(DBS) Direct Broadcast Satellite: A TV broadcast service from a small satellite dish antenna that offers similar services, like that of cable TV, and which transmits highly compressed digital signals.
(DCS) Digital Crossconnect System: A high-speed data channel switch that in response to dialing instructions independent of the data traveling through, switches transmission paths.
(DDD) Direct Distance Dialing: A switched service that allows for whomever originates a call to directly place long-distance calls without assistance.
(DDS) Digital Data Service: A synchronized digital service that interconnects digital transmission centers.
(DE) Discard Eligibility: An indicator in a frame relay that identifies which frames can be discarded in case of network congestion.
Descrambler: Electronic circuit that restores a scrambled video signal to its original form. Television signals, especially those transmitted by satellite, are often scrambled to protect
against theft and other unauthorized use.
Dialing Parity: The ability to reach a residential or business phone by dialing the same number of digits no matter which company’s network is used.
(DID) Direct Inward Dialing: A feature that allows calls to the ten-digit DID telephone number to reach that specific extension without human interference.
Digital: An intelligence-carrying signal consisting of a stream of bits of zeros and ones for sound, video, computer data or other information.
Digital Cable: Cable services, programming, and equipment that use digital, not analog, formats
(see DTV and HDTV).
Dish: A parabolic antenna used to receive satellite transmissions at home. The older “C band” dishes measure 7-12 feet in diameter, while the newer “Ku band” dishes used to receive high powered DBS services can be as small as 18 inches in diameter.
Distant Signal: Television signal from another city that is imported and carried locally by a cable television system.
(DLC) Digital Loop Carrier: The supplies and equipment that are used for digital multiplexing of telephone circuits. This would include the lines.
(DLCI) Data Link Connection Indicator: The number sequence that identifies public data networks.
(DMA) Designated Market Area: A television market as delineated by the A.C. Nielsen Company.
(DMT) Discrete Multitone Technology: A technology that uses digital signals to transmit multiple signals over the present pair of copper wiring.
(DN) Directory Number: A 10-digit number assigned by the local telephone provider. Generally referred to as an individual’s telephone number.
(DOCSIS) Data Over Cable Service Interface Specification: The leading standard for cable modems.
(DOD) Department of Defense: The United States federal agency overseeing the military.
Downstream: Flow of signals from a cable system’s headend through its distribution network to a customer.
(DQPSK) Differential Quadra Phase Shift Keying: A phase modulation technique used in modems to code relative changes of a carrier signal phase in the transmitted waveform.
Drop Cable: The final stretch of coaxial cable that connects a customer’s home to the cable system.
(DS-O) Digital Signal Level 0: A classification of digital circuits with a rate of transmission rate of 64 kb/s.
(DS-1) Digital Signal Level 1: The rate of transmission of a DS-1 (or T -1) is of 1 .544 Mb/s and 24 channels are associated with it.
(DS-3) Digital Signal Level 3: The rate of transmission of a DS-3 (or T -3) is of 44.736 Mb/s and is associated with 672 channels.
(DSC) Digital Selective Calling: A synchronous system that is used to set up contact by radio with a station or group of stations.
DSLAM: Digital Subscriber Line Access Multiplexer. A DSLAM is a network device used to connect multiple end-users/subscribers to a high speed Internet or backhaul connection.
Used by the LECs to provide DSL type services (data, video) over existing copper infrastructure. Originally located within a CO, the LECs have pushed DSLAMs further into the network to increase subscriber opportunity and provide robust services farther to the edge of the network.
(DSP) Digital Signal Processors: A special programmable device used for digital signal processing by providing ultra-fast instruction sequences.
(DSU) Data Service Unit: An apparatus used to link data terminal equipment to the carrier's digital services, such as T -1.
DTH (Direct-To-Home): All satellite service providers, including C-band and Ku band (DBS).
(DTMF) Dual Tone Multi-Frequency: A type of double-frequency audio signals that are generated by a push-button device like those on a touch-tone telephone.
DTV (Digital TV): Television signals transmitted and received in digital format (discontinuous zeroes and ones; compare with ANALOG). Digital TV has several formats and varying degrees of resolution, from 480 lines per screen progressively scanned to 1080 lines interlaced. DTV includes HDTV, but not all DTV is HDTV since the bandwidth required for HDTV can be broken down to accommodate several DTV signals of lesser resolution.
Dual Cable: Two wires or coaxial cables operating side-by-side to provide extra channel capacity and interactivity.
(DWDM) Dense Wavelength Division Multiplexing: A technique by which multiple light signals (generally using four or more signals) of different wavelengths, are simultaneously transmitted in the same direction over a single optical fiber.