Wired Broadband and Related Industry Glossary of Terms with Acronyms As of 13 June 2011 Compiled By: Conrad L. Young, Director, Broadband Technical Strategy

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The loss of power at a joint that occurs when the transmitting fiber has a diameter greater than the diameter of the receiving fiber. The loss occurs when coupling light from a source to fiber, from fiber to fiber, or from fiber to detector. [Fib111]

Diameter-mismatch Loss Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/d

Dichroic Filter

An optical filter that transmits light according to wavelength. Dichroic filters reflect light that they do not transmit. Used in bulk optics wavelength-division multiplexers. [Fib111]

A non-conductive insulator material between the center conductor and shield of coaxial cable.[Arr11] Also, any substance in which an electric field may be maintained with zero or near-zero power dissipation. This term usually refers to non-metallic materials. [Fib111]

DiffServ or DS
Differentiated Services Architecture for Network Traffic

Differential Gain

In color TV, the change in gain, expressed in dB, for the 3.58-MHz color sub- carrier as the level of the luminance signal is varied from blanking to white. A type of distortion in a video signal that causes the brightness information to be incorrectly interpreted. [Fib111]

Differential Phase

Variation in phase of the color sub-carrier of a TV signal as the level of the luminance signal is varied from blanking to white. A type of distortion in a video signal that causes the color information to be incorrectly interpreted. [Fib111]

Differentiated Services (DiffServ, or DS)

A protocol for specifying and controlling network traffic by class so that certain types of traffic get precedence—for example, voice traffic, which requires a relatively uninterrupted flow of data, might get precedence over other kinds of traffic. Differentiated Services is the most advanced method for managing traffic in terms of what is called Class of Service (CoS). Unlike the earlier mechanisms of 802.1p tagging and Type of Service (ToS), Differentiated Services avoids simple priority tagging and depends on more complex policy or rule statements to determine how to forward a given network packet. An analogy is made to travel services, in which a person can choose among different modes of travel—train, bus, airplane—degree of comfort, the number of stops on the route, standby status, the time of day or period of year for the trip, and so forth. For a given set of packet travel rules, a packet is given one of 64 possible forwarding behaviors—known as per hop behaviors (PHBs). A six-bit field, known as the Differentiated Services Code Point (DSCP), in the Internet Protocol (IP) header specifies the per hop behavior for a given flow of packets.

Diffraction Grating

An array of fine parallel equally spaced reflecting or transmitting lines that mutually enhance the effects of diffraction to concentrate the diffracted light in a few directions determined by the spacing of the lines and by the wavelength of the light. [Fib111]

Diffraction Grating Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/d

DIFL Levels
(1) In communications and computer technology, digital refers to a method of encoding information using a binary system made up of zeroes and ones. In communications technology this takes the form of two very different electrical voltages, several volts positive and negative, to represent the two values. This substantial difference in voltages for each state makes it unlikely that minor fluctuations in voltage due to electro-magnetic interference will change the way a signal is interpreted when received. (2) Information that is encoded into bits and bytes, or packets (0s and 1s, computer binary language). Generally perceived to be an advanced communication form offering clearer signals and increased transmission capacity.

Digital Signal Waveform courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/d

Digital Application Software Environment (DASE)
A standard by ATSC addressing interactive television.

Digital Audio Visual Council (DAVIC)

DAVIC is an international consortium working on the development of standards for interactive television.

Digital Certificate

A binding between an entity's public key and one or more attributes relating to its identity, also known as a public key certificate.

Digital Compression

An engineering technique for converting a cable TV signal into a digital format which may then be processed in a manner that requires a smaller portion of spectrum for its transmission. This compressed format allows many channels to be carried in the bandwidth normally required for one signal. This format can also be easily stored and manipulated.

Digital Enhanced Cordless Telecommunications (DECT)

A European standard governing panEuropean digital mobile telephony. Specified in DVB MHP as a type of return channel network interface for use in receiving and transmitting IP packets.

Digital Facility

A switching or transmission facility designed specifically to handle digital signals.

Digital Program Insertion (DPI)

The digital splicing of one Moving Pictures Experts Group (MPEG) program (typically a commercial) into another based on digital 'cues' within the MPEG transport stream.

Digital QAM

In digital QAM, the input stream is divided into groups of bits based on the number of modulation states used. For example, in 8QAM, each three bits of input, which provides eight values (0-7) alters the phase and amplitude of the carrier to derive eight unique modulation states. In 64QAM, each six bits generates 64 modulation states; in 128QAM, each seven bits generates 128 states, and so on. See modulation.

