| UNIT 3: INSTALLATION - LESSON 4: CO AND LINE EXTENSION CONNECTIONS CO Line Connections Before any CO lines are connected, Central Office Line Protection should be installed between the telephone company demarcation point and the Main Unit. This prevents the Main Unit from damage caused by overcurrent conditions, voltage spikes, and other transient voltages. Manufacturers of this type of equipment use different approaches to interfacing the Central Office lines to their equipment. Some use a connecting block like a 66 Block on which the Central Office lines are connected or "punched down" on specific terminals. Others use a modular approach that requires the two wires or "tip and ring" for each CO line be connected to screw terminals. Consult your Central Office line protection equipment documentation for more information. A separate RJ-11 jack should be installed for each CO line that will be connected to the Main Unit. Be sure to label and test each jack before connecting it to the Main Unit. Connect the Central Office lines to the Central Office line protection and to the Main Unit by connecting a 4-pin modular line cord between each of the RJ-11 jacks and the CO Line jacks of the Main Unit. Route the line cords down and out the bottom of the Main Unit and then over to the RJ-11 jacks of the Central Office line protectors. Be sure to clearly label both ends of all line cords when finished. This will allow you to easily identify and troubleshoot the CO lines in the future. Use the cable strap provided or similar cable ties to bundle the cables for each card individually. Later we will use the Main Cable Strap to secure all the cable bundles within the Main Unit.