AT&T System 75 Wiring Diagram page 191

CHAPTER 3. EQUIPMENT ROOM DESIGN
Sizing 25-Pair and Multiple 25-Pair Station Cables
Use the scale of the floor plan to determine the approximate length of
each 25-pair station cable. The 25-pair station cables must be selected
and properly sized to make maximum use of the hardware at the
equipment room or satellite location.
When using 110-type hardware, use 25-pair B25A cables to connect
adapters directly to the equipment room cross-connect field or satellite
location. Staggered-finger cables, equipped with factory-installed 25-pair
connectors at both ends (male to female), are recommended for use
when multiple 25-pair cables are to be used between the equipment
room or satellite location and the adapters. B25A cables are required at
the equipment room or satellite location to connect the staggered-finger
cables to the 110-type terminal blocks.
When using 66-type hardware, use 25-pair A25B cables to connect
adapters directly to the equipment room cross-connect field or satellite
location. Staggered-finger 25-pair cables (double- or single-ended), are
recommended for use when multiple 25-pair cables are to be used
between the equipment room or satellite location and the adapters.
B25A cables are required at the equipment room or satellite location to
connect the double-ended (female to female) staggered-finger cables to
the 66-type connecting blocks.
Use the following information to determine the cable size (cable pairs)
required for either 3-pair or 4-pair circuits. Note the length and size on
the floor plan to aid in the ordering and installation of the station cables.
3-Pair Station Cable Circuits
To determine the size of station cables containing 3-pair circuits,
multiply the number of 3-pair circuits required at the satellite location by
3.5. Then, using the minimum size cable requirement, round up the
cable size requirement to the next highest available cable bundle size.
This will provide additional pairs for growth and compensate for the fact
that every twenty-fifth pair in a cable is not used.
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