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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T-1
A type of high-speed digital data connection that operates at 1.54Mbps and requires a two-pair (four-wire) connection between the telephone company Central Office and the customer premises. See also Fractional T-1.

T-carrier system
A digital transmission system that takes analog voice circuits and converts them to digital form for transmission using time division multiplexing. The T-0carrier system was designed to operate at different rates, known as T1 (1.544 Mbps, equivalent to 24 channels); T2 (6.312 Mbps, equivalent to 96 channels); T3 (44.736 Mbps, equivalent to 672 channels); and T4 (274.176 Mbps, equivalent to 4,032 channels). (Without compression, a 64-Kpbs channel carries a single voice conversation.) Carrier systems are not always channelized; the entire system can be used to carry high-bandwidth communications.

Take Rate
The ratio of homes that pay for a cable service to homes passed.

Tap
A tap is a device which splits off a portion of the feeder line signal for the subscriber.

Tariff
A set rate and service schedule established by agreement between the phone company and a government-run regulatory agency, called the Public Utilities Commission.

T-Commerce
Television commerce, an interactive television application which enables electronic transactions between businesses and consumers via television.

Tearing
A term used to describe a picture condition in which groups of horizontal lines are displaced in an irregular manner. Caused by lack of horizontal synchronization.

Telco
A local exchange telephone carrier.

Telecommunications
Communicating over a distance through wire, radio, optical or other electromagnetic means.

Telecommunications & Internet Protocol Harmonization Over Network (TIPHON)
A project within the European Telecommunications Standards Institute (ETSI) aimed at enabling systems level interoperability for Voice Over IP technologies. ETSI has historically been focused primarily on H.323-based systems; however, they recently have become interested in MGCP-based technologies, such as PacketCable NCS.

Telecommunications Management Network (TMN)
A management concept that defines the relationship between basic network functional building blocks (operations systems, data communications networks, and network elements) in terms of standard interfaces. For more information refer to www.nmf.org and for protocol specifics and additional information refer to the International Telecommunications Union (ITU) at www.itu.ch.

Teledensity
Teledensity refers to the number of telephone lines (including wired residential and business lines) per 100 people, a rough measure of the ubiquity of the public switched telephone network (PSTN) in a country.

Telephone Number (TN)
A 10-digit number that specifies the location of a particular telephone and consists of a 3-digit area code, 3-digit central office code, and 4-digit station number.

Teletext
Broadcast service using several otherwise unused scanning lines (vertical blanking intervals) between frames of TV pictures to transmit information from a central database to receiving television sets.

Television
The electronic transmission and presentation of pictures and sounds.

Television Households
A household having one or more television sets. Estimates for each county are based on an updating of ARB (American Research Bureau) TV penetration estimates. The number of households that watch television in any locality during prime-time hours determines the top 100 markets for FCC cable rules.

Television Market
A city or complex of closely associated cities served by commercial television broadcast signals from one or more TV stations located within the area. The FCC uses television markets for designating what kind of cable services an operator should provide in terms of signal carriage and nonbroadcast channel use.

Television Receiver-Only (TVRO)
The receiving antenna dish, or complete package or dish receiver.

Telnet
A TCP/IP protocol which allows terminal-type login access to computers on the Internet for the purpose of entering remote commands. The protocol name is capitalized; when used in the form “telnet,” it refers to the client software that implements the protocol, or the act of using the protocol.

Terminal
Generally, connection point of equipment, power or signal. Any “terminating” piece of equipment such as computer terminal.

Terminal Endpoint Identifier (TEI)
An unique number that the telephone company switching equipment assigns to each ISDN adapter when it is turned on or connected to a telephone line.

Terminator
A resistive load for an open coaxial line to eliminate reflections; usually capacitively coupled to avoid shorts in cable-powered systems.

Test Execution Package (TEP)
The actual set of instructions, scripts, results tables, and any other document used to test and report compliance with certain specifications.

Thickwire
Half-inch diameter coax cable.

Thinwire
Thin coaxial cable similar to that used for television/video hookups.

Third Harmonic
A third order beat whose three beating carriers all have the same frequency.

Third Order Beat
An unwanted carrier created by three separate carriers beating against each other. These beating carriers may have the same or different frequencies.

Threshold
The minimum level at which a signal of any kind can be detected, either by the human senses or by using any electronic instrument.

