Demarc

(Pronounced "D-Marc") The demarcation point is the physical point at which the separation is made between the carrier's responsibilities for the circuit and those of the end user organization. The carrier is responsible for the local loop, which connects the user organization's premises to the carrier's CO (Central Office) or POP (Point of Presence) at the edge of the network. In a residential or small business application, the demarc is at the NIU (Network Interface Unit), which typically is on the side of the house or inside the garage. In a larger business application, it is at the MPOE (Minimum Point of Entry), which is the closest practical point to where the carrier facilities cross the property line or the closest practical point to where the carrier cabling enters a building. While the MPOE typically is in the form of a physical demarc, in older installations it may simply be in form of a tag hung on the entrance cable to identify a point of logical demarcation. There are exceptions. In some older Centrex installations in some states, the demarc is at the jack for each individual voice or data terminal. In some older campus environments, there may be a demarc for each of several cables coming from various directions, and the demarc may be well inside the property line. In either case, it is the responsibility of the carrier to install and maintain the local loop and the demarc device, which includes some form of protector against lightning and other electrical anomalies, and some form of intelligence to support loopback testing. It is the responsibility of the end user organization or building owner to install and maintain the inside cable and wire system, which typically terminates in the demarc through a plug-and-jack arrangement. A demarc for voice services might be in the form of a simple RJ-11C jack (one line or trunk) connection, an RJ-14C (two trunks), an RJ-21X (up to 25 trunks), or a 66-block. A demarc for data services typically supports an RJ-48 (used primarily with a T1 or a Primary Rate Interface) termination.