Quantcast Signal Reference Subsystem - hdbk419a_vol20279

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connected from the grounding electrode or bus of the main (first) service disconnect power panel to each case
of all equipments in the LEA and Controlled Access Area (CAA) (see Figure 1-69). The green wire protective
grounding feeder has no TEMPEST connotations or engineering techniques nor relationship with or part of the
signal reference subsystem.
2.4.4 Signal Reference Subsystem. Under the old RED/BLACK criteria, the signal reference subsystem was
called the signal ground system and was made up of those elements which permitted all station signals to be
electrically referenced to a single-point (see Figure 2-17). The old signal ground system was made up of the
following sub-sections:
Signal Ground Point. The signal ground point was the single point to which the RED and BLACK
signal ground conductors (installed throughout controlled access areas) were connected.
Signal Ground Reference Point.  In large facilities, several LEA's may have required multiple
RED/BLACK signal ground conductor feeders and connections to the signal ground point. To reduce the number
of connections to the actual signal ground point, a signal ground reference point may be established to provide
flexibility within the confines of the CAA or LEA for a facility containing multiple LEA's. A single signal
ground reference point may have been used for both RED and BLACK conductors, however in many instances
separate RED and BLACK signal ground reference points may also have been used. They should have been
located at a point central to all LEA's within a CAA or LEA. The location of the signal ground reference point
should have also been planned to provide the most direct connection to the signal ground point or earth
electrode subsystem.
Signal Ground Plane. A ground focal point for connection of the nonferrous shields and the common
of power supplies was usually a copper bus insulated from, but installed in, on, or near the Main Distribution
Frame (MDF), Intermediate Distribution Frame (IDF), or RED Intermediate Distribution Frame (RED IDF). The
signal ground plane would be connected to the signal ground point, or signal ground reference point via a heavy,
insulated wire (signal ground conductor) which was installed in metallic distribution facilities, and was at least
1/0 AWG.  Signal ground planes regardless of system designation (RED, BLACK), were not directly
interconnected to each other via signal ground conductors. The signal ground planes were common to each
other only at the point where the separate RED and BLACK signal ground conductors ultimately made
connection to the signal ground point or signal ground reference point.
Signal Ground Reference Plane. A common connection point was established to terminate either
RED or BLACK (not both together) equipment circuitry such as digital communication equipment or digital
terminal equipment. The signal ground reference plane was isolated from the ac protection ground or grounding
conductor or bus. When used, signal ground reference planes were connected to the nearest appropriate signal
ground plane.
Signal Ground Bus.  A ground bus found in the MDF, IDF, or CDF served as the ground system
connection point for the nonferrous shields of the signal and control cables.  The shield ground bus was
established and installed behind all vertical and horizontal terminal blocks in the distribution frames. The
shield ground bus system was made up of rows of strapped (#22 AWG) terminals terminating the nonferrous


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