The Cable Center

This glossary of cable and telecommunications terms is intended to enhance your understanding of this dynamic industry. We are able to present this information with the generous help of CableLabs - consult their website for the most up-to-date information about cable technology.

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Cable Loss
Defines the amount of cable loss that an amplifier is aligned (pre-equalized) through during factory alignment. Aligning an amplifier through cable creates a tilted gain response.

Cable Modem (CM)
A modulator-demodulator at subscriber locations intended for use in conveying data communications on a cable television system. Cable Modems offer a very high speed connection to the Internet, up to 30Megabits per second (several hundred times the speed of a 56Kbps modem). Technically speaking, though, a cable modem is not a modem at all, but a broadband network bridge.

Cable Modem to CPE Interface (CMCI)
The part of the DOCSIS specification defining the communication between the cable modem and consumer premise equipment (CPE) devices.

Cable Modem Termination System (CMTS)
Located at the cable television system headend or distribution hub, a CMTS provides complementary functionality to the cable modems to enable data connectivity to a wide-area network.

Cable Modem Termination System – Network Side Interface (CMTS-NSI)
The interface between a CMTS and the equipment on its network side.

Cable Network
Refers to the cable television plant that would typically be used for data over cable services. Such plants generally employ a downstream path in the range of 54 MHz on the low end to a high end in the 440 to 750 MHz range and an upstream path in the range of 5 to 42 MHz. Customers share a common communication path for upstream and a separate common path for downstream (i.e., effectively a pair of unidirectional buses).

Cable Powered
Devices obtaining a/c. power simultaneously with RF on the coaxial cable.

Cable Powering
A method of supplying power to solid-state cable television equipment by using the coaxial cable to carry both signal and power simultaneously.

Cable System
Facility that provides cable service in a given geographic area, comprised of one or more headends.

CableCARD
A removable security module (in a PCMCIA or PC card form factor) which, when inserted in an OpenCable certified set-top, television or other device, enables delivery of digital video programming and other services. The OpenCable specification is designed in part to support the retail sale of advanced digital set-top boxes and other devices. CableCARDs will be provided directly by the cable operator to customers who request them. Or a CableCARD is a detachable device, distributed by cable providers, that connects to the home receiver. The interface between the CableCARD unit and the receiver is specified by the OpenCable platform. CableCARD functionality includes copy protection and signal demodulation.

CableSCAN
A software product developed by TapSCAN which tabulated Nielsen household and demographic data for cable.

Cable Television Relay Services (CARS)
Terrestrial microwave frequency band used to relay television, FM radio, cablecasting and other signals from the original reception site to the headend terminal for distribution over cable.

Cable Termination
RF frequency signals travelling in coaxial cable will reflect off any impedance that does not match the 75-ohm impedance of the cable. This will cause serious signal distortion. For this reason, the ends of all the trunk and distribution cables are terminated with a 75-ohm load to ground.

Cable TV
A communications system which distributes broadcast programs and original programs and services by means of coaxial cable.

Cablecasting
To originate programming over a cable system. Includes public access programming.

Call Agent
In a PacketCable™ 1.0-based network, Call Agent is a synonym for Call Management Server (CMS). The term originates from the Simple Gateway Control Protocol (SGCP) specification. The Call Agent or CMS maintains network intelligence and call state, and controls the media gateway. “Server” is sometimes also used as a synonym for Call Agent or Call Management Server.

Call Appearance
A Call Appearance is an iteration of a telephone Directory Number (DN) that allows multiple concurrent calls to the same phone number. An ISDN line with three call appearances for a single DN, for example, can have three people on the line or on hold to the same number at the same time.

Call Detail Record (CDR)
A data record typically used in a telephony system to record usage information on a per-call basis. Typical fields in the record include originating number, terminating number, start-time, duration, etc.

Call Management Server (CMS)
In a PacketCable™ 1.0-based system, this is the entity that maintains call state and implements features, such as Custom Local Area Signaling Service (CLASS) features. The CMS controls both the in-home media gateways and the media gateways connecting to the Public Switched Telephone Network (PSTN). The CMS also performs admission control and routing functions.

