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Audio / Video Terms Index


Select a letter below to view an index of terms and their definitions


ABCDEFGHIJKLM
NOPQRSTUVWXYZ

A

Activity Detection

A feature used in multiplexers that uses video motion detection techniques to improve the camera update times. It can also give a relay closure.

Alarming

The ability of CCTV equipment to respond to an input signal, normally a simple contact closure. The response varies depending on equipment type.

Alkaline Cell/Battery

Modern, high-performance, non-rechargeable cells and batteries used in most modern "battery-driven" electrical and electronic consumer devices.

All-laminated Core

A special permalloy laminated core production process is used to reduce eddy current loss and improve the linear response range of the cartridge's magnetic circuit.

AM (Amplitude Modulation)

Method of signal broadcast transmission used for radio.

AM Wide-Band Tuner

Picks up higher frequency range AM signals (from 1610kHz to 1710kHz) to receive newly allocated additional stations.

Ampere

The internationally accepted unit for the measurement of current flow (migrating electrons) in an electronic circuit. One ampere of current will flow through one ohm of resistance under the influence of one volt.

Angle Of View

The angular range that can be focused within the image size. Small focal lengths give a wide angle of view, and large focal lengths give a narrow field of view.

Anti-Skating Device

A carefully calibrated, adjustable device acting on the tone arm near its rotational center to counteract the natural tendency of the tone arm to move toward the center of the record, thereby holding the stylus centered in the record groove. Spring-mounted or suspended weight systems are typically used.

AP

Standard hole size for XLR-type and other audio connectors. Measures 7/8" diameter.

Aperture

The opening of a lens which controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment. By increasing the f stop number (f1.4, f1.8, f2.8, etc.) less light is permitted to pass to the pickup device.

Armature

The moving portion of a magnetic circuit. In a motor, the rotating center as opposed to the stationary stator. The coils in a MC cartridge; the magnet in a MM cartridge.

Aspect Ratio

The ratio of the picture frame width to the picture frame height in standard TV systems. It is 4 units horizontal over 3 units vertical.

Aspherical Lens

A lens designed with a non spherical shape so that it refracts the light passing through it to either lower the lens aperture so that it passes more light or decrease barrel distortion on wide angle lenses.

Attenuation

used to lower the strength of a signal to better suit an application. In the case where a speaker is playing too loudly, an attenuator can be used to turn it down. In the case where a video signal is saturated, an attenuator can lower the strength to level out the picture.

Automatic Frequency Control (AFC)

An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.

Automatic Gain Control (AGC)

A feature on Automatic lris lenses (also known as the peak/average control). Adjusting this control allows the automatic iris circuitry to either take bright spots more into consideration (peak), bringing out detail in bright areas, or less into consideration (average) bringing out detail in shadows.

Automatic Power-Off

Automatically turns off the unit when no signal has been received for an extended period of time.

Automatic Preset Station Memory

Automatically scans the band width and presets available signals in the area in which you are traveling.

Automatic Reverse

Reverses the direction of the tape to play the second side when the end of the first side is reached. Allows repeated cassette playback for continuous listening.

Automatic Stop

Helps protect tape and prolong battery life. When tape reaches the end during playback, the unit stops and power shuts off automatically.

Automatic Tape Selector

Reads the tape being used to determine its formulation (metal, Cr02 or normal), then sets proper bias and equalization automatically.

Automatic Terminating

A feature where the equipment (ex. Monitor) automatically selects the correct termination depending on whether the video output BNC is connected.

Automatic White Balance

A feature on color camera that constantly monitors the light and adjusts its color to maintain white areas. A/V (Audio/Video): Refers to equipment that uses or controls audio and video signals.

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B

Back Focal Distance

The distance from the rear most portion of the lens to the image plane.

Back Light Compensation (BLC)

A feature on newer CCD cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted.

Balance Weight

A weight to balance the tone arm and adjust the tracking force. Also called "counterbalance".

Battery

An electro-chemical device, consisting of separate cells connected together to sum their voltages or current capabilities. Examples: lead-acid, alkaline, 9-volt, gel cell and many others.

BL

A measurement of the motor strength of a speaker driver. Measured in Newtons per Ampere (N/A), Tesla meters Tm, pounds per Ampere (lbs/A) or Tesla feet (T/ft)

Blooming

The halation and defocusing effect that occurs around the bright areas of the picture (highlight) whenever there is an increase in the brightness intensity.

Black Level

The level of the video signal that corresponds to the maximum limits of the black areas of the picture.

Blanking

The process of cutting off the electron beam in a camera pickup device or picture tube during the retrace period. It is a signal that is composed of recurrent pulses at line and field frequencies. It is intended primarily to make the retrace on a pickup device or picture tube invisible.

Bridging

A term indicating that a high impedance video line is paralleled, usually through a switch, to a source of video. Also the use of two outputs of an audio amplifier to drive a single speaker load.

Brushless Motor

A motor eliminating sliding contact conductive material or carbon blocks and using instead an electronic switching circuit to change the polarity of the stator. There is no direct contact between rotor and stator.

