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10. lNSTALLATlON EXAMPLE: DEFINITY GENERIC 2
WITH UNIVERSAL MODULES
This chapter illustrates the design process for a hypothetical main distribution frame (MDF) using a
seven-module system. The process consists of two steps: sizing the MDF and constructing the MDF.
SIZING THE MDF
Sizing is the determination of the number of 300-pair terminal blocks needed to construct the MDF.
First, assess the requirements of the four principle fields. Second, determine the number of blocks
needed for each field to meet those requirements.
For large installations, be especially aware of potential problems of expansion. Keep module ports in
the same area and use the closest available space for additions; leave space on the wall fields for carrier
additions even if the initial design does not require the use of all three available carriers.
Assessing Field Requirements
The four principal fields on the MDF are the network services central office (CO) trunks, auxiliary and
miscellaneous, equipment ports, and distribution fields. Following are the requirements for each field.
●
The network services field is where the CO cables terminate; it has green labels. For this installation
all trunks are digital. There is a direct connection between the customer’s channel service unit
(CSU) and the digital service 1 (DS1) interface of the telephone company. No cables have to be
terminated on this field, which eliminates the need for terminal blocks.
●
The auxiliary and miscellaneous field, which uses yellow labels, is where the cables from the
auxiliary equipment terminate. Two auxiliary cabinets, whose contents are unknown, serve this
system. Allow for the termination of twelve 25-pair cables from each cabinet.
In addition, a maximum of twelve 25-pair cables from the common control cabinet terminate on this
field. This includes the cabling for one attendant console.
●
The equipment port field, which uses purple labels, is where the cable from the equipment ports
terminate. There are 57 port carriers in the system and 10 DS1/MFAT carriers used to hold ANN15
(RGI) circuit packs. Modules 00 and 02 contain only 6 port carriers each. The remaining 5 modules
contain 9 port carriers and 2 DS1/MFAT carriers each.
●
The distribution field, which uses white labels, is where the distribution cables that run to the IDFs
terminate. Numerous factors affect the sizing of the distribution cable, including the stations served
by closets, the number and type of stations, the spares needed, and the possibility of cable breakage.
Allow for the termination of 14,000 distribution cable pairs.
10-1