Caller ID
Caller ID is a telephone company feature that notifies a telephone being called of who is (or at least what phone number is) originating the call. On analog POTS phone systems, Caller ID information is transmitted to the telephone set between the first and second ring of the phone. On ISDN sets, Caller ID data is sent as part of the Q9.31 “call setup” information sent of the ISDN D channel. Some states, like California, regulate the implementation of Caller ID very strictly, requiring that phone companies offer their customers the option of keeping their numbers private when placing a call.

Capability Package
ISDN Capability Packages, like Capability Package U, are standardized ISDN feature sets defined by ISDN Order Codes.

Carriage
A cable system’s procedure of carrying the signals of television stations on its various channels. FCC rules determine which signals cable systems must or may carry.
Carrier An alternating-current wave of constant frequency, phase and amplitude. By varying (modulating) the frequency, phase or amplitude of a carrier wave, information is transmitted.

Carrier Hum Modulation
The peak-to-peak magnitude of the amplitude distortion relative to the Radio Frequency (RF) carrier signal level due to the fundamental and low-order harmonics of the power-supply frequency.

Carrier-to-Noise Ratio (C/N or CNR)
The square of the ratio of the root mean square (RMS) of the voltage of the digitally-modulated Radio Frequency (RF) carrier to the RMS of the continuous random noise voltage in the defined measurement bandwidth. (If not specified explicitly, the measurement bandwidth is the symbol rate of the digital modulation; for video it is 4 MHz.)

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
The Ethernet media access method. All network devices contend equally for access to transmit. If a device detects another device’s signal while it is transmitting, it aborts transmission and retries after a brief pause.

Cartridge
Container for recorded programming designed to be shown on a television receiver. The cartridge contains a reel of motion picture film, videotape or electronically embossed vinyl tape, blank or recorded, and uses an external take-up reel.

Cascade Depth
The number of amplifiers between the headend and the specific subscriber.
Cascading Style Sheets (CSS) An extension to HTML to allow styles, e.g. colour, font, size to be specified for certain elements of a hypertext document. Style information can be included in-line in the HTML file or in a separate CSS file (which can then be easily shared by multiple HTML files).

Cassette
A self-contained package of reel-to-reel blank or recorded film, videotape or electronically embossed vinyl tape which is continuous and self-rewinding. Similar to a cartridge, but of slightly different design.

Cause Code
A numerical value that indicates the current status of an ISDN call session and what caused that change in status. See the ISDN Trouble Shooting: Cause Codes Web page.

C-band Satellite
3.7-4.2 gigahertz (Ghz) frequency band used for distribution of programming by most satellite and cable networks.

CCI
See Copy Control Information

CCCM
See CPE Controlled Cable Modem

Cell
ATM layer protocol data unit.

Cellular
A wireless telephone system where each geographic area (cell) is covered by a base station; users are handed over to other base stations as they move from cell to cell; analog and digital systems exist.

Central Office (CO)
A switching system that connects lines to lines and lines to trunks. The term is sometimes used loosely to refer to a telephone company building in which a switching system is located and to include other equipment (such as transmission system terminals) that may be located in such a building.

Certificate
A message that, at least, states a name or identifies the Certification Authority (CA), identifies the Subscriber, contains the Subscriber’s public key, identifies the Certificate’s Validity Period, contains a Certificate serial number, and is digitally signed by the CA that issued the certificate.

Certification Authority (CA)
An entity authorized to issue, manage, revoke, and renew Certificates.

Certificate of Compliance
The approval of the FCC that must be obtained before a cable system can carry television broadcast signals.

Certificate Revocation List (CRL)
A list of revoked certificates published by each certificate authority.

Channel
A transmission path between two points. The term channel may refer to a one-way path or, when paths in the two directions of transmission are always associated, to a two-way path. It is usually the smallest subdivision of a transmission system by means of which a single type of communication service is provided, i.e. a voice channel, teletypewriter channel, or data channel.

Channel Capacity
The number of channels available for current or future use on a cable system.

Chrominance Signal
That portion of the NTSC color television signal that contains the color information.

Cipher
An algorithm that transforms data between plaintext and ciphertext.

Ciphersuite
A set which must contain both an encryption algorithm and a message authentication algorithm (e.g., a MAC or an HMAC). In general, it may also contain a key-management algorithm, which does not apply in the context of PacketCable.

