scussion, the switches and lines that compose a network are owned and managed by a single firm. This is the same as a manufacturing firm owning and managing its equipment and other facilities. Networks in Telecommunications Access refers to connections that are external to the network and mediated by market transactions. For any given network, there are nodes and links that are outside the network. For example, in a telecommunications network, customer premises equipment and local area networks are attached to the network but lie outside its boundaries. When there are multiple networks that interconnect, each network is independently owned and managed. When independent companies have platform access, the activities of the companies that supply complementary products are outside the network even if they provide services that are transmitted by the network. This discussion has established that the physical shapes of networks are distinct from the economic relationships that govern networks. Two sets of nodes and links may be identical in terms of physical facilities but very different in terms of the economic relationships that establish those networks. For example, one network could be owned and operated by a single firm, whereas another identical set of nodes and links may be formed by two interconnected networks, with each of the two networks owned and operated by different firms. For example, in Figure 1.13, the interconnected networks could compose one network (with a solid line showing the connection) or they could be distinct networks. 4. Platform Access Platform access refers to technological standards that allow suppliers of comple- mentary services to supply their products to customers of the network's services. Platform access can include access to the network's transmission services SO that the supplier can provide services over the network and the network's customers can receive the complementary services. It can also include the ability of suppliers of complementary services to know and use the techno