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 MIL-HDBK-232A
protection viewpoint, individually shielded pairs may not offer sufficient
increase of protection for the cost involved. As a matter of engineering
practice, cables should be sized to accommodate a single channel or a single
interface group between equipment.
5.7.2.2.2 Metallic wire ways. Metallic wire ways and conduits provide
shielding for cables contained therein. Separate wire ways and conduits are
used for RED and BLACK cables. Where such wire ways must run parallel,
separation should be as indicated in table I. Where RED and BLACK wire ways
must cross, crossings should be perpendicular. Wire ways should be unpainted
to provide electrical continuity, and all sections and covers firmly bonded,
grounded, and in place. In the REA, cables between equipment may be double
shielded if the volume makes wire ways impractical.
5.7.2.3 Fortuitous probes and other exploitation. Where emanations have
been reduced to acceptable levels, other exploitation schemes must be used by
hostile elements, such as taps or probes. Since probes may take on any form
through any conducting media ingressing or egressing a facility, controls
must be placed on all pipes, wire ways, conduits, and conductors.
5.7.2.3.1 Conductors. All signal and power lines ingressing and egressing a
facility should do so through a single cable and power entrance vault, with
access restricted. Further, an accounting of all conductors is necessary.
Most facilities are installed with extra conductors to accommodate upgrades.
All such conductors should be grounded at every DF. In no case should unused
conductors be crossconnected to conductors going to subsequent DFs. Spare
pairs which are in place between BEA and a CBEA to reroute circuits should be
grounded when not in use. This grounding provision can be provided in the
patch panels.
5.7.2.3.2 Pipes, conduits, and wire ways. In unshielded facilities, all
pipes, conduits, and wire ways should be equipped with a nonconductive
section at the point of egress of the LEA. The section internal to the LEA
should be bonded to the facility EESS. The section external to the LEA
should also be bonded to the EESS. In shielded facilities, all pipes,
conduits, and wire ways are circumferentially bonded to the facility entrance
plate. (NOTE: Ducting and piping for heating, ventilating, and
air-conditioning equipment receive the same treatment.)
5.7.2.3.3 Surveillance. All wire ways and conduits should be installed so
as to be in constant view except as follows:
a.
When passing through walls, floors, or ceilings in the CAA.
b.
When permanently installed within the walls, under the floors, or
above the ceiling provided that:
(1)
The condition of the installation is monitored.
Accessibility is
only from within the CAA or LEA.
(2)
Accessibility is only from within the CAA or LEA.
(3)
Requirements for a PDS are met.
(4)
Alarmed barriers to prevent undetected human penetrations are
provided.
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