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 MIL-HDBK-232A
5.1.1.2.4 Internal RED/BLACK EM barrier. The internal EM barrier between
RED and BLACK equipment consists of several components:
a.
The physical separation between RED and BLACK equipment, power and
signal distribution facilities, and patch bays.
b.
Shielding of all signal cables.
c.
Encrypting or filtering all signal lines which connect RED and BLACK
equipment. All cable shields must be grounded to the equipotential
plane via a low impedance path at every convenient point.
5.1.1.2.5 Internal EM environmental barrier. The ambient EM environment in
most information processing facilities contains transients of sufficient
magnitude to disrupt the functioning of the processing equipment if allowed
to couple into the internal circuitry of the equipment. Consequently,
equipment is manufactured to provide some attenuation to such transients,
mostly at the point where external power enters the equipment. This built-in
protection is enhanced and expanded to provide a full barrier by providing a
closed shield for the equipment that is properly bonded to the equipotential
ground plane. The closed shield consists of the equipment case, metallic
power distribution facilities, and the required signal cable shield, all of
which must be circumferentially bonded together.
5.1.2 Facility design and layout. A sample layout of a medium-to-large
facility is shown in figure 16. Several principles to be used in laying out
any facility are summarized below.
5.1.2.1 Facility entry plate. Only one facility entry plate may be
installed. If more than one were installed, tremendous currents would flow
between them during a lightning strike or EMP, reducing the effectiveness of
the facility EM barrier. Therefore, the mechanical room should be located
adjacent to the EM vault, as shown in figure 16. These rooms should be
located at that portion of the building which is nearest to a good site for
the array of ground rods which must be driven into the earth to adequately
ground the entry plate.
5.1.2.2 Power conditioning room. This room contains the UPS or MG sets,
batteries for the UPS (one or more solid state online UPS), and the
switchgear, and therefore should be adjacent to the EM vault.
5.1.2.3 Main distribution frame (MDF). The MDF is the.point of entry for
signal cables into the technical area. The MDF should be located as near as
is practical to the EM vault.
5.1.2.4 Equipment areas. Based on connectivity considerations, BLACK
equipment is grouped together near the MDF, RED equipment is grouped together
some distance away (as dictated by separation requirements), and
crypto-equipment is located between the two. In many installations, there
may be more than one RED equipment area (REA), BLACK equipment area (BEA), or
crypto-area. The layout should group related equipment to minimize cable
length and therefore reduce the probability of emanations and pickup of
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