Ciphertext
The (encrypted) message output from a cryptographic algorithm that is in a format that is unintelligible.

Circuit Switched Data (CSD)
A type of telephone connection intended to carry data between two digital devices, such as ISDN digital data adapters and video conferencing systems. ISDN lines have to be provisioned correctly if they need to carry CSD connections.

Circuit-switched Network
This network transports information on communication links with a dedicated, end-to-end connection established at one or more switching centers between two connected parties for the length of their call. The public switched telephone network (PSTN) uses circuit switching.

Circuit Switched Voice (CSV)
A type of telephone connection intended to carry information between two analog-type devices, such as telephones, modems, and fax machines. ISDN lines have to be provisioned correctly if they need to carry CSV connections.

Classifier
A set of criteria used for packet matching according to TCP, UDP, IP, LLC, and/or 802.1P/Q packet fields. A classifier maps each packet to a Service Flow. A Downstream Classifier is used by the CMTS to assign packets to downstream service flows. An Upstream Classifier is used by the CM to assign packets to upstream service flows.

Cleartext
The original (unencrypted) state of a message or data. Also called plaintext.
Client Commonly used term in PacketCable parlance to signify the customer premises equipment.

Clipping
The shearing off of the peaks of a signal. For a picture signal, this may affect either the positive (white) or negative (black) peaks. For a composite video signal, the sync signal may be affected.

Closed Circuit
A system of transmitting TV signals in which the receiving and originating equipment are directly linked by cable, microwave or telephone lines, without broadcasting through the air.

Cluster
The group of homes passed by a single fiber node.

Clustering
Grouping together of independent cable systems into a larger, more efficient single system that utilizes some of the same infrastructure.

Coaxial Cable
Copper or copper-sheathed aluminum wire surrounded by an insulating layer of polyethylene foam, used by cable television systems. The insulating layer is covered with tubular shielding composed of tiny strands of braided copper wire, or a seamless aluminum sheath, and protective outer skin. The wire and the shielding react with each other to set up an electromagnetic field between them. This system reduces frequency loss and gives cable its great signal-carrying capacity.

Co-Channel Interference
One of the primary forms of man-made signal degradation associated with radio, co-channel interference occurs when the same carrier frequency reaches the same receiver from two separate transmitters as a result of spilling over from an adjoining cell.

Code Division Multiple Access (CDMA)
A spread spectrum access technology that assigns a code to each multiple access stream of data bits, transmits the spread data streams, and then, at the receiver, despreads and reassembles the data streams to their original format.

Coder-DECoder (CODEC)
A function or device that performs compression and decompression, typically on voice or video streams.

Codes Exchange (CODEX)
A telecommunications Codex specifies how different binary values sent across the telephone network are translated to a from specific sample voltages. See Codec.

Collision
The result of two network nodes transmitting on the same channel at the same time. The transmitted data is not usable.

Color Burst
In NTSC color, normally refers to a burst of approximately 9 cycles of 3.6MHz subcarrier on the back porch of the composite video signal. This serves as a color-synchronizing signal to establish a frequency and phase reference for the chrominance signal.

Color Subcarrier
In NTSC color, the carrier whose modulation sidebands are added to the monochrome signal to convey color information, i.e., 3.6 MHz (3.579545 MHz)

Combiner
A signal combining network that allows several discrete inputs to be added into a common bandwidth and that has high isolation between inputs. Also may refer to a power combining network.

Combining Network
A passive network that permits the addition of several signals into one combined output with a high degree of isolation between individual inputs. It may be a power or frequency combiner.

Common Carrier
Any point-to-point communications relay service available to the general public at non-discriminatory rates. The carrier cannot control message content (e.g., telephone companies).

Common Path Distortion (CPD)
The interference of return path signaling caused by the forward path.

Communication Satellite
An electronic retransmission vehicle located in space in a fixed earth orbit. Signals are transmitted to the satellite from earth station antenna, amplified and sent back to earth for reception by other earth station antennas.

Communication Server
A dedicated, standalone system that manages communications activities for other computers.

Competitive Local Exchange Carrier (CLEC)
An alternative local telephone company that competes against incumbent local exchange carriers (LECs) for local and access business. Also known as a competitive access provider (CAP) or alternate local telephone company (ALT). Companies that build high-bandwidth fiber-optic networks to compete with the incumbent telephone and cable operators. See also overbuilder.

