Dark Fiber

Plain optical transmission capacity that the customer, rather than the telecommunications carrier, 'lights' with its own electronic and photonic devices for use in communications.

Declaratory Ruling

US: A ruling issued by the FCC in response to a petition submitted by a member of the public or on its own motion which is intended to terminate a controversy or remove uncertainty. [47 C.F.R. § 1.2]


Dedicated Short Range Communications (DSRC)

US: Wireless services operating in the 5.850-5.925 GHz band providing intelligent transportation services designed to improve highway safety and efficiency, including, e.g., traffic monitoring, traffic congestion detection, collision warning systems, travelers' alerts, automatic toll collection, control of access to parking lots, preemption of traffic lights by emergency vehicles, electronic license plates, and electronic inspection of moving trucks through data transmissions with roadside inspection facilities.

Deniable Charge

US: A charge that, if not paid, may result in the termination -- denial -- of the customer's local exchange service. Conversely, a non-deniable charge is a charge that will not result in the termination of the customer's basic service for non-payment, even though the particular service for which the charge has been levied, e.g., paging service, could be terminated.

Designated Market Areas (DMAs)

US: Television marketing areas designated by Nielsen Media Research using audience survey information from cable and non-cable households to determine the assignment of counties to local television markets. Nielsen determines what constitutes a separate market using a complex statistical formula based upon viewership and other factors. There are 210 DMAs delineated by Nielsen.

Dial Equipment Minutes Weighting (DEM)

US: A universal service assistance program created by the FCC in 1987 that subsidizes a portion of the local switching costs of smaller telephone companies based on the premise that such companies have higher local switching costs per line because they cannot take advantage of certain economies of scale.

The FCC's jurisdictional separations rules allocate local switching equipment costs between the inter-state and intra-state jurisdictions on the basis of each jurisdiction's relative number of dial equipment minutes (DEMS) of use. DEMS are the minutes of holding time of originating and terminating local dial switching equipment. For small LECs (with fewer than 50,000 access lines) the DEM is weighted to allocate additional costs to the inter-state jurisdiction.

Prior to universal service reforms brought about by the '96 Act, these costs were funded by those who pay switched access charges: the interexchange carriers and, ultimately, their customers. The National Exchange carrier Association (NECA) estimated the total subsidy resulting from DEM weighting for 1995 to be about $311million.

In its May 1997 Report & Order on universal service reform the FCC altered the recovery mechanism for local switching costs allocated to the inter-state jurisdiction, concluding that DEM weighting was an implicit subsidy and,

therefore, inconsistent with the requirements of the '96 Act. It replaced the local switching support that carriers had received through DEM weighting with explicit support from the new system of federal universal service support.

Thus, as of January 1, 1998, a carrier formerly eligible to use DEM weighting is no longer permitted to recover through access charges the portion of its local switching costs that are allocated to the inter-state jurisdiction via the DEM weighting assistance program. Instead, the carrier's local switching access charges will be set using measured inter-state DEM, and the portion of costs attributable to DEM weighting will be recovered from the new universal service support system.

Dialing Parity

Europe:Dialling parity exists when the same number of digits have to be dialed when accessing a service which is provided by different competing service providers

COM(96)590

US:A circumstance in which customers are afforded the ability to dial telephone numbers without the use of special access codes regardless of the competing telephone company they select as their service provider. A formal definition of dialing parity is contained in the '96 Act , meaning 'that a person that is not an affiliate of a local exchange carrier is able to provide telecommunications services in such a manner that customers have the ability to route automatically, without the use of any access code, their telecommunications to the telecommunications services provider of the customer's designation from among two or more telecommunications services providers (including such local exchange carrier).' [See also CI '96 Act Reference 0(3)(a)(39)]


Digital Audio Radio Service (DARS)

A service delivered via satellite nationwide that provides radio programming with compact disc sound quality capable of offering high quality radio signals to listeners who currently receive few terrestrial signals.


Digital Electronic Message Service (DEMS)

Terrestrial wireless point-to-multipoint microwave networks designed to communicate information between a fixed main station and a number of fixed user terminals, capable of providing competitive local telephone service, private local voice networks, Internet access, switched and dedicated data services, ISDN, frame relay, asynchronous transfer mode services, and video conferencing. The FCC licenses DEMS for both common carrier and private use and regulates them as fixed microwave services.

Digital Enhanced Cordless Telephony (DECT)

A cordless telephone system that enables fixed network operators to offer customers freedom of movement around the home.



 
 

Digital Subscriber Line (xDSL)

A network transmission technology that uses equipment connected to each end of a conventional copper telephone loop (subscriber line) to carry digital signals at comparatively high speeds. Depending on the technology used and the distance between the local exchange carrier switch and the customer's premises, DSL can expand existing subscriber line capacity by a factor of 50 or more, to speeds of up to 2.0 megabits per second, without additional engineering normally associated with the provision of such wideband transmission capacities.


DSL can be used to transmit interactive video to subscriber's premises and other applications requiring high transmission capacity. DSL also allows for the simultaneous transmission of both high-speed digital signals and an analog voice signal so that, for example, a computer and a telephone can operate on the same line and at the same time.

