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 MIL-HDBK-232A
5.3.3.2 Electromagnetic interference (EMI)/electromagnetic compatibility
(EMC). Any installation design should include an EMC analysis as part of the
design process. Certain commercial items must comply with Federal
Communications Commission Regulations, Part 15, Subpart J, for EMI. This
should be taken into consideration when convicting the EMC analysis to
determine what benefits this requirement may have in reducing the threat of
exploitation of the system.
5.3.3.3 Interface among RED equipment. MIL-STD-188-114 defines interface
requirements for equipment in a low-level environment. The standard
recognizes, however, that interfaces among equipment in the RED area that
constitute a system may not be required to comply. In these cases, the
engineer must consider the technology used in the interface. Other than
EIA-RS-232C interfaces (see 5.3.3.1), interfaces having signal levels below 6
volts pose a low risk, while those above 6 volts should be afforded extra
safeguards, such as individually shielded pair cable and metallic race way or
conduit. Such measures should be taken, as indicated by instrumented TEMPEST
tests and analysis.
5.3.3.4 Low-risk technology. Some equipment may use laser and xerography
technologies to produce copies of classified information. That portion of
the device is inherently low risk due to the nonexistence of emanations. The
risk area is the electronics driving such equipment. If the electronics uses
technology at levels of 6 volts or less, a low risk may be achieved. (Consult
NACSIM 5100.)
5.3.3.5 Converted equipment. Equipment exists in the Department of Defense
(DoD) inventory that was procured with high-level components and subsequently
retrofitted for low-level operation. If such equipment is used in a system,
the designer is cautioned that some of this equipment was only partially
converted. Converters were installed in the signal lines, but no change was
made to the internal electronics. If converted equipment is used, it should
be separated as if it were a high-level device, unless it is known that all
electrical components were property converted.
5.3.3.6 Video devices. Equipment using cathode ray tube displays present a
source of free space emanations. Such devices may require shielding around
the display, particularly across the face of the display. Shielding glass
and metallic housings are commercially available to accomplish this
containment of emanations.
5.3.3.7 Magnetic disk memories. A common commercial installation practice
in systems with magnetic disk memories is to remove the cabinet sides of a
group of units and bolt the chassis together as a single unit. This practice
should be avoided as the arrangement negates the shielding effectiveness of
the cabinet. Each unit should be installed as a stand alone with separate
grounding and bonding.
5.3.3.8 BLACK equipment installed in RED areas. Certain operations require
installation of BLACK equipment in RED areas, such as emergency action
consoles in Command and Control facilities. In such cases, the BLACK
equipment will be separated from RED equipment by 3 feet (0.9m) if the BLACK
equipment is low level or 6 feet (1.8 m) if high level. However, BLACK voice
equipment will require 6 feet (1.8 m) separation regardless of the level.
(See 5.8 for other telephone requirements.) (See tables I and II.)
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