Digital Receiver Interface (DRI)

A CableLabs-specified interface over Internet Protocol (IP) that protects cable operators' "harm-to-service" issues. These issues include ensuring that information like emergency alerts and set-up screens are displayed, that there is sufficient bandwidth to deliver the service, that the content is not altered, etc. It also provides commands to enable communication of information between an OpenCable
unidirectional receiver (OCUR) and a home media server (HMS).

Digital Rights Interface Receiver (DRIR)
A more generic term [than home media server (HMS)] for the device on the downstream side of the DRI. This device receives protected digital content over the digital rights interface (DRI) interface and may store or present it according to license agreements with the cable operator. The home management system (HMS) has digital rights management (DRM) change-out, updating, and other requirements that the DRIR does not have.

Digital Receiver Interface Transceiver (DRIT)
A more generic term [than OpenCable™ unidirectional receiver (OCUR)] for the device on the upstream side of the digital rights interface (DRI). This device receives protected digital content from the cable plant that encodes it with an approved digital rights management (DRM) to distribute it over the digital rights interface (DRI). An OCUR has additional requirements around digital rights management (DRM) change-out, updating, and a few other things that a generic digital rights interface transceiver (DRIT) does not have.

Digital Rights Management (DRM) System
A coding system applied to digital content that manages the usage rights of that content. In order to present the content, the rights specified must be honored by the presenting device. This requirement is usually enforced by attaching the digital rights management (DRM) to encrypted content and protecting the information required to decode the content with keys that can only be obtained by a device authenticated by the DRM.

Digital Set-Top Box
A device which accepts digital encoded television broadcasts and converts them to display on an analog television set.

Digital Signal

A signal that has a limited number of discrete states prior to transmission. This may be contrasted with an analog signal which varies in a continuous manner and may be said to have an infinite number of states.

Digital Signature
A data value generated by a public-key algorithm based on the contents of a block of data and a private key, yielding an individualized cryptographic checksum.

Digital Speech Interpolation

DSI - A means of transmitting telephony. Two and One half to three times more efficiently based on the principle that people are talking only about 40% of the time. [Sat07]
Digital Storage Media-Command and Control (DSM-CC)
Syntax defined in the MPEG-2 standard, part 6, for VCR-like control over a bitstream. Playback commands include Still-Frame, Fast-Forward, Advance, and Goto.

Digital Subscriber Line (DSL)

High-speed technology to transfer data over an existing twisted-pair copper telephone line. Asynchronous technology (ADSL) provides data transmission rates up to 7 Mbps in one direction, generally within approximately three miles from a telephone central office. See also HDSL and VDSL.

Digital Subscriber Line Access Multiplexer (DSLAM)

A DSLAM is an xDSL line-interface device located in a telephone company Central Office. One side of a DSLAM connects to customer premises network interface devices (NIDs) over the local loop. The other side interfaces with the PSTN and a wide area (Frame Relay or ATM) network system.

Digital Transmission

A mode of transmission in which all information to be transmitted is first converted to digital form and then transmitted as a serial stream of pulses. Any signal-voice, data, television-can be converted to digital form.

Digital Transmission Licensing Administration (DTLA)
Licensing authority for DTCP, HDCP and 5C certificates.

Digital Video Broadcasting (DVB)

Digital video broadcasting is a European standard for digital television.

Digital Video Interface (DVI)

A specification created by the Digital Display Working Group (DDWG) to accommodate analog and digital monitors with a single connector. There are three different DVI configurations: DVI-A, designed for analog signals, DVI-D, designed for digital signals, and DVI-I (integrated), designed for both analog and digital signals.

Digital Video Recorder (DVR)

A consumer device which uses a hard disk drive to record television programs. Also provides pause of live television feature. See also PVR.

Digital Video Subcommittee (DVS)

An ANSI-sponsored standardization committee of the SCTE.


