Voice Over IP

THE LOCAL LOOP

As depicted in Figure A-1, the line connecting a telephone to the telephone service provider—the central office (CO), consists of two wires. The connecting point between the CPE and CO is called the point of demarcation and is usually found in a box (the protection block or station block) on the outside of a house. The outside plant facilities include the wires and supporting hardware to the CO.

At the CO, the lines enter through a cable room (aerial lines) or a cable vault (buried lines). The lines are then spliced to tip cables and directed to the main distribution frame (MDF); each wire is attached to a connector at the MDF.^[1] From the MDF, the wires are directed to other equipment such as a switch.

^[1] Even though the MDF ...