The more recent definitions of "smart buildings" focus on the use of a "structured cabling system" or "structured connectivity solution" (SCS) to provide a common cabling foundation upon which various building services can be delivered: data networking, telephony, environmental controls, security systems, etc. As shown in the diagram at right, a SCS provides heavy-duty connectivity between the various floors of a building, as well as individual network connections to each workstation in each tenant area. The entire building SCS is connected to one or more telecommunications service providers at a "building distribution facility" (BDF).