Data Communications Networking Devices - 4th Ed.pdf

484 _________________________________ WIDE AREA NETWORK TRANSMISSION EQUIPMENTFigure 4.68 A variety of methods can be used to connect a terminal to a computer locatedin the same buildingconvert it to a repeater by setting the delay to zero, setting the clock to external, andusing a short pigtail cable to reverse the signals.Figure 4.68 illustrates a typical application where line drivers would be installed.In this of®ce building the computer system is located in the basement. The threeterminals to be connected to the computer are located on different ¯oors of thebuilding. A remote terminal located on the second ¯oor of the building is only 100feet from the computer and is directly connected by the use of a low-capacitanceshielded cable. The second terminal is located on the eighth ¯oor, approximately500 feet from the computer and is connected by the use of line drivers to extend thesignal transmission range. A third terminal, located on the 30th ¯oor, uses a pair oflimited-distance modems for transmission since a large number of line driverswould be cost-prohibitive.4.8 LIMITED-DISTANCE MODEMSAs the name implies, limited-distance modems are designed for data transmissionover relatively short distances when compared to traditional modems. Theutilization of such devices can result in dramatic savings in comparison to thecost of using conventional modems for the transmission of data over shortdistances. These devices have operating rates ranging from 110 bps to over 1million bps for distances ranging from 1 to 20 miles or more. Names given to these