Download Info Indication


An electronic device that lets current flow in only one direction. Semiconductor diodes used in fiber optics contain a junction between regions of different doping. They include light emitters (LEDs and laser diodes) and detectors (photodiodes). [Fib111]
Diode Laser

Synonymous with injection laser diode. [Fib111]
Diplex Filter

The diplex filter isolates frequencies in both the downstream (DS) and upstream (US) in a cable industry HFC network allowing bi-directional signal transmission over the same coaxial cable. Also known as a diplexer. A diplexer is a passive device that implements frequency domain multiplexing. Two ports (e.g., L and H) are multiplexed onto a third port (e.g., S). The signals on ports L and H occupy disjoint frequency bands. Consequently, the signals on L and H can coexist on port S without interfering with each other. Typically, the signal on port L will occupy a single low frequency band and the signal on port H will occupy a higher frequency band. In that situation, the diplexer consists of a low pass filter connecting ports L and S and high pass filter connecting ports H and S. Ideally, all the signal power on port L is transferred to the S port and vice versa. All the signal power on port H is transferred to port S and vice versa. Ideally, the separation of the signals is complete. None of the low band signal is transferred from the S port to the H port. In the real world, some power will be lost, and some signal power will leak to the wrong port. The antenna is connected to the screw terminals to the left of center. The diplexer, being a passive device, is reciprocal: the device itself doesn't have a notion of input or output. The diplexer is a different device than a passive combiner or splitter. The ports of a diplexer are frequency selective; the ports of a combiner are not. There is also a power "loss" difference - a combiner takes all the power delivered to the S port and equally divides it between the A and B ports. A diplexer does not. A diplexer multiplexes two ports onto one port, but more than two ports may be multiplexed: a three-port to one-port multiplexer is known as a triplexer.
Typical diplex filter frequencies “splits” are as follows:

HFC Application:

Downstream (DS) Frequencies (MHz):

Upstream (US) Frequencies (MHz):

Guard Band (MHz):

North America HFC Cable Plants

52 to 750+

5 to 40


North America HFC Cable Plants

54 to 750+

5 to 42


North America HFC Plants

70 to 750+

5 to 55


European Union (EU) HFC Plants

85 to 870+

5 to 65


Japan HFC Cable Plants

88 to 550+

5 to 65


North America HFC Cable Plants (standard DOCSIS® 3.0 Frequency Plan)

88 to 750+

5 to 42


North America HFC N-Split

104 to 750+

5 to 85


North America HFC Cable Plants (DOCSIS® 3.0 Optional Frequency Plan)

108 to 750+

5 to 85


Link to Tutorial on the diplex filter: http://www.youtube.com/watch?v=Q1kLR4mWgt0&feature=related Source: Auriga USA LLC

Direct Broadcast Satellite (DBS)
Satellite technology that transmits directly to the end user or customer. DBS describes a frequency allocation and wide spacing between satellites that generally permits higher-powered transmissions through the air to small 18- to 24- inch receiving facilities located on customer premises (“point-to-multipoint” transport). Also known as direct-to-home (DTH) satellite or SATCOM-DBS.

Directional Coupler

A passive signal splitting device, with minimum signal loss between the input port and the output port (referred to as “through loss”), a specified coupling loss between the input port and the tap port (tap loss), and very high loss between the output port and tap port (isolation).[Arr11]

Excerpt from ANSI/SCTE 87-1 2008,

Graphic Symbols For Cable Systems Part 1: HFC Symbols

Directive Transmission
Directionally focused signal transmission from a base station to a remote user made possible by certain smart antenna systems with digital signal processing capabilities; these base stations use information obtained during reception to transmit signals selectively toward certain users and away from others.


The ratio of the optical power launched into an input port to the optical power returning to any other input port. Directivity has been referred to as near-end isolation or near-end crosstalk. [AOF11]

Directory Number (DN)
The number you dial to reach someone by telephone; a telephone number.

Software controls that allow a Windows program to manage video and sound hardware in a computer. It is usually used for multimedia in games or Web pages running under Windows 95/98 and Windows NT.

Discrete Stereo

A method of transmitting stereo in which the left and right channels are contained on completely separate subcarriers. To tune in this type of stereo, two completely separate subcarrier tuners are needed. The demodulator side of the deviation from a standard center frequency, the tuning frequency of the FM signal. [Cha07]

A type of FM demodulator used in satellite receivers. [Sat07]

See dish antenna or satellite antenna.

Dish Antenna
A high-gain antenna, shaped like a dish that is used for the transmission and reception of ultra-high-frequency and microwave signals.

Disk Operating System (DOS)
The basic term for software which controls a computer's operation and is loaded from some form of disk, usually a hard drive.


