18 August 1998
electrical utility systems. The central station or island station LAN may be extended to the additional
workstations or they may communicate with the LAN using a network modem.
b. The workstation is a complete microcomputer system consisting of a system unit with central
processing unit, memory, input-output interfaces, keyboard, monitor, mouse or trackball, hard disk drive,
floppy disk drives, cartridge tape drive and CD ROM drive. Since the UMCS operator requires clear
graphic displays which are easily viewed and recognized, the operator workstation monitor will not be
smaller than 17 inches (nominal diagonal screen measurement). A block diagram of an operator
workstation is provided in Figure 3-7.
Figure 3-7. Workstation with Laser Printer.
11. LOCAL AREA NETWORK.
a. A LAN is a system composed of hardware, media (cabling) and software which allows
computers to share information and resources. The central station or island station LAN will be
configured in a bus or star topology as shown in Figures 3-8 and 3-9. In a star topology, cables from
network devices are connected to a hub which passes data signals between connected ports. The LAN
will utilize fiber optics, twisted pairs, coaxial cable, or radio frequency (RF).
b. Two or more LANs may be interfaced together using dedicated communication circuits, switched
circuits, or a packet RF data transmission system to form a wide area network (WAN). Connection of the
WAN requires network devices such as network modems or remote bridges at each connected LAN.
Figure 3-8. Central or Island Station LAN using a Bus Topology.