TelevisionTutor- Glossary

Television Glossary & Links

Bullet Glossary

Listed below are terms used in the broadband, broadcast, and consumer side of the television experience. The mission of this glossary is to be concise. Therefore, all definitions are in one sentence consisting of thirty words or less. This format is meant to satisfy those readers looking for a "quick hit" for their understanding. Of course, in recognition that many technical concepts cannot begin to be described with this format, a link is provided to a search form for additional research. The user can highlight and copy the term or keywords in the definition, click the hyperlinked term, and paste the words into the form to allow a search.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Active

A powered electronic device that alters in some way the signal presented to it.

Aerial

In cable broadband, it is a reference to plant facilities hung on poles.

AFC

Automatic Frequency Control

Agile

A device capable of user frequency selection as opposed to being fixed in frequency.

AGC

Automatic Gain Control

Amplitude Modulation

AML

Amplitude Modulated Link

Amplifier

A device used to increase the strength of the signal supplied to it.

Analog

A descriptor for quantities varying continuously rather than in discrete steps.

Anchor

In aerial construction, a buried metal structure to which guy wires are tied.

Antenna

A device designed to collect or emit electromagnetic energy.

APL

Average Picture Level

Array

An arrangement of antenna elements or antennas for increasing the strength of desired signals while reducing the strength of undesired signals.

ATSC

Advanced Television Systems Committee

ASC

Automatic Slope Control

Aspect Ratio

Picture width to height (4:3 for NTSC and 16:9 for ATSC)

Attenuation

The loss of signal through transmission often expressed in decibels.

Attenuator

A device that is used to weaken the strength of the signal supplied to it.

Audio

A reference to electronically reproduced sound or the equipment processing it.

Aural Carrier

In analog television, the portion of channel radio energy carrying the sound.

Back Porch

A reference to that part of the video signal immediately following the horizontal sync pulse.

Bandpass Filter

A device that passes a range of frequencies while blocking frequencies outside that range.

Bandwidth

The useable range of frequencies of a given device or system.

Baseband

The originating signal information before it is modulated onto a radio frequency carrier.

Beamwidth

The angular width at which an antenna's receive or transmit capability drops to half power.

Beats

Undesired sum and difference frequency products created in an electronic device from two or more signals which can interfere with the desired signal.

Blacker-than-Black

Below reference black level (sync pulse direction) in a composite video signal.

Black Level

The brightness of black (peak) in a video signal (referenced in NTSC as 7.5 IRE).

Blanking

That part of the video signal where the amplitude and timing renders retrace as invisible.

Block Converter

A device that shifts a group of frequencies to a higher or lower grouping.

Block Tilt

Tilt in broadband plant achieved by stepped signal levels of groups of frequencies.

Breezeway

That part of the video signal between the sync pulse and the color burst.

Bridger

In cable broadband, it is the amplifier that is fed from the trunk and, in turn, feeds the distribution plant.

Broadband

In general, a large frequency capacity electronic device; in particular, a closed large capacity interactive electronic distribution system of multiple services to subscribers.

Broadcast

An open, limited frequency capacity electronic transmission serving the public.

C-Band

A satellite delivery system using a 3.7 - 4.2 GHz downlink.

Cable Modem

A device used at the subscriber household to receive and transfer data at high speeds.

CARS

Community Antenna Relay Service and Community Antenna Relay Station.

CATV

Community Antenna Television

Carrier or Carrier Wave

An electromagnetic wave that is dynamically altered in order to convey intelligence.

Cascade

Two or more amplifiers used in series to perpetuate an electronic signal.

CLI

Cumulative Leakage Index

Coaxial Cable

A broadband cable with a center conductor, insulating dielectric, and an outer shield.

Color Burst

In NTSC, a few cycles of the 3.58MHz color subcarrier imposed on the composite video signal back porch as a reference.

Co-Channel Interference

Interference created on a channel by a distant channel on the same frequency.

Combiner

A isolating passive device used to combine differing channel outputs into a single output.

Composite Video Signal

The complete video signal including blanking, synchronization, and color information (if used).

Converter

A frequency changing device of which the most commonly known version is the customer set-top box.

Core Shrink-back

When the center conductor of a coaxial cable or the entire cable itself pulls out of a connector due to temperature related contraction, also known a "suckout".

Cross Modulation

A type of distortion where modulation from a channel or channels is superimposed onto another channel when they pass through a non-linear circuit.

CRT

Cathode Ray Tube

Cycle

A complete change in a waveform from zero to a negative peak to zero, then to a positive peak and back to zero.

Decibel, a unit relating the ratio of two signal levels using a logarithmic scale.

dBm

Decibel Milliwatt.

dBmV

Decibel Millivolt.

DBS

Direct Broadcast Satellite.

dBW

Decibel Watt.

Demodulator

An electronic device used to remove the intelligence riding a carrier wave so that it may be displayed or processed.