A term used to describe the chromatic or wavelength dependence of a parameter as opposed to the temporal dependence which is referred to as distortion. The term is used, for example, to describe the process by which an electromagnetic signal is distorted because the various wavelength components of that signal have different propagation characteristics. [Arr11]
Distant Signal
Broadcast TV signals which originate at a point too far away to be picked up by ordinary home reception equipment; also signals defined by the FCC as outside a broadcaster's license area. Cable systems are limited by FCC rules in the number of distant signals they can offer subscribers.

The departure, during transmission and amplification, of the received signal wave form from that of the original transmitted wave form.

Distortion, Harmonic

The result of nonlinearities in the communication channel that cause harmonics of the input frequencies to appear in the output. [Arr11]
Distortion, Linear (or Amplitude)

An unwanted change in signal amplitude so that the output signal envelope is not proportional to the input signal envelope, but no frequency related distortion is involved. [Arr11]
Distribution Amplifier

A high gain amplifier used to increase RF signal levels to overcome cable and flat losses encountered in signal distribution. [Arr11]
Distortion Level

The ratio, measured in dB, of distortion to desired carrier. [Arr11]

Distribution Hub
A location in a cable television network which performs the functions of a headend for customers in its immediate area, and which receives some or all of its television program material from a master headend in the same metropolitan or regional area.

Distribution Plant
The hardware of a cable system—amplifiers, trunk cable and feeder lines, attached to utility poles or fed through underground conduits like telephone and electric wires.

Distribution System

The part of a cable TV system consisting of trunk and feeder cables which are used to carry signals from the system head-end to subscriber terminals. Synonymous with trunk and feeder system. [Arr11]
Distribution System
The part of a cable television system used to carry signals from the headend to subscriber's receivers. Often applied, more narrowly, to the part of a cable television system starting at the bridger amplifiers.


The process of shifting the 6-MHz satellite-TV signal up and down the 36-MHz satellite transponder spectrum at a rate of 30 times per second (30 Hertz). The satellite signal is "dithered" to spread the transmission energy out over a band of frequencies far wider than a terrestrial common carrier microwave circuit operates within thereby minimizing the potential interference that any one single terrestrial microwave transmitter could possibly cause to the satellite transmission. [Sat07]

Digital Loop Carrier

Designated Market Area; geographic area defined by Nielsen Media Research Company as a group of counties that make up a particular television market. These counties comprise the major viewing audience for the television stations located in their particular metropolitan area. For the most part, the metropolitan areas correspond to the standard metropolitan statistical areas (see metro area) defined by the Federal Government Office of Management and Budget. The areas do not overlap, and every county in the United States belongs to only one DMA. DMAs are used in the evaluation of audience data as well as in the planning and buying of media. [All11]
A telephone company central office switch manufactured by Northern Telecom that has ISDN and other digital telephony capabilities. See also 5ESS.


Directory Number

Domain Name Server


Data Over Cable Service Interface Specification
The first version of the Data Over Cable Service Interface Specification. DOCSIS 1.0 defines requirements for cable modems and cable modem termination systems that enable broadband Internet access.

The ITU Telecommunication Standardization Sector (ITU-T) has approved the various versions of DOCSIS® as international standards. DOCSIS® 1.0 was ratified as ITU-T Recommendation J.112 Annex B (1998).

The second version of the DOCSIS protocol specification. DOCSIS 1.1 includes an enhanced Media Access Control (MAC)-layer that contains quality of service (QoS) traffic management functions as well as cable modem authentication extensions. Also known as “one-one”.

The ITU Telecommunication Standardization Sector (ITU-T) has approved the various versions of DOCSIS® as international standards. DOCSIS® 1.1 was ratified as ITU-T Recommendation J.112 Annex B (2001).

The third version of the DOCSIS protocol specification, developed to significantly increase the upstream data carrying capacity and the robustness to noise and interference. DOCSIS® 2.0 includes advanced TDMA and S-CDMA physical layer technologies.

The ITU Telecommunication Standardization Sector (ITU-T) has approved the various versions of DOCSIS® as international standards. DOCSIS® 2.0 was ratified as ITU-T Recommendation J.122.

DOCSIS® 2.0 + IPv6
The “DOCSIS® 2.0 + IPv6” standard (revision 3 published 10 February 2011) supports IPv6, which may require a DOCSIS® 2.0 equipment firmware upgrade on the customer premises equipment (CPE) (cable modem (CM)) side of DOCSIS® enabled networks.


DOCSIS® 3.0 features management over IPv6 and channel bonding, which enables multiple downstream and upstream channels to be used together at the same time by a single subscriber. [Cab11]

Common DOCSIS® 3.0 speeds are listed in the table below.

