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 MIL-HDBK-232A
overall shielded cable containing both RED and BLACK lines. Avoid this
practice whenever possible. If RED and BLACK lines are contained in the same
cable inside the shelter, filters or isolators should be installed at the
point of egress from the shelter.
40.3 Digital and analog cables connected to patch panels. Digital and
analog cables should enter the patch panel cabinet by using methods that
would prevent the cables from running adjacent to or crossing each other.
This is effective in reducing the possibility of crosstalk.
40.4 Sensitive Compartmented Information (SCI) and non-Sensitive
Compartmented Information (non-SCI). Shelters which are certified for SCI
and non-SCI traffic should have patch panels which are isolated by
communities. Panels should be clearly identified to indicate the community.
Panels that employ a different wiring configuration and have unique patch
cords should be used in order to eliminate inadvertent patching from one to
the other.
40.5 Filters and isolators. External filters or isolators may be required
on RED and BLACK signal lines which are contained in the same multipair
cable. All signal and control lines should terminate inside the shelter.
Signal lines which penetrate the shelter skin should do so through filters or
isolators installed at the point of penetration. Filters installed in series
with built-in filters ma,v result in changing the operating characteristics
of the filler and could modify the bandpass frequency, reducing the desired
signal rejection. If equipment contains filters, optic isolators are
recommended at the point of egress.
40.6 External RED and BLACK signal and control lines. Some transportable
systems are designed to have RED signal and control lines which are external
to the shelter. Separate RED and BLACK cables with an overall nonferrous
shield should be used for signal and control lines with separate connectors
at the facility entrance plate. RED signal lines external to the shelter
should be kept at least 6 feet (1.8 m) from BLACK signal lines and all power
cables.
50. Power- and signal-line isolation. Power- and signal-line isolation for
transportable systems is dependent on the type of equipment used and the
shelter design.
50.1 Power-line, isolation. Most transportable shelters are not equipped
with separate power distribution panels for RED and BLACK equipment. Devices
that use the high-level mode of operation without adequate filter devices
should have power-line filters installed as near to the power distribution
panel as possible. Equipment that is TEMPEST approved, uses low-level
signaling, and has adequate power-line filters should not have external
filters installed. When external filters are used, RED and BLACK power lines
should be separated by at least 3 feet (0.9 m). Conduits, cable ducts, or
cable race ways should be used when possible to provide further isolation.
50.2 Signal-line isolation. RED and BLACK signal lines should not be
included in the same multipair cable. RED and BLACK lines should be
separated by at least 3 feet (0.9 m) throughout the shelter. Equipment that
operates in the high-level mode, and does not have adequate signal-line
filters should have external filters installed. Equipment that is TEMPEST
approved, operates in the low-level mode, and has adequate filters installed
should not require external filters or isolation devices.
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