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 MIL-HDBK-232A
BEA, LEA, or CAA should be grounded at both ends. Cables for equipment or
systems designed to operate in the high-level mode will be installed using
ferrous-type conduit with compression or threaded fittings or ferrous-type
cable duct. All RED signal and control lines, RED power, BLACK signal and
control lines, BLACK power, arid all lines which are not a part of the
communication system (door bells, administrative telephones, fire alarms,
etc.) should be encased in separate conduits or ducts. Physical separation
of all elements should be in accordance with table II. All conduits or ducts
that are in close proximity should be parallel. When crossovers are
necessary, all conduits or ducts should cross at right angles and with
appropriate physical separation. All junction or terminal boxes which are
part of a PDS used for TEMPEST control should be equipped with an
RFI-gasketed cover and must have all apertures closed by conduit or
ferrous-type aperture covers. All ducts should be grounded as indicated in
paragraph 5.6.1.2. Conduits, if properly installed with appropriate coupling
devices, will provide an adequate shield. All conduits and ducts should be
marked every 3 to 5 feet (0.9 to 1.5 m) to distinguish between RED and BLACK
runs. Normally, the less prevalent runs should be marked Wire lines that are
not a physical element of the information mission system will be identified,
BLACK. This includes utilities such as smoke detectors, thermostats, etc.
TEMPEST approved equipment which uses low-level balanced voltage digital
signaling, shielded cable, and has adequate built-in power and signal/control
line filters, may not require use of conduit or duct. As a minimum, however,
nonferrous shielded cable should be used. Use of conduit or duct is
dependent upon TEMPEST tests and local environment.
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