies a PD, turns power on to the port, and disconnects port power without the need for a microcontroller. A two second backoff timer supports the midspan configuration. A 55V nomical supply is recommended to power the demo board.