Structure cabling system

A local area network comprising:

• a plurality of local area network nodes;
• a LAN switch;
• a power supply subsystem;
• and
• communication cabling connecting said plurality of nodes to said switch via the power supply subsystem for providing data communication,
• the power supply subsystem including a power management and control unit governing the supply of power to at least some of the plurality of local area network nodes via the communication cabling,
• wherein said power supply subsystem is operative to supply power to at least one of the local area network nodes via the communication cabling over wire pairs within the cabling not used for data communication,
• said power supply subsystem being operative to couple power into the communication cabling substantially without interfering with data communication and including current limiting circuitry controlling current delivered into the communication cabling,
• wherein said power management and control unit is operative to interrogate at least one node to which it is intended to transmit power over the communication cabling in order to determine whether the node's characteristics allow it to receive power over the communication cabling.