rst network is T2 - T1. If V - C - Vo - Co < T2, the incremental value of the first network is either (V - C - Vo - Co) - T1, which is therefore less than T2 - T1, or possibly zero, if the first network does not yield a positive benefit. Thus, with multiple substitutes for a network service, the value created by a network service is the incremental cost efficiency, if any. There is a tendency to confuse the output of a network, that is, the network's transmission, transportation, or delivery services, with what is moved by the net- work. For example, the purpose of an electric power transmission network is to move electric power from a point of generation to a point of consumption, or more generally from a point of surplus to a point of deficit. The output of the electric power network is not electric power, only the transmission of that power. The output of the electric power grid is the transmission service itself. The Structure and Functions of Networks As another example, a cable television network is used in the provision of entertainment, news, advertising, and other content to viewers. The output of the cable television network is the transmission service. The content is produced by content providers. Although important, this distinction may pose some difficulties when content providers are vertically integrated with the cable television network. However, this is similar to a manufacturer engaged in wholesale delivery. The network still represents a set of facilities and activities that are distinct from those used in the creation of content. Other than the physical difference between these types of facilities and activities, a good way to understand this distinction is by noting that some of the content carried by cable television companies is created by independent companies. Thus, network services are distinct from what is transmitted, transported, or distributed. In addition, the network's output of services should not be confused with the inputs used to establish, operate, or maintain the network. Man