Throughput
The speed at which the data is received. Throughput can be increased by compressing data before it is transmitted, then decompressed when it is received, or by using a more efficient transmission protocol.

Tick
The 6.25-microsecond time intervals that are the reference for upstream mini-slot definition and upstream transmission times in the DOCSIS protocol.

Ticket Granting Server (TGS)
A sub-system of the KDC used to grant Kerberos tickets.

Tiered Programming
A group of programs for which the customer is charged a fee. For example, most cable systems offer a satellite programming tier.

Tiering
Supplying cable subscribers with one or more program services beyond the basic offerings at an extra charge. Each additional price increment is called a tier.

Tilt
Maximum difference in transmission gain of a cable television system over a given bandwidth (typically the entire forward operating frequency range).

Time Division Duplex (TDD)
The method of multiplexing transmit/ receive (uplink/downlink) parts of a wireless communications link together; the exchange of uplink and downlink information takes place on the same frequency, but is distinguished by time-slot characteristics (see also frequency division duplex).

Time Division Multiplexing Access (TDMA)
A multiple access physical layer technology that enables a large number of users to access, in sequence, a single channel without interference by allocating unique time slots to each user within each channel. DOCSIS 1.0, 1.1, and 2.0 use TDMA technology.

Time of Day (ToD)
An internet protocol used by a device to learn the current time from a ToD server.

Token
The character sequence or frame, passed in sequence from node to node, to indicate that the node controlling it has the right to transmit for a given amount of time.

Token Ring
Developed by IBM, this 4 or 16 Mbps network uses a ring topology and a token-passing access method.

Top 100 Market
Ranking of largest television broadcast areas by size of market; i.e., number of viewers and TV households. Used in FCC rulemaking and in selling of airtime to advertisers.

Topology
The arrangement of the nodes and connecting hardware that comprises the network. Types include ring, bus, star and tree.

Total Activity Report (TAR)
A quarterly Nielsen report which lists all the television activity during a sweep including broadcast stations, basic cable, pay cable, and superstations. It shows household rating and share delivery by daypart in both the DMA (total market) and cable household universe for all program sources.

Traceroute
A command-prompt utility in MS-DOS and UNIX that reports the gateways, or hops, that your data travels through on the Internet to reach its destination.

Traffic Parameter
A parameter for specifying a particular traffic aspect of a connection.

Transaction Capabilities Application Part (TCAP)
TCAP is a protocol within the signaling system number 7 (SS7) suite of protocols that is used to perform database queries across the SS7 network.

Transaction Language 1 (TL/1 or TL-1)
A management interface protocol defined to configure and manage Telco systems. Telco operations systems support (OSS) providers define this language. The TL-1 provides a specific syntax and it varies from one network element to another vendor.

Transceiver
A combination of a transmitter and a receiver having a common frequency control and usually enclosed in a single package. Extensively used in two-way radio communications at all frequencies.

Transducer
A device that converts one form of energy or disturbance into another. Transducers convert AC and DC into sound, radio waves, or other forms.

Transient application
A transient application is an application that must be downloaded before it can be run and may be deleted afterward. Transient applications, such as a program enhancement, are typically delivered via the broadcast system or by request if 2-way functionality is present.

Transimpedance
The transfer function of a TIA, the output voltage divided by the input current.

Transistor
A semiconductor device consisting of three or four layers used for switching or amplification at frequencies ranging from direct current to ultra-high.

Transit Delays
The time difference between the instant at which the first bit of a PDU crosses one designated boundary, and the instant at which the last bit of the same PDU crosses a second designated boundary.

Translator
Relay system that picks up distant television signals, converts the signals to another channel to avoid interference, and retransmits them into areas that the original television signal could not reach.

Transmission Amplifier (TIA)
A device used to convert input currents to output voltages.

Transmission Control Protocol (TCP)
A transport-layer Internet protocol which ensures successful end-to-end delivery of data packets without error.

Transmission Control Protocol/Internet Protocol (TCP/IP)
The most common protocol used for communication between computers on a network. Originally developed by the US Department of Defense for a worldwide communications network that eventually developed into the Internet.

Transmission Convergence Sublayer
A sublayer of the physical layer that provides an interface between the data link layer and the physical media dependent (PMD) Sublayer.

Transmission Link
The physical unit of a subnetwork that provides the transmission connection between adjacent nodes.

