Avaya 6424D+M User Manual page 34

MDF/lDF DESIGN: SYSTEM 85 AND DEFINITY GENERIC 2 WITH TRADITIONAL MODULES
Two factors govern the size of the MDF: the number of cable pairs to be terminated and the type of
cross-connect hardware used. Since the recommended cross-connect hardware for System 85 and
DEFINITY Generic 2 traditional system is the 110A, you only need to calculate the number of cable
pairs that must terminate on the MDF and calculate the number of 110A cross-connect blocks needed to
terminate those pairs to arrive at the size of the MDF.
This section helps you calculate the number of cable pairs terminating at the MDF by determining what
effect the four major fields of the MDF have on its size. These four fields are as follows:
Network services (CO trunks) field with green labels
Auxiliary equipment and miscellaneous field with yellow labels
Equipment (switch) port field with purple labels
Distribution field with white labels
A fifth field, with blue labels, may be required for some installations. It terminates 4-pair insulation
cables that connect the MDF directly to the IOs at the workstations.
The guidelines for sizing each field follow.
Network Services (CO Trunks) Field
The network services field, which uses green labels, is where the cabling from the CO terminates.
Cabling for analog network services is cross-connected to the green field from an RJ21X or an RJ2GX
interface. This cabling requires sneak-current protection in addition to the standard electrical protection
that the telephone company provides.
The total number of pairs in the network services cable is governed by the number of pairs that the
customer needs to connect to the network. It is also governed by the number of pairs that the telephone
company supplies . For example, if the customer needs to connect 750 pairs to the network, and the
telephone company supplies a 900-pair cable, the green field must be sized to terminate 900 pairs. All
900 pairs require protection.
For some installations, digital signal level-l (DS1) transmission capabilities also may be needed. When
the DS1 connection is part of the installation, then a digital signal cross-connect (DSX) may be required.
If a DSX is required, use the 800-series DSX as described in 800-Series DSX — General Description,
DSX Systems (365-301-102).
Auxiliary Equipment and Miscellaneous Field
The auxiliary field, which uses yellow labels, is where the cables terminate from auxiliary
equipment. This includes emergency transfer units, recorded announcement units, recorded dictation
units, loudspeaker paging-units, and radio-paging units. The auxiliary field also accommodates
miscellaneous cabling that is not associated with ports, such as cables from common control (CC)
cabinets, console cables, and alarm cables. Therefore, the size of the yellow field varies depending on
the amount of auxiliary equipment installed and the number of miscellaneous cables terminated.
Allocate space on the yellow field for the termination of a minimum of 300 pairs. Allocate additional
space in 300-pair groups for each auxiliary cabinet installed with the system. Increase the field size
2-11