Power Over Ethernet circuitry offers the advantage of using existing Ethernet interfaces to transmit power to remote applications. Many applications employ Power Over Ethernet technology – including wireless access points, enterprise switches, Voice over IP Telephony and digital surveillance cameras. A typical PoE circuit consists of Power Sourcing Equipment (PSE) and a Powered Device (PD). The Power Sourcing Equipment injects ±48V DC voltage onto one Ethernet twisted pair and the return path (0V) on another twisted pair, thus supplying DC power to the Powered Device (PD). In addition to ESD, cable discharge and lightning transients, supplying DC power over Ethernet twisted pair can cause some additional transient threats unique to Power Over Ethernet circuitry. For example, consider the case where a “live” PoE Ethernet cable is being plugged into a Powered Device.  During the plug-in of the RJ-45 Ethernet connector, the Ethernet pin mating may not occur simultaneously. At the instant that the pins mate, it is possible that connection is established at pin 1 prior to or just after contact is made to pin 2. In this instant of mismatch, a 48V differential transient with respect to the line pair can result, leading to disruption or damage of the PHY or PoE circuit.