Demarc Point Extension
A demarc point extension, or demarc extension, or demarcation point extension, is the transmission path originating from the interface of the access provider's side of a telecommunications circuit demarcation point within a premise and ending at the termination point prior to the interface of the edge Customer Premises Equipment (CPE). This may include in-segment equipment, media converters and patch cords as required to complete the circuit's transmission path to the edge CPE.
A demarc extension may also be referred to as inside wiring, extended demarc, circuit extension, CPE cabling and riser cabling.
Demarc Point Extension Diagram

History of the Demarc Extension
A demarc extension became an important factor to consider in a building's telecommunications infrastructure after the 1984 deregulation of AT&T as well as the supplemental FCC rulings of 1991, 1996 and 1997. Preceding these rulings, the Bell System Companies held a monopoly and did not allow an interconnection with third party equipment. The incumbent local exchange carriers (ILEC) and other local access providers are now mandated by federal law to provide a point where the operational control or ownership changes. This separation between the local access provider and the end user/subscriber is called the demarcation point within a facility (typically a short distance from the minimum point of entry). This then becomes the responsibility of the end user to extend their service to the CPE location within a facility to provide connectivity for service, requiring a demarc extension.
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