a CDS/NTDS that normally uses a three-bay/one-bay
computer configuration to operate at full capability.
Because of a casualty to the one bay, that bay is dropped
offline. The CDS/NTDS can still perform its basic
mission, but the system is reduced because not all four
computers are being used.
Devices that are used to bring the computer to
reduced capability are switchboards and computer
control panels. The operational program (software)
must also be reconfigured to reflect the hardware
reconfiguration. This can be accomplished at an I/O
device using operating system functions (commands).
Again refer to the SOMs or CSTOMs for exact details
of your system’s capabilities and limitations and the
hardware and software required to reconfigure it.
OPERATIONAL REQUIREMENTS OF
COMPUTER SYSTEMS
Effective operation of computer systems also
depends on security and on controlling electromagnetic
disturbances. You’ll need to pay particular attention to
ADP security and electromagnetic interference (EMI).
Lack of attention to these factors can seriously
jeopardize the security and operation of a computer
system.
ADP Security
The security of computers depends on
administrative and physical controls.
The
administrative requirements (directives and
instructions) will provide the policy and procedures to
follow to meet the physical requirements. Let’s
highlight some of the things you will handle on a regular
basis that require protection to ensure the security of the
computer system.
Data and information —For tactical and tactical
support systems, the data the computer handles and
makes available is classified. (Includes COMSEC
material for tactical data links).
Passwords —Used with nontactical systems
(SNAP) to ensure only authorized users gain access to
the computer system.
Operational programs on magnetic tape, disk,
and disk packs—For tactical and tactical support
systems, these programs and any revisions (program
patches) are classified. For nontactical systems, the
operational programs may be copyrighted and require
protection to avoid misuse.
1-14
Safe combinations —For controlled spaces
where computers are used.
Computers —Computers must be safeguarded;
they are an ADP asset.
Be sure you know where the emergency destruction
procedures for the computer system are. They should
be readily available. For more detailed information on
guidelines that will aid in the security of computers,
refer to OPNAVINST 5239.1, Department of the Navy
Security Program for Automatic Data Processing
Systems and OPNAVINST 5510.1, Department of the
Navy Information and Personnel Security Program
Regulation.
Electromagnetic Interference
Electromagnetic interference (EMI) is an
electromagnetic or electrostatic disturbance that causes
electronic equipment to malfunction or to produce
undesirable responses or conditions that do not meet the
requirements of interference tests. You must be more
aware of the problems EMI causes and the solutions
required to resolve these problems. No magic is
involved in reducing or eliminating EMI. Everyday
common sense approaches to maintaining equipment
will resolve many problems caused by EMI.
TYPES OF EMI. —There are three types of
EMI—natural, inherent, and manmade.
Natural EMI. —Natural interference is caused by
natural events, such as snowstorms, electrical storms,
rain particles, and solar radiation. It can cause problems
with rf data links between shore, ship, and air, but few
problems with modem digital data equipment.
Inherent EMI. —Inherent interference is noise
within a piece of electronic equipment and is caused by
thermal agitation or electrons flowing through circuit
resistance.
Manmade EMI. —Manmade EMI is produced by
a number of different classes of electrical and electronic
equipment. The equipment includes, but is not limited
to, transmitters, welders, power lines, motors and
generators, lighting, engines and igniters, and electrical
controllers. A number of these devices can cause severe
EMI, which can degrade the operation of shipboard and
shorebased computer systems.
EMI can be classified by its spectrum distribution.
It can be either broadband or narrowband interference.
These terms refer to the frequency spectrum the
interference covers.