Diplexer

In broadband, a device that combines or splits differing frequency carriers.

Dipole

A one-half wavelength center fed antenna consisting of two radiating elements.

Direct Pickup

Undesired broadcast station ingress from the air and into the cable television system or customer equipment

Directional Coupler

A passive device used to divide signals with the "through" port experiencing minimum loss, the "tap" port having a greater specified loss, and a high isolation loss between these ports.

Dish

A reference to a parabolic antenna commonly designed for use at microwave frequencies.

Distortion

Undesired changes in a signal waveform caused by the inherent nonlinearities of active devices and other processing elements of the transmission system.

Distant Signal

A television broadcast signal that is received outside of its Grade B contour.

DLP

Digital Light Processing

DOCSIS

Data Over Cable Service Interface Specification

Downlink

The signal transmission from a satellite to an earth station.

Downstream

The signal flow direction when it travels from the headend to the service subscriber in a cable broadband system.

Drop

The cable line connecting the subscriber household to the distribution plant of their broadband services supplier.

Earth Station

The antenna and associated electronic equipment needed for satellite communications.

Effective Height

The height of a antenna from ground in terms of its center of radiation rather than its physical location.

ERP

Effective Radiated Power

Egress

In cable broadband, it is the undesired leakage of signals from the plant into the air.

EIA

Electronics Industries Association

Electrical Length

In regard to performance, it is the effective length of an electrical device such as an antenna or transmission line (often expressed in wavelengths) rather than the physical length.

Electromagnetic Spectrum

The entire range of frequencies at which energy may be electromagnetically radiated which includes everything from subaudible frequencies to gamma ray frequencies.

Encoder

A device used to alter a signal so that it cannot be readily used unless another device (decoder) is authorized to do so.

Encryption

The act of applying algorithms or coding to information so that it cannot be used without the proper "keys" to do so.

Equalization

The application of frequency response devices to an electronic system to compensate for the frequency related losses of that system.

Equalizer

In cable broadband, a passive device designed with a frequency response tilt opposite of the inherent response tilt in the cable that precedes it.

FDM

Frequency Division Multiplexing

Feeder Cables

In a cable broadband system, it is the intermediate lines of distribution that carry the signals from the main trunk lines to the subscriber lines.

Field

One-half of a complete frame of video with each half being composed of either odd or even scan lines.

Field Strength

Also known as Field Intensity, it is the strength of a radio wave at a given point.

Filter

A passive device used to shape, pass,or block the frequency response of the signal fed to it.

Flooding Compound

A viscous material placed within a cable to guard against water infiltration.

Frequency Modulation

Footcandle

A measurement unit of illumination where 1 lumen is equally distributed across 1 square foot.

Footprint

The area of earth covered by a satellites directed beam.

Forward Direction

In cable broadband, the direction of signal flow from the headend to the subscriber.

Frame

A single complete video picture composed of the odd scan line field and the even scan line field interlaced together.

Franchise

Legal authorization issued by the local governing body (usually city, but can be county or state) to build and operate a cable television system in that jurisdiction.

Frequency

The cycles-per-second count of a given audio or radio wave

Frequency Response

The signal amplitude gain/loss across the frequency bandwidth of a given device or transmission system.

Frequency Suckout

A sharp signal loss or notch within a device or system's passband.

FSK

Frequency Shift Keying

Front Porch

The part of the video synchronization signal that follows the picture information and precedes the horizontal sync pulse.

Funny Paper Effect

The misregistration seen on video when the chrominance information either leads or lags the luminance information.

Gain

Usually expressed in decibels, it is the increase in signal strength through an amplifying device when comparing the output value to the input value.

Geostationary

A satellite that is in an orbit that allows travel that is synchronized with the earth's rotation, thus creating a constant "stationary" relationship.

Geosyncronous

See "Geostationary".

Group Delay

The difference in transmission time between frequency elements passing through an electronic device or medium.

Guard Band

Radio frequency spectrum left unused between channels in order to avoid interference.

Harmonic Distortion

Unwanted frequency multiples of the frequency fundamental(s) that are generated due to the nonlinearities of an electronic device.

HDMI

High Definition Multimedia Interface

HDTV

High Definition Television

Headend

The central electronics facility of a cable broadband system where all signal sources are generated, gathered, processed, combined, and fed into the trunking/distribution system.

Heterodyne

To electronically mix two frequencies together in a nonlinear device in order to produce two new frequencies equal to the sum and difference of the originating frequencies.

High Band

The band of frequencies covering 174MHz to 216MHz where channels 7 to 13 reside.

High Pass Filter

A filter that attenuates all frequencies below a designated cutoff point and passes all frequencies above that point

Home Theater

A recreation of the cinema experience in the home that can range from simple multichannel sound and large screen enhancements to the construction of theater staging and seating.