Channel configuration

Downstream throughput

Upstream throughput

Number of downstream channels

Number of upstream channels





171.52 (152) Mbit/s

222.48 (200) Mbit/s

122.88 (108) Mbit/s



343.04 (304) Mbit/s

444.96 (400) Mbit/s

122.88 (108) Mbit/s

The ITU Telecommunication Standardization Sector (ITU-T) has approved the various versions of DOCSIS® as international standards. DOCSIS® 3.0 was ratified as ITU-T Recommendation J.222 (J.222.0, J.222.1, J.222.2, J.222.3). DOCSIS® specifications may be found using this link: http://www.cablelabs.com/specifications/

DOCSIS Radio Frequency Interface (RFI) Specification
CableLabs radio-frequency interface specifications for high-speed data-over-cable systems. Also referred to as DRFI.


DePON is a unique PON offering that, for the first time, gives MSOs the ability to manage and operate EPON networks with their existing DOCSIS infrastructure. It preserves the existing investment in DOCSIS management, servers, applications and operations. Cable operators can use DePON to begin the migration to fiber-based networks while continuing to leverage existing DOCSIS and OSS operating procedures. Compared to existing and emerging HFC-based solutions, DePON systems increase bandwidth levels dramatically. DePON provides symmetrical capacity of up to 4Gbps per fiber feeder that can easily deliver the bandwidth-intensive applications that subscribers require. DePON enables cable operators to grow their customer base strategically when and where they have demand. DePON systems seamlessly coexist with existing DOCSIS-based systems and offer a strategic migration platform from HFC to FTTP. [Hit11]

PON Category:


Downstream (DS) Data Rates

Upstream (US) Data Rates


BPON (Broadband PON)

ITU-T G.983

622 Mbps

155 Mbps

RF Overlay using 1550nm optical λ

GPON (Gigabit PON) successor to BPON; provides for transport of asynchronous transfer mode (ATM), time division multiplexing (TDM) & Ethernet

ITU-T G.984

2.488 Gbps

1.244 Gbps

RF Overlay using 1550nm optical λ

EPON (Ethernet PON)

IEEE 802.3ah

100 Mbps

100 Mbps


GE-PON (Gigabit Ethernet PON)

IEEE 802.3ah

1 Gbps (std)

2.5 Gbps (dual speed)

1 Gbps (std)

1 Gbps (dual speed)


10GE-PON (10 Gigabit Ethernet PON)

IEEE 802.3av

10 Gbps

1 Gbps

RF Overlay using 1550nm optical λ

DOCSIS over EPON (DePON) – a combination of EPON & DOCSIS leveraging a cable operator’s DOCSIS network & OSSs (operational support systems). A DePON OLT looks & acts like a CMTS (cable modem termination system).


125 Mbps (32 passive optical split)

125 Mbps (32 passive optical split)

RF Overlay using 1550nm optical λ
DOCSIS 3.0 supports IPTV (internet protocol television)

RFoG (RF over Glass); associated with specific FTTP products & an emerging standard; RF is transmitted over fiber, instead of coaxial cable, through splitters to a node or R-ONT @ the premises; requires the addition of an EDFA (erbium doped fiber amplifier) & return receiver in the hub or headend (HE) to support bi-directional optical transport on a FTTH P2MP plant. Use of existing HE/hub CMTS, eQAM, &/or CMAP along with CPE is required.

SCTE 174 2010

160 Mbps (4-channel bonding)

160 Mbps (4-channel bonding)

DS RF Overlay using 1550nm & US RF Overlay using 1310nm or 1610nm optical λ
DOCSIS 3.0 supports IPTV (internet protocol television)

PON Categories as of 01 March 2011
DOCSIS® Variants

As frequency allocation band plans differ between U.S. and European CATV systems, DOCSIS® standards have been modified for use in Europe. These changes were published under the name of "EuroDOCSIS". The main differences account for differing TV channel bandwidths; European cable channels conform to PAL TV standards and are 8 MHz wide, whereas in North American cable channels conform to ATSC standards which specify 6 MHz. The wider bandwidth in EuroDOCSIS architectures permits more bandwidth to be allocated to the downstream data path (toward the user). EuroDOCSIS certification testing is executed by Excentis (formerly known as tComLabs), while DOCSIS® certification testing is executed by CableLabs. Typically, customer premises equipment receives "certification", while CMTS equipment receives "qualification". Most cable systems in Japan and Colombia utilize the North American version of DOCSIS®, while some employ a variant of DOCSIS® that uses upstream channels that are based on a 9.216 MHz master clock (as opposed to 10.24 MHz used in DOCSIS®/EuroDOCSIS) resulting in upstream channel widths that are a power-of-two division of 6 MHz (as opposed to 6.4 MHz in DOCSIS®/EuroDOCSIS).
Document Object Model (DOM)
An API for parsing a document and providing a view of the document by constructing a “tree” of objects in memory. The Document Object Model is a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content, structure and style of documents. The document can be further processed and the results of that processing can be incorporated back into the presented page.