Butt Connector

crimp connector used to attach two stripped ends of wire, end to end.

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C

C mount/CS mount

CCTV lenses are available in two different lens mounts. "C-mount" lenses have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. Many of today's cameras can accept either type of lens, but it is important to make sure that camera and lens are compatible and set up properly. C-mount lenses can be used on CS-mount cameras by utilizing a 5mm adapter or adjusting the camera for C-mount lenses. Because of the shorter back focal distance, CS-mount lenses can only be used on CS-mount cameras. Your picture will be out of focus if you use a CS-mount lens on a C-mount camera.

CATV (Community-Antenna Television)

Also called cable TV. Broadcasting method that uses a central antenna to feed off-air broadcast programming to an entire community through a hard-wired network.

Cardioid

Heart-shaped pick-up pattern of a microphone. (This means that the microphone can "hear" sounds coming from directly in front of and to the sides of the microphone head, but not behind it.) Useful in isolating sounds in loud environments and avoiding sound-system feedback.

Candlepower

The unit measure of an incident (direct) light.

Cantilever

The part of a cartridge that transmits vibrations, first picked up by the stylus tip from a record, to the electromagnetic generating unit.

Cartridge

A transducer that converts the mechanical vibrations caused by the record groove undulations into an electric signal.

Cat 5 (Category 5) or Cat 3 (Category 3)

refers to specific building regulations for structural and fire safety to which the materials (usually wire and cable) conform.

CCD (Charged Coupled Device)

A chip that is the pick up devise on a camera, performing a similar function as a camera tube.

CCTV

The common abbreviation for Closed Circuit Television. Video signals that are generated and viewed in the same area. Many times corporations use this type of system for training and other information within their facilities. Home security video monitoring systems can also be considered CCTV.

Cell

A single-unit, self-contained, voltage/current source. Has positive connectors for use with electrical or electronic devices, alone or along with other cells. Examples of cells: AA, AAA, C, D, button cells and many others.

Chrominance Subcarrier

Frequency used to establish a reference for demodulating the chrominance signal.

Cms

The mechanical compliance of a speaker driver's suspension (surround, cone and spider). Measured in inches per pound or millimeters per Newton.

Coatings

Light is lost by reflection from optical surfaces that are intended to be refractors only. This loss is effectively reduced by very thin coatings on the lens surfaces. This can be seen as a blue or violet hue on the lens surface.

Coaxial

Circles that share the same center-point (axis). Used to describe cable and speakers.

Coaxial cable

Consists of center signal-carrying conductors and outer shielding conductors that share the same center axis. The outer shield prevents interference of outside noise and signals from distorting or weakening the signal traveling across the center conductors.

Coaxial speakers

Consists of woofers and tweeters that are mounted together such that they share the same center axis. The theory here is that sounds coming from speakers that share the same centerpoint are supposed to sound as though they are coming from one source as opposed to separate drivers.

Comb Filter

Circuitry that electronically separates the color (chrominance) from the picture (luminance) signal, to enhance fine detail with minimal color spill or picture "noise" (distortion).

Combiner

Used to combine similar signals into one cable. Used for UHF/VHF and CATV signals.

Composite Video

The combined video signal that includes the picture signal, the vertical and horizontal blanking and synchronizing pulses. Examples of composite video sources: "Video Out" connection points, usually RCA jacks, on VCRs, DVDs, satellite receivers, home video cameras, surveillance cameras, "web-cam" cameras, etc.

Compression-type Connector

A connector that is attached to a wire or cable such that when the connector is assembled, it's parts grip into the wire to which they are attached.

Conditional Refresh

A technique used in slow and fast scan transmission equipment, where only small screen changes are transmitted. Up to a certain percentage of the on-screen picture can be updated before a full picture is required.

Crosstalk

An undesired signal that interferes with the desired signal.

Crossover

Splits an audio signal into different frequency ranges (low, middle and high) for use with different types of speaker drivers (woofers, midranges and tweeters) or to be routed to different amplifiers in a multi-amp system.

Current

The organized migration of electrons through a circuit or conductive material, as the result of an applied voltage and the presence of resistance.

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D

d

The speaker system damping factor of a 4th order bandpass cabinet.

D/A (Digital To Analog) Converter

Circuitry that converts a digital (binary) signal into an equivalent analog waveform. In an audio system, this is done so the signal from digital storage media, such as MiniDisc, CD, or Digital Audio Tape, can be handled by analog system components, such as the receiver and speakers. See 1-bit DM Converter.

DAT (Digital Audio Tape)

An audio tape format Sony helped develop that uses linear digital encoding to produce audio with the dynamic range and clarity of a CD on a cassette that is 30 percent smaller than a regular audiocassette.

dB (Decibel)

Unit of measure of signal strength. A measure of the power ratio of two signals. It is equal to ten times the logarithm of the ratio of the two signals. Higher dB means stronger signal.

DBS (Direct Broadcast Satellite)

Sometimes referred to as Direct Broadcast Service. A system that employs an uplink center to transmit signals to a satellite, which in turn feeds the signal directly to a satellite dish antenna at a subscriber's location. DSS is a type of DBS.

