(from the customer) capacity. Wireless services, including Wi-Fi, WiMAX, LMDS, MMDS, satellite, cellular, microwave, and others represent alter- native options for access connectivity. All of these will be discussed in greater detail later in the book. Miscellaneous Additional Terms A number of other terms need to be introduced here as well, beginning with data terminal equipment (DTE) and data circuit terminating equipment (DCE). DTE is exactly that-it is the device that a user employs to gain access to the network. A DCE is the device that actually terminates the circuit at the customer's premises, typically a modem. The relationship between these network elements is shown in Figure 1-7. One important point: Because the bulk of the usage is over the public switched telephone network (PSTN), which is optimized for the transport of voice, the primary role of the DCE is to make the customer's DTE look, smell, taste, and feel like a telephone to the network. For example, if the DTE is a PC, then the modem's job is to collect the high-frequency digital signals being produced by the PC and modulate them into a range of frequencies that are acceptable to the bandwidth-limited voiceband of the telephone network. That's where the name comes from, incidentally-modulate/demodulate (MO-DEM). Another pair of terms that must be introduced here is parallel and ser- ial. You have undoubtedly seen the ribbon cables that are used to trans- port data inside a PC (Figure 1-8) or the parallel wires etched into the motherboard inside the PC (Figure 1-9). These parallel conductors are called a bus, and are used for the high-speed transport of multiple simul- taneous bits in parallel fashion from one device inside the computer to another. Serial transmission, on the other hand, is used for the "single- file" transport of multiple bits, one after the other, usually deployed out- side a computer. Figure 1-7 The relation- ship between the DTE and DCE in a (Computer) (Modem) (Modem) (Computer) typical network Downloaded from Digital Engin