18 August 1998
a. The communication processor is provided on systems with multiple dedicated data transmission
channels (as opposed to a LAN) between the central/island station and the field equipment. The
communication processor functions as the overall communication manager, directing operator
commands, alarm messages, status information and other data between the central/island station
computer and the field equipment. On systems with LAN-compatible smart field panels, the
communication processor is not required because data transmission between the central/island station
and the field equipment is managed by the LAN using the network interface adapter.
b. The communication processor is a special purpose, dedicated processor with a single
connection to the central/island station computer and multiple interfaces for communication with field
equipment, typically 16 EIA 232 serial ports.
NETWORK INTERFACE ADAPTER.
a. The network interface adapter is provided on systems with LAN-based field equipment. The
network interface adapter provides a physical media interface and a communication protocol interface
between the central/island station computer and the field equipment LAN.
b. The network interface adapter is a special purpose, dedicated processor which is mounted
internal to the central/island station computer or interfaced to it through a communication port, with
5. HARD DRIVES. Hard drives are sealed rotating magnetic storage media integrated with the
read/write drive mechanism and controller, and mounted internal to the computer system unit. Advances
in equipment technology have resulted in the availability of hard drives with storage capacities in excess
of 1 gigabyte. Hard drives are used to store the computer's operating system software, applications
software program files, and data files requiring frequent access. Hard drives provide faster file access
than other mass memory storage devices such as floppy drives, cartridge tape drives and optical disk
drives. Hard drives will not be used as the only file archival mechanism because failure of the hard drive
requires replacement of the drive and may result in loss of all files on the drive. Mirrored hard drives or
redundant arrays of hard drives should be considered for UMCS with critical data acquisition and storage
requirements, where loss of data gathered between archival backups is undesirable. These
arrangements will provide for access to all data, even if one hard drive fails. Removable hard drives,
which are installed in PCMCIA slots, provide portability of data and can be installed in laptop PCs.
6. FLOPPY DRIVES. Floppy drives are mounted internal to the computer system unit and use
removable magnetic media (floppy disks or diskettes). Three and one-half inch floppy disks typically
store up to 1.44 megabytes of information. Floppy drives are suitable for small program file updates or for
storage and transfer of small data files between computers which are not networked together. Floppy
drives are not suitable for most file archival applications because of the low storage capacity.
7. MAGNETIC TAPE SYSTEMS. Magnetic cartridge tape systems are mounted internal to the
computer system unit and use removable magnetic tape cartridges for data storage. They can typically
store 40 to 250 megabytes of data. Magnetic tape systems are used for file archival/backup.
a. Optical drives are mounted internally to the computer system unit or provided in a separate
enclosure with an interface to the computer system unit. Optical drives are used for large file archival
applications. Optical drives utilize lasers to read data encoded as discrete variations in reflectivity on
optical media (disks). There are several types of optical drive systems which are classified based on the
type of disk used.