HRC

Harmonically Related Carriers

Hub

A signal processing facility located between the headend and the signal distribution system in order to provide customized regional services.

Hue

The dominant optical wavelength that causes visual perception to distinguish a particular color apart from others.

Hum

In audio, it is a low pitched interference tone often picked up from AC power sources, while in cable broadband it is often a reference to visual Hum Modulation.

Hum Modulation

The undesired modulation of the visual carrier by power line frequencies and harmonics (or other low frequency disturbances) sometimes visible as bars rolling through the picture.

Hertz, a measure of frequency known formerly as "cps" or "cycles-per-second" but renamed in honor of Heinrich Rudolph Hertz who furthered the understanding of electromagnetic waves.

Intermediate Frequency

Impedance

The total resistive and reactive opposition to the flow of an alternating current signal at a given frequency.

Impulse Noise

Short duration transient disturbances.

Inductor

A coiled conductor designed to oppose changes in current by virtue of its concentrated magnetic field.

Infrared

The section of electromagnetic spectrum just below visible light.

Ingress

The undesired influx of interference into a cable broadband system from sources outside of the system.

IRC

Incrementally Related Carriers

Isolation

The attribute of a device that minimizes signal transfer from one point to an inappropriate point.

Jitter

An unstable picture usually caused by disturbances to synchronization.

Jumper Cable

In cable broadband, it is a short length of coaxial cable used to connect close proximity devices such as a converter box and the customer television.

Ku Band

The band of microwave frequencies extending from 12 to 18GHz (in North America, the reference commonly refers to the 11.7 to 12.2GHZ satellite downlink portion).

LASER

Light Amplification by Stimulated Emission of Radiation

Lasher

A machine used in aerial construction to tie the communications lines to the support strand by spin-wrapping wire around the cable bundle.

LCD

Liquid Crystal Display

LCoS

Liquid Crystal on Silicon

Leakage

Undesired signal emissions from a cable broadband system (often from cable cracks or poor connections) into the air.

LED

Light Emitting Diode

Line Extender

An amplifier used in the distribution system of cable broadband to extend the reach of the signal.

Line-of-Sight

An unobstructed path through open space intended for transmit/receive stations such as point-to-point microwave, satellite-to-earth transmissions, and optical laser links.

LNA

Low Noise Amplifier

LNB

Low Noise Block Converter

LNC

Low Noise Converter

Local Origination

Programming produced and telecast from the local cable broadband provider.

Local Oscillator

The oscillator in superheterodyned equipment that generates the proper frequency signal needed to mix with the received signal to produce the desired intermediate frequency.

Local Signals

Television broadcast signals received within their respective Grade B contours.

Log Periodic Antenna

A directional antenna with the radiating elements and spacing arranged in logarithmically increasing dimensions in order to provide wideband reception or transmission.

Low Band

The band of frequencies covering 54MHz to 88MHz where channels 2 to 6 reside.

Low Pass Filter

A filter that attenuates all frequencies above a designated cutoff point and passes all frequencies below that point

Lumen

The unit of light flux from a point source of one candle through a unit solid angle.

Luminance Signal

The part of the television signal that carries the brightness information and can produce a complete monochromatic picture.

Makeready

The process in cable broadband where the readiness of underground and poleline facilities are ensured prior to construction.

MATV

Master Antenna Television System

MDS

Multipoint Distribution System

MCR

Master Control Room

Messenger

Refers to either the supporting steel strand to which hardline coaxial cable may be lashed or the supporting steel wire embedded in the jacket of aerial coaxial drop cable.

Microwave

A reference to those radio waves with a frequency above 1000MHz.

Mid Band

The band of frequencies covering 120MHz to 174MHz where cable channels A to I reside.

Midspan

A point on the strand and coaxial distribution cables located between two utility poles.

MMDS

Multichannel Multipoint Distribution Service

Modulate

To alter a constant carrier wave's amplitude, frequency or phase by impressing a varying intelligence wave onto it.

Modulation

The electronic process used to impress intelligence onto a carrier wave for transportation to a distant recovery location.

Monitor

A term usually applied to a television, a speaker, or other studio equipment used in observing the quality of signal and can also apply to the act of observance itself.

MTS

Multichannel Television Sound

NAB

National Association of Broadcasters

NCTA

National Cable Television Association

Noise

Random electron movement in an electronic curcuit that influences the desired signal passing in that circuit.

Noise Figure

The expected amount of noise in decibels added by a given electronic signal processing curcuit.

Noise Temperature

A noise contribution rating derived by positing the temperature of a resistor connected to an ideal amplifier compared to the actual amplifier were it connected to a resistor at 0K.

Notch Filter

A filter designed to pass all frequencies except for that at which it is tuned to attenuate.

NTC-7

Network Transmission Committee guidelines for the placement of test signals in the vertical interval of an NTSC television signal for testing transmission performance.

NTSC