Document Type Definition (DTD)
A formal grammar to specify the structure and permissible values of XML documents.

Dolby AC-3
Dolby AC-3 refers to the audio encoding format adopted by the ATSC for its advanced television audio encoding. Also known as Dolby digital.

Document Object Model

Domain Name Server (DNS)
A server that relates an Internet domain name (such as www.cablelabs.com) to an IP address.

Domain of an Application
The domain of an Xlet characterizes the space within which the Xlet is able to execute. This includes both the connection where the Xlet is delivered and other connections where an already executing Xlet is allowed to continue executing. An application cannot run outside its domain. The maximum lifetime of an application extends from the moment the user navigates to its domain until the moment that the user navigates away from its domain. In the broadcast case, a connection corresponds to a DVB-service. Broadcast signaling indicates which services can load an application and which services allow an already active application to continue.

Disk Operating System

Two rapid clicks of a personal computer (PC) primary (usually left) mouse button, usually performed to launch a program or open a file.

Down Conversion
The heterodyning of an input signal with the output of local oscillator, resulting in an intermediate frequency that is lower than the incoming signal frequency.


The circuit associated with a satellite receiver that lowers the high frequency signal to a lower, intermediate range. There are three distinct types of down conversion: single, dual and block. [Arr11]
Transmission of signals from a satellite to a dish or earth station.


The transfer of data from a remote computer, or server, to a local computer. To the Internet user, downloading means to request a copy of a file from another computer and then receive that file.

DownloadInfoIndication (DII)

A message that signals the modules that are part of a DSM-CC object carousel.


Flow of signals from the cable system control center through the distribution network to the customer. For communication purposes, associated with transmission (down) to the end-user. Or in cable television, the direction of transmission from the headend to the subscriber.


Digital Predistortion; A method of linearizing an amplifier to produce an amplified output sample, va, in response to a predistorted input sample, vd, derived from an input modulation sample vm, such that K times vm (K* vm), where K is the amplifier's desired constant amplitude gain, represents an amplifier’s output. [Cav91]
Digital Program Insertion

Dynamic Quality of Service


DOCSIS Radio Frequency Interface (RFI) Specification. CableLabs radio-frequency interface specifications for high-speed data-over-cable systems. Latest version DRFI specification is found using this link: http://www.cablelabs.com/cablemodem/specifications/d-rfi.html
Digital Receiver Interface


An instability in a preset voltage, frequency or other electronic circuit parameter. [Arr11]
Digital Rights Management

The cable and hardware from tap to subscriber is called the drop.

Drop Amplifier

An amplifier installed at subscriber location to provide RF signal adjustment (including gain, RF power level, and frequency tilt), RF signal splitting, and filtering as required to maintain acceptable operator network performance. Also referred to as a “house amplifier”.

Drop Cable
Generally 330 feet or less, of coaxial cable, starting at a tap and continuing on to the subscriber’s connection. Or coaxial cable that connects to a residence or service location from a directional coupler (tap) on the nearest coaxial feeder cable.

Drop Cable

In a cable TV system, the transmission cable from the distribution cable to a dwelling (i.e. RG59, RG6, RG7 or RG11). [Arr11]


Digital Signal Level 1. 24 Voice channels consisting of 64 kb per channel. Also referred to as T-1 (improperly). [Arr11]


