Extensive Definition
In telephony, the demarcation
point is the point at which the telephone
company network ends and connects with the wiring at the
customer premises. A demarcation point is also referred to as the
demarc, DMARC, MPOE, or minimum point of entry.
History
Prior to the Bell System divestiture on January 1, 1984, American Telephone & Telegraph Company (AT&T) through its Bell System companies held a natural monopoly for telephone service within the United States. AT&T owned the local loop, including the telephone wiring within the customer premises and the customer telephone equipment. A similar arrangement existed with smaller, regional telephone companies such as GTE. As a result of deregulation of the telephone system, unbundling of the local loop, and lawsuits by companies wishing to sell third-party equipment to connect to the telephone network, there was a need to delineate the portion of the network which was owned by the customer and the portion owned by the telephone company or the common carrier. Where the portions meet is called the demarcation point.Equipment
The demarcation point varies from building type and service level. In its simplest form, the demarcation point is a junction block where telephone extensions join to connect to the network. This junction block usually includes a lightning arrestor (which requires a wire to earth ground.) In multi-line installations such as businesses or apartment buildings, the demarcation point may be a punch-down block. In most places this hardware existed before deregulation.In the United States, the modern demarcation
point is a device defined by
FCC rules (47 C.F.R. Part 68) to allow safe connection of
third-party telephone Customer-premises
equipment and wiring to the
Public Switched Telephone Network (PSTN). It is a square,
weatherproof housing which contains the wiring junction. It is
usually placed for easy access by a technician. It also contains a
lightning arrestor, fuse
and test circuitry which allows the carrier to remotely test
whether a wiring fault lies in the customer premises or in the
carrier wiring, without requiring a technician at the premises. The
demarcation point has a user accessible RJ-11 jack and small
loop of telephone cord connecting to the jack by a modular
connector. When the loop is disconnected, the on-premises
wiring is isolated from the telephone network and the customer
may directly connect a telephone to the network via the jack to
assist in determining the location of a wiring fault. In most
cases, everything from the central
office to and including the demarcation point is owned by the
carrier and everything past it is owned by the property
owner.
As the local loop becomes upgraded, with fiber optic
and coaxial
cable technologies sometimes replacing the original unshielded
twisted pair to the premises, the demarcation point has grown
to incorporate the equipment necessary to interface the original
premises POTS
wiring and equipment to the new communication channel.
References
See also
demark in German: Abschlusspunkt
Linientechnik
demark in Dutch: ISRA