NEC nd-20292 Main Distribution Frame MD!? consists of two, Parallel, Practice generally results

ND-20292

CHAPTER 2

APRIL, 1990

which could cause a hazard to personnel or to the proper functioning of the equipment.

D. Heat and humidity must be within the limits provided in Section 220.13 of this document.

E. Although its virtually noiseless operation allows a wide selection of installation sites, care should be taken that CCU(s) do not present a hazard to office traffic. For purposes of economy a central location to minimize cabling is often used.

230.5MDF CONSTRUCTION

The Main Distribution Frame (MD!?) consists of two

different types of standard quick-connect terminal blocks, which are to be mounted onto the 3/4” plywood backboard. For the sake of neatness and ease of access, it is also recommended that the blocks be mounted on appropriate standoffs. The recommended blocks are; the 66B50 type, for termination of the CCU J cables,

and the 66M50 type, for termination of the station cables.

The Intermediate Distribution Frame (IDF) requires only the 66M50 type blocks.

Both the MDF and the IDF utilize standard bridging clips for each type terminal block. The bridging clips are used to mate the left half of the terminal block (terminated cable run) to the right half of the terminal block (cross connection wire). The bridging clips are also useful during trouble shooting to help isolate the

cable runs and terminals/telephones from the central equipment and the Central Office Network from the system.

Refer to Figure 200-7 for a suggested MDF layout. Refer to Section 240 of this document for CCU wall mounting.

230.6CCU CABLES

Each CCU is equipped with three 50 pin, female

amphenol type connectors. These connectors are designated Jl to 53. Since each CCU uses the same designations for the J connectors, it is recommended that the MDF terminal blocks be labeled with the CCU number as well as the connector number; for example: lJ1,2Jl, 351,451,152, etc.

230.7 OUTSIDE LINES

A. The FCC authorized connector for the connection of

CO lines is an RJZlX. The CO lines will be connected in sequence within this termination block. Therefore, the lines must be ordered in the appearance order best suited to the customer’s usage.

66B50	66M50	TELCO
TYPE	TYPE	RJ2lX

Basic

I ecu I

Figure 200-7 Typical Full MDF Layout

B. Table 200-16 provides complete information about the 50 position connector, showing pin number, lead function, running cable color, and circuit designation.

C. Ground start and/or Loop start, loop dial DID, 2 and 4 wire E&M Tie lines (types I and V) can be connected to this system. It is recommended that only twisted pair wiring be used to cross connect the lines from the RJ2lX termination block to the MDF. Refer to Table 200-16 for proper connection identification.

D. HALF-TAPPING	or		PARALLEL
CONNECTIONS	MUST NOT		be used on outside
lines connected to the Electra		Mark11		System. This
practice generally results in		system		malfunctions
on the outside	lines.

E. Table 200-16 includes termination of PT and PR

designations, for the Power Failure Transfer feature. Cross connection between a CO tip (T) and ring (R) and an SLI-EB ETUs PT and PR, provides power failure transfer to a Single Line Telephone installed within the system.

230.8 STATION EQUIPMENT

A. When connecting Multiline Terminals, DSS/BLF Consoles, or CO Add-On Modules to the MDF, or IDF, individually twisted two pair cabling must be used.

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