Composite Second Order Beat (CSO)
The peak of the average level of distortion products due to second-order non-linearies in cable system equipment.

Composite Triple Beat (CTB)
The peak of the average level of distortion components due to third-order non-linearies in cable system equipment.

Composite Video Signal
The complete video signal. For monochrome, it consists of the picture signal and the blanking and synchronizing signals. For color, additional color synchronizing signals and color picture information are added.

Compression
A method for compacting the digital representation of a signal for more efficient transmission or storage.

Compulsory License
Legislation requiring copyright holders to license users of copyrighted material (cable television operators) on a uniform basis and for a stipulated fee.

Conditional Access (CA) and Encryption
Conditional access and encryption is a system that provides selective access to programming to individual customers in exchange for payment.

Confidentiality
A way to ensure that information is not disclosed to anyone other then the intended parties. Information is encrypted to provide confidentiality. Also known as privacy.

Connectionless Network
This is a type of packet-switched network in which no logical connection is required between sending and receiving stations. Each data unit or packet includes the source and destination addresses and can take any available route between source and destination. The Internet Protocol (IP) is connectionless.

Constant bit rate (CBR)
A service class intended for real-time applications, or those requiring tightly constrained delay and delay variation, as would be appropriate for voice and video applications. The constant availability of a fixed quantity of bandwidth is considered appropriate for CBR service.

Content
Content is typically used to refer to audio, video and graphic materials used by an application. Sometimes data and applications are also grouped into this term.

Content Protection/Copy protection (CP)
Content protection is a mechanism to protect the unauthorized copying of video and audio programming.

Contrast
The range of light and dark values in a picture, or the ratio between the maximum and minimum brightness values. A high-contrast picture would contain intense blacks and whites; a lower-contrast picture would contain only shades of gray.

Converter
Device that is attached between the television set and the cable system that can increase the number of channels available on the TV, enabling it to accommodate the multiplicity of channels offered by cable TV.

Cookies
A special text file that a Web site stores on your hard drive used to identify you to the Web site the next time you visit. A cookie records your preferences when using a particular site, and can also save the information filled out in online forms. They are used to send browser specific pages, or pages based on information you have provided to the Web site.

Coordinated Universal Time (UTC)
A reference time standard established by the CCIR (a predecessor of the ITU) and maintained by the Bureau International des Poids et Mesures (BIPM). Formerly Greenwich Mean Time (GMT).

Copy Control Information (CCI)
This information is stored on a CableCARD device and delivered to the host to control the copying of content. It is delivered to the CableCARD from the headend, based on arrangements made between the network operator and the content provider.

CPE Controlled Cable Modem
A cable modem in which a portion of the higher-layer processing is performed by an external device, in particular, by a PC.

Critical Length
Distance along a specific cable to cause worst-case mismatch reflection. A function of frequency-attenuation-velocity of propagation parameters of specific cable types.

Cross-Modulation
A form of television signal distortion where modulation from one or more television channels is imposed on another channel or channels.

Cross-Ownership
Ownership of two or more kinds of communications outlets by the same individual or business. The FCC prohibits television stations and telephone companies from owning cable systems in their service areas. Television networks are prohibited from owning cable systems anywhere in the U.S.

Crosstalk
Noise passed between communications cables or device elements.
Cryptanalysis The process of recovering the plaintext of a message or the encryption key without access to the key.

Cryptographic algorithm
An algorithm used to transfer text between plaintext and ciphertext.

CSR
Customer service representative.

CSV/CSD
An ISDN provisioning option that allows for both CSV and CSD telephone connections. Unless used to service an ISDN telephone, most home and business ISDN lines are configured to allow both.

Custom Local Area Signaling Services (CLASS)
This term refers to a set of voice telephony services that make use of information about the calling or called numbers. Examples are caller ID, Automatic recall (*69), anonymous call rejection, etc.

Customer Premises Equipment (CPE)
Equipment at the end user’s premises; MAY be provided by the end user or the service provider.

Cutoff Frequency
That frequency beyond which no appreciable energy is transmitted. It may refer to either an upper or lower limit of a frequency band.

Cyclic Redundancy Check (CRC)
An algorithm to detect data corruption.