from dedicated line to DDD. 2.6 MULTIPLEXING REDUCES COMMUNICATIONS COSTS Multiplexers eliminate the cost of many individual communication lines and modems to support communications between central com- puter sites and remote terminals, by combining the individual trans- missions on a single line. The value of multiplexing is realized when the cost of separate lines and modems exceeds the cost of a single line, a pair of modems, and back-to-back multiplexers. Multiplexers are adaptable to a wide variety of configurations to achieve the objective of reduced operating costs. Equally important, multiplexers accommodate growth in traffic volume without the need for additional lines. Large scale multilink multiplexers link nodes within a multinode network. This arrangement benefits the exchange of data between the different nodes, which may be located in dif- ferent cities, and provides multiple data paths to reroute data in the event of a link outage. Multiplexers can also accommodate low-speed asynchronous terminals with different transmission rates over DDD lines, eliminating the cost of separate lines and ports to support the different transmission rates. Multiplexers are available in a wide range of channel capacities to satisfy small, medium, and large scale network requirements. Models are available to support as few as four or eight terminals and/or lines, while top-of-the-line models are available with more than 200 ports. Medium and large scale units are easily expanded to meet growth requirements or reconfiguration needs. Most state-of-the-art multiplexers are available with an integral composite link modem. This eliminates the added cost of a separate modem, saves space, and puts multiplexer and modem under the same service umbrella. A typical multiplexer system with a computer located in New York MODEMS AND MULTIPLEXERS 23 City and eight remote terminals in Denver is shown in Fig. 2-4. The multiplexers allow eight terminals in Denver to share one telephone line where previously eight lines were required. 