| UNIT 3: INSTALLATION - LESSON 4: CO AND LINE EXTENSION CONNECTIONS Extension Connections An extension cable will need to be run from the location of the MDF to the location of each telephone. This style of cabling is often referred to as "home run cabling." The most common type of cable used today is 4-pair, Category 3. (Although only 2-pairs of wire are required to operate the proprietary telephones, most installers run 4 pair cable to allow for spare pairs.) As with any installation or construction project, local laws, building and electrical codes, and other regulations should always be observed, and the proper cable should be determined by local regulations. Many different techniques can be used to terminate extension cabling. Here are a few of the more commonly used methods. One easy method is to run Category 3 cables from the MDF to the location of each telephone. Then terminate both ends of the cable in an RJ-14 jack. This method is best suited for smaller installations that don’t require many extensions. Another method is to terminate the MDF side of the cable onto pre-wired 66M1-50 Blocks that have 4-wire modular jacks built in, while terminating the other end in an RJ-14 jack. This method requires less space at the MDF and also produces a cleaner installation. A third method involves using a 19’’ data rack and the optional KX-A244X Rack Mount Bracket. The MDF side of the cables can be terminated onto a Field Configurable Patch Panel utilizing 4-pin snap in jacks, while the other end is terminated in an RJ-14 jack. This method allows the Main Unit and extension terminations to share the same rack. The number of required extensions will often determine the best method for a particular installation. Other items to consider before selecting the termination method include, system expansion, extension relocation and system troubleshooting. Regardless of what method is used, all the extension cables should be terminated to provide a 4 -pin modular connection on both ends of all cable runs. The connections on both ends should follow the standard USOC wire scheme.
Cable Wire | Modular Jack Terminal
White-Blue | Green
Blue-White | Red
White-Orange | Black
Orange-White | Yellow
Note: Only connect the white-blue pair on the MDF side when only a single line extension will be used on an HLC4 or SLC8 card. After all the station cables have been terminated, the connections between the extension jacks on the Main Unit and the modular jacks on the MDF must be made. This is accomplished by interconnecting the two using 4-wire modular line cords. Connect a 4-wire modular line cord between the first hybrid port of the Main Unit and the first jack on the MDF. Route the line cord down and out the bottom of the Main Unit, then over to the MDF. Continue to run the line cords from the second hybrid extension jack to the second modular jack and so on, until all extensions are connected. Use the cable strap provided to bundle the cables for each card individually. We will use the main cable strap to secure all the cable bundles within the Main Unit later.