DiffServe Code Point

DOCSIS Set-top Gateway. DSG is a CableLabs ® specification for transporting set-top box (STB) command and control information over Data Over Cable Service Interface Specifications (DOCSIS®). DSG defines interface requirements for transport of a class of service known as out-of-band (OOB) between a set-top network controller and digital STBs. Traditionally, physical transport of OOB messaging is carried over dedicated channels as defined by the Society of Cable Telecommunication Engineers Digital Video Subcommittee (SCTE DVS) 167 and SCTE DVS 178. Conditional access (CA), system information (SI), electronic program guide (EPG), emergency alert system (EAS), and other generic messages are sent from a headend controller to each STB via an RF carrier that is separate from the channels being watched—hence the term out of band. DSG moves away from traditional OOB transport, instead incorporating it into DOCSIS® digitally modulated carriers now used for cable modem service. DSG provides transparent uni-directional and bi-directional transport of OOB messaging over Internet Protocol (IP) between a cable modem termination system (CMTS) and STBs via a hybrid fiber coaxial network (HFC). DSG allows cable operators to combine cable modem and STB operations over one open, vendor-independent DOCSIS network, with no changes to the existing DOCSIS infrastructure. The DSG specification can be found at http://ww.opencable.com/downloads/specs/SP-DSG-I01-020228.pdf. A follow-up advanced mode specification is also in the works. [Cis04]


DOCSIS® Services ID
Digital Subscriber Line

Digital Subscriber Line Access Multiplexer

ISO/IEC Digital Storage Media-Command and Control

Digital Signal Processing

Digital Signature Standard

Digital Satellite System


Direct-Sequence Spread Spectrum; a telecommunications term with the following meanings:

  1. A system (a) for generating spread-spectrum transmissions by phase-modulating a sine wave pseudorandomly with a continuous string of pseudonoise code symbols, each of duration much smaller than a bit and (b) that may be time-gated, where the transmitter is keyed periodically or randomly within a specified time interval.

  2. A signal structuring technique utilizing a digital code sequence having a chip rate much higher than the information signal bit rate. Each information bit of a digital signal is transmitted as a pseudorandom sequence of chips.

Direct-sequence spread-spectrum transmissions multiply a "noise" signal to the data being transmitted. This noise signal is a pseudorandom sequence of 1 and -1 values, at a frequency much higher than that of the original signal, thereby spreading the energy of the original signal into a much wider band. The resulting signal resembles white noise, like an audio recording of "static", except that this noise can be filtered out at the receiving end to recover the original data, by again multiplying the same pseudorandom sequence to the received signal (because 1 × 1 = 1, and -1 × -1 = 1). As this description suggests, a plot of the transmitted waveform has a roughly bell-shaped envelope centered on the carrier frequency, just like a normal AM transmission, except that the added noise causes the distribution to be much wider than that of an AM transmission. By contrast, Frequency-hopping spread spectrum pseudo-randomly retunes the carrier, instead of adding pseudo-random noise to the data, which results in a uniform frequency distribution whose width is determined by the output range of the pseudo-random number generator. [Wor11]

Data Service Unit; A device used in digital transmission that adapts the physical interface on a DTE device to a transmission facility such as T1 or E1. The DSU is also responsible for such functions as signal timing. DSU is frequently coupled with a CSU (see above) as CSU/DSU. [Sat07]

Digital Terminal Adapter; A low-cost set-top box deployed by cable companies that provides digital service from the cable to analog TVs or digital TVs via the coax cable input. The digital terminal adapter (DTA) has only two coax cable connectors: in from the cable; out to the TV. It does not support a digital program guide or video-on-demand; however, it does display a brief name of the channel along with channel number on screen. The TV is set to channel 3 or 4, and channel changing is performed in the DTA. These devices were designed to reclaim analog channel space for more digital services. For example, Comcast claimed its 2009-2010 DTA deployment would enable it to replace 50 channels of analog spectrum with higher Internet speeds, more video-on-demand and up to 100 HD channels. Read more: http://www.answers.com/topic/dta-5001#ixzz1FXLlPGrt [Ans11]


Digital Transmission Content Protection

Digital Transmission Licensing Administration

Dual Tone Multi Frequency

Digital Television

Dual Cable
Two independent distribution systems operating side by side, providing double the channel capacity of a single cable.

Dual Polarization Feedhorn

An antenna feedhorn which can simultaneously receive both horizontally and vertically polarized satellite signals. [Arr11]

Dual Spin

Spacecraft design whereby the main body of the satellite is spun to provide altitude stabilization, and the antenna assembly is despun by means of a motor and bearing system in order to continually direct the antenna earthward. This dual-spin configuration thus serves to create a spin stabilized satellite. [Sat07]
Dual Tone Multi Frequency (DTMF)
Telephone “touch” tones. So-called because each keypad button pressed generates a unique combination of two audible tones or frequencies.

In a communications channel, the ability to transmit in both directions.