Because there are a variety of transmission speeds, techniques and vendor brands associated with DSL technology, each using the DSL suffix with a different prefix, DSL is referred to generically as xDSL (e.g., ADSL refers to asynchronous DSL, HDSL refers to high bit-rate DSL, VDSL refers to very high-speed DSL, etc.). [See also, Asynchronous Digital Subscriber Line]

Digital Subscriber Line Access Multiplexer(DSLAM)

A device (or function) included in the FCC's definition of packet switching which splits voice (low band) and data (high band) signals carried over a copper twisted pair (subscriber line), transmitting the voice signal to a circuit switch and the data signal to a packet switch, typically employing ATM (Asynchronous Transfer Mode) or IP (Internet Protocol). The DSLAM combines:
(1) the ability to terminate copper subscriber lines (which includes both a low-band voice channel and a high-band data channel, or solely a data channel);

(2) the ability to forward the voice channels, if present, to a circuit switch or multiple circuit switches;

(3) the ability to extract data units from the data channels on the subscriber lines; and

(4) the ability to combine data units from multiple subscriber lines onto one or more trunks that connect to a packet switch or packet switches.

Digital Television (DTV)

See 'advanced television services' (ATV) and 'high definition television' (HDTV) in this glossary.

Direct Broadcast Satellite Operator

A Multichannel Video Programming Distributor (MVPD) that downlinks programming from many different satellites pursuant to contracts with programmers, packages the programming into service offerings, and makes those service offerings available to subscribers over a proprietary facility.


DBS operators have a public interest obligation to reserve between 4% and 7% of their channel capacity for noncommercial programming. DBS subscribers generally use relatively small rooftop dishes (usually less than one meter in diameter) to receive the programming from the individual orbital location from which the DBS operator is transmitting the service. Both services and equipment are available to subscribers from a variety of retail outlets, including large national consumer electronics retailers.

Direct Broadcast Satellite Service

A radiocommunication service in which signals transmitted or retransmitted by satellite space stations are intended for direct reception by the general public, both individual reception and community reception. [47 CFR § 100.3]


Direct Inward Dialing (DID)

A local exchange carrier (LEC) service that can redirect calls in the telephone network and can be adapted to provide a form of service provider number portability. If a customer transfers his or her existing telephone number (NXX-XXXX) from carrier A to carrier B, any call to that customer is routed to the central office switch operated by carrier A that is designated by the NXX code of the customer's telephone number. Carrier A then routes the call over a dedicated facility to carrier B's switch. Carrier B then completes the routing of the call to its customer. The change in terminating carriers is transparent to the calling party.


Directory Assistance

A service that allows subscribers to retrieve the telephone numbers of other subscribers. (See also Directory Services and Non-local Directory Services.)

Directory Services

Services that include the publishing of telephone directories and the provision of directory assistance that allows telephone subscribers to retrieve the telephone numbers of other subscribers. (See also Directory Assistance and Non-local Directory Services

Direct-to-the-Home Satellite Service (DTH)

A satellite service in which programming is transmitted or broadcast by satellite directly to the subscribers' premises without the use of ground receiving or distribution equipment, except at the subscribers' premises or in the uplink process to the satellite. [See also CI '96 Act Reference II(205)(b); VI(602)(b)(1)]


Direct-Trunked Transport Service

Transport service is the component of interstate switched access service offered to interexchange carriers (IXCs) by local exchange carriers (LECs) corresponding to the transmission and switching of traffic between the LEC's end (switching) offices and the LEC's serving wire center (SWC) to which the IXC's point of presence (POP) is connected by entrance facilities. Incumbent LECs currently offer two types of interstate switched transport service, direct-trunked service and tandem-switched transport. In direct-trunked transport, calls are transported between the SWC and the end office by means of a direct trunk that does not pass through an intervening switch. To recover the costs of direct-trunked transport facilities, the FCC's Part 69 access charge rules require incumbent LECs to impose a flat-rate charge on IXCs.


DISCO I

DISCO I refers to the first 'Domestic International Satellite Consolidation Order' which was issued by the FCC in January of 1996 in which it adopted a new policy allowing all US-licensed satellites to offer both domestic and international service, including fixed satellite service ("FSS") systems, mobile satellite service ("MSS") systems, and direct-broadcast satellite service ("DBS") systems. [See also 'DISCO II']


DISCO II

DISCO II refers to the second 'Domestic International Satellite Consolidation Order.' In this proceeding, initiated in May 1996, the FCC sought to establish procedures for evaluating applications by users in the United States who seek authority to use foreign satellites (non-US-licensed satellites) for communications services to, from, or within the US. The FCC issued rules for this policy in November 1997 which are referred to as the 'effective competitive opportunities' test for satellites, or 'ECO-Sat.' [see also 'Effective Competitive Opportunities - Satellites' and 'DISCO I'] .


Dominant Carrier

A carrier that is found by the FCC to have market power (i.e., power to control prices). Dominant carriers are subject to Price Cap Regulation, have tariff notification periods of 14, 45 or 120 days' notice, are also required to file cost support data for above-cap and out-of-band tariff filings, and additional information for new service offerings. Dominant carriers must obtain prior FCC approval to construct a new line, to extend a line, or to acquire, lease or operate any line, as well as to discontinue, reduce or impair service. (see also non-dominant carrier)


Drop Pole

A subscriber drop is a cable connecting the premises of a cable TV subscriber to the cable distribution network via a 'tap' located on or near a distribution pole in the subscriber's neighborhood. In cases where it is necessary for the drop to cross a roadway, a pole, called a 'drop pole,' is placed on the side of the roadway opposite the cable tap and the drop is hung over the roadway suspended on the distribution pole and the drop pole. The cable then enters the subscriber's premises from the drop pole.