A power supply device is described comprising a DC voltage supply, a power section connected to the DC supply for supplying DC power from the DC voltage supply to first and second outlet ports for connection to a remote device via a cable connection, a voltage boosting circuit for generating a voltage above that of the DC supply, an energy absorbing circuit connected between an output of the voltage boosting circuit and a ground potential, and a diode connection means between the first outlet port and the energy absorbing circuit. The major components of the power supply device may be implemented as an integrated circuit.