Transmission Medium
The material on which information signals may be carried; e.g., optical fiber, coaxial cable, and twisted-wire pairs.

Transmission System
The interface and transmission medium through which peer physical layer entities transfer bits.

Transmit Delay
The time difference between the instant at which the first bit of a PDU crosses one designated boundary, and the instant at which the last bit of the same PDU crosses a second designated boundary.

Transmit On/Off Ratio
In multiple-access systems, the ratio between the signal powers sent to line when transmitting and when not transmitting.

Transponder
The part of a satellite that receives and transmits a signal.

Transport Layer Security (TLS)
An Internet security protocol based on SSL.

Transport Stream
In MPEG-2, a packet-based method of multiplexing one or more digital video and audio streams having one or more independent time bases into a single stream.

Trigger
A trigger is an event that may cause a change in the behavior of a DVB-HTML application that registers interest in such events. Triggers may come from many sources (for example, the broadcast stream) or may be generated from other data (such as the system clock), or may be generated as a result of user interaction. The trigger may include a reference to time, which may be absolute (UTC), relative to some other event, relative to the NPT of a media stream. It also can carry some semantically significant payload in order to affect changes in an application based on information not available at the time an application was written.

Triple Beat
A third order beat whose three beating carriers all have different frequencies, but are spaced at equal frequency separations.

Trivial File-Transfer Protocol (TFTP)
An Internet protocol for transferring files without the requirement for user names and passwords that is typically used for automatic downloads of data and software.

Trunk
An analog or digital connection from a circuit switch which carries user media content and may carry telephony signaling (MF, R2, etc.). Digital trunks may be transported and may appear at the Media Gateway as channels within a framed bit stream. Trunks are typically provisioned in groups, each member of which provides equivalent routing and service.

Trunk Amplifiers
The amplifiers along the trunk line responsible for maintaining signal strength must have low distortion, low noise, and moderate gain. Degradation of the signal along the trunk cannot be corrected downstream, in fact, cascade amplifiers with similar faults simply amplify the fault too. Trunk amplifiers compensate for cable losses with automatic slope control (ASC) and automatic gain control (AGC).

Trunk Cable
Cables that carry the signal from the headend to groups of subscribers. The cables can be either coaxial or fiber depending on the design of the system.

Trunk Circuit
A circuit, part of a switching system, associated with the connection of a trunk to the switching system. It serves to convert between the signal formats used internally in the switching system and those used in the transmission circuit, and it performs logic and sometimes memory functions associated with supervisors.

Trunk Line
The major distribution cable used in cable television. It divides into feeder lines which are tapped for service to subscribers.

Trunking
Transporting signals from one point (an antenna site for instance) to another point (such as a headend), usually without serving customers directly. Trunking can be accomplished using coaxial cable, fiber optics or microwave radio.

Tunnel Mode
An IPsec (ESP or AH) mode that is applied to an IP tunnel, where an outer IP packet header (of an intermediate destination) is added on top of the original, inner IP header. In this case, the ESP or AH transform treats the inner IP header as if it were part of the packet payload. When the packet reaches the intermediate destination, the tunnel terminates and both the outer IP packet header and the IPsec ESP or AH transform are taken out.

TV Penetration
The percentage of homes having one or more television sets at the time of the ARB (American Research Bureau) survey. The ARB surveys local markets from October through July; the number of surveys in a year depends on the size of the market.

Twisted Pair
A pair of wires used in transmission circuits and twisted about one another to minimize coupling with other circuits. Paired cable is made up of a few to several thousand twisted pairs.

Two-way
Bidirectional communications over the same communication medium.

Two-way Capacity
A cable television system with two-way capacity can conduct signals to the headend as well as away from it. Two-way or bi-directional systems now carry data; they may eventually carry full audio and video television signals in either direction.

Two-way System
The ability to receive TV programming through the broadband network and send information back through the same network. This capability is used by customers to order movies and music and to interact in other manners with the Broadband network.

Type of Service (ToS or TOS)
A field within an IP packet that can be used to request priority treatment of the packet by the network. The ToS field and mechanism have been replaced by Differentiated Services (DiffServ) and DiffServ Codepoints (DSCPs).

Type/Length/Value (TLV)
An encoding of three fields, in which the first field indicates the type of element, the second the length of the element, and the third field the value.

Typical Operating Conditions
Optimum operating conditions for a stated number of channels.