Duplex Transmission

Capability for simultaneous data transmission between a sending station and a receiving station. [Sat07]

Digital Video Broadcasting; The European-backed project to harmonize adoption of digital video. [Sat07]


DVB-C2 is a digital cable transmission system developed by the DVB Project. It uses the latest modulation and coding techniques to enable highly efficient use of cable networks where, up to now, in many cases downstream transmission capacity is already being used to its limit. DVB-C2 will initially be used for the delivery of innovative new services, such as video-on-demand (VOD) and high definition television (HDTV), helping digital operators to remain competitive and also to meet retransmission requirements; in the longer term the migration of current DVB-C services to DVB-C2 is also foreseen. DVB-C2 reuses some of the building blocks of other second generation DVB transmission systems - the “DVB Family” approach. The new standard was not required to be backwards compatible with DVB-C, although DVB-C2 receivers will be able to also handle DVB-C services. April 2010 saw the publication of the DVB-C2 specification (EN302769. An updated version is already available as DVB BlueBook A138 and the Implementation Guidelines Document (DVB BlueBook A147). In the same month, the Technical University of Braunschweig performed the first live DVB-C2 transmission, which validated the strong expected performance boost of the new system. The first DVB-C2 tuners are expected mid-2011.
Table comparing available modes and features in DVB-C and DVB-C2




Input Interface

Single Transport Stream (TS)

Multiple Transport Stream and Generic Stream Encapsulation (GSE)


Constant coding and modulation

Variable Coding & Modulation and Adaptive Coding & Modulation


[[Reed-Solomon error correction (RS)]]




Bit- Time- and Frequency-Interleaving


Single Carrier QAM




Scattered and Continual Pilots

Guard Interval


1/64 or 1/128

Modulation Schemes

16 to 256-QAM

16 to 4096-QAM


DVB Network
A DVB-network is a collection of MPEG-2 Transport Stream multiplexes transmitted on a single delivery system. For example, all digital channels on a specific cable system make up a DVB network.

DVB-J refers to the Java platform as defined as part of the DVB-MHP 1.0.1 [9]. For the OCAP 1.0 implementation, DVB-J is part of the execution engine.

DVB-J API refers to one of the Java APIs standardized as part of the DVB-MHP 1.0.1 [9]. For the OCAP 1.0 implementation, the DVB-J APIs are supported in the execution engine.

DVB-J Application
A DVB-J application is a set of DBV-J classes that operate together and need to be signaled as a single instance to the application manager so that it is aware of its existence and can control its lifetime through a lifecycle interface. DVB-J applications as specified by the DVB-MHP 1.0.1 [9] are not directly supported by OCAP 1.0 without modifications pertaining to this specification.

Digital Video Interface


Digital voltmeter; a device similar to a VOM that displays measured parameters in numeric form, typically using LCDs. Also known as a DDM (digital multimeter). [Arr11]

Digital Video Recorder

Digital Video Subcommittee

Dense Wavelength Division Multiplexing

Dynamic Host Configuration Protocol (DHCP)
An Internet protocol used for dynamically assigning network layer (Internet Protocol) addresses to IP hosts.

Dynamic Range

The dynamic range of an amplifier or mixer represents the range of signal levels over which it will exhibit its intended signal-processing properties. The lower limit of dynamic range is determined by the noise figure (NF) or sensitivity, while the upper limit is determined by the allowable level of signal distortion.[Ste89]



Electro-Absorptive Modulator; a semiconductor device which can be used for controlling (modulating) the intensity of a laser beam via an electric voltage. Its principle of operation is based on the Franz–Keldysh effect [1,2], i.e., a change in the absorption spectrum caused by an applied electric field, which changes the bandgap energy (thus the photon energy of an absorption edge) but usually does not involve the excitation of carriers by the electric field. Most electroabsorption modulators are made in the form of a waveguide with electrodes for applying an electric field in a direction perpendicular to the modulated light beam. For achieving a high extinction ratio, one usually exploits the quantum-confined Stark effect in a quantum well structure. Compared with electro-optic modulators (EOMs), electroabsorption modulators can operate with much lower voltages (a few volts instead of hundreds of thousands of volts). They can be operated at very high speed; a modulation bandwidth of tens of gigahertz can be achieved, which makes these devices useful for optical fiber communications. A convenient feature is that an electroabsorption modulator can be integrated with a distributed feedback laser diode on a single chip to form a data transmitter in the form of a photonic integrated circuit. Compared with direct modulation of the laser diode, a higher bandwidth and reduced chirp can be obtained. [Enc11]

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