Interestingly, the converse of carrying Ethernet over existing DC or AC power wires exists and may be useful in those cases where investment has already been made in a low-voltage infrastructure.
Finally, remember the term EEPoE, which stands for Energy Efficient Power over Ethernet. With approximately 4.5 watts of power wasted on an 802.3at link after 100 meters, new EEPoE technology (see IEEE 802.3az) can cut this link loss by approximately 50 percent, reducing the power requirement of a 24-port switch by up to 50W. As green building technology continues to gain momentum, EEPoE will become significant.
Ray Coulombe is Founder and Managing Director of SecuritySpecifiers.com, enabling interaction with specifiers in the physical security and ITS markets; and Principal Consultant for Gilwell Technology Services. Ray can be reached at ray@SecuritySpecifiers.com, through LinkedIn or followed on Twitter @RayCoulombe.