DC-type Lens

An automatic-iris lens with internal circuit which receives voltage and a video signal from the camera to adjust the iris.

Demodulator

converts and/or splits a modulated signal into its component parts (e.g. a VHF/UHF demodulator splits television signals into separate audio and video signals). An FM radio is a demodulator in that it receives a broadcast signal and demodulates the audio so it can be heard.

Depth Of Field

The front to back zone in a field of view which is in focus in the televised scene. With a greater depth of field, more of the scene, near to far, is in focus. Increasing the f-stop number increases the depth of field of the lens. Therefore, the lens aperture should be set at the highest f-stop number usable with the available lighting. The better the lighting, the greater the depth of field possible. In other words, the depth of field is the area in front of the camera which remains in focus. The larger the f-number the greater is the depth of field.

Dia

The "piston" diameter of a speaker driver.

Die Casting

Process where molten metal is poured into a mold. Designed to offer greater precision and vibration resistance than parts made of stamped sheet metal. Used for quality turntable platters and speaker frames.

Digital

A signal that levels are represented by binary numbers.

Digital Comb Filter

advanced circuitry that digitally separates the color (chrominance) signal from picture (luminance) signal, for even greater enhancement of fine detail and significantly reduced picture "noise" (distortion).

Digital Intelligent Comb Filter

An advanced comb filter circuitry converts the incoming signal to digital information, analyzes it, and automatically selects the correct comb filter process that will deliver the best picture and the highest resolution with a minimum of dot-crawl interference.

Digital Synthesis Tuner

A radio receiver system that uses digital calculations based on an ultra-precise quartz crystal reference signal, for crisp, clear drift-free station tuning.

DIP (Dual In-line Package)

A semiconductor design that consists of two rows of pins.

Direct-drive System

A turntable system using a low speed motor (that turns at 33.3 or 45 rpm) directly coupled to the platter so that the motor shaft is one with the spindle.

Dispersion

(Speakers) A radiation or diffraction of energy (sound waves) from the energy source. For speakers, dispersion is a measured distribution of sound within a listening area. A wide dispersion is better in most cases for even distribution of sound within the listening area (although there are instances where pinpointed, narrow dispersion is beneficial, like in office P.A. systems where there may be feedback).

Distribution Amplifier

A device that accepts a (video) signal and sends it out to a number of independent outputs that are of the same strength as the incoming signal.

DMM (Digital Multi-Meter)

A piece of electronics testing equipment that measures electrical qualities of a circuit or component. Most commonly measures resistance (ohms), current (amperes or amps) and voltage (volts).

Dolby HX Pro® Headroom Extension

Circuitry designed and licensed by Dolby Laboratories and used in many Sony tape decks. It can increase the highest sound level in an audio signal that a component can handle without generating distortion, so you can record at higher peak levels. Operating during the recording of a cassette, the Dolby HX professional system monitors the level of the input signals and optimizes the bias level accordingly. The result is a dramatic improvement in the dynamic range of high frequencies.

Dolby Noise Reduction(Dolby B, Dolby C, Dolby S)

Circuitry designed and licensed by Dolby Laboratories, used to suppress "noise" (extraneous sound or interference) during recording and playback of audiocassettes. Dolby B and Dolby C both amplify weaker sounds during the recording process, and return them to correct levels during playback to increase dynamic range. Dolby S is the most advanced form. Used in record and playback modes, it can enhance an audiocassette deck's dynamic range to near-CD quality.

Dolby Pro Logic® Surround Decoding

Circuitry available on many home audio receivers that can process the Dolby Surround encoding found on most movie soundtracks and some network TV shows. It involves the playback of 4-direction sound (left, right, center and rear) and steering logic (directional circuitry). When used in conjunction with such equipment as an AV Laser player, a VHS Hi-Fi Stereo VCR, and a surround sound speaker package, it offers the realism and dramatic impact of top quality movie theater sound.

Driver

An individual "speaker" in a loudspeaker system. Also a piece of software or programming that translates information traveling between two or more components in a computer system.

DSP (Digital Signal Processing)

The manipulation of an audio signal in the digital domain, to maintain clearer sound with less distortion and noise than with analog processors. Digital signal processors can perform equalizing and crossover functions; automatic sound DSP units can compensate for seating position to deliver optimized sound to each position in a vehicle. DSP units can also create the ambience of different listening environments, such as a concert hall or jazz club.

DSS (Digital Satellite System)

A standard format of digital satellite broadcast transmissions.

Dv

The inside diameter of the port tube in a vented cabinet speaker system.

Dwell Time

The length of time a switcher holds on a camera before moving on to the next in sequence.

Dynamic Range

The difference between the softest and loudest sounds contained on an audio source that an audio component can reproduce; measured in decibels (dB). A higher number indicates greater dynamic range.

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A

EBP

The efficiency bandwidth product of a speaker driver. Equals the Fs divided by the Qes.

EI (Electronic Iris)

Automatically changes a CCD camera¹s shutter to mimic Automatic Iris control, allowing fixed or manual iris lenses to be used in a range of areas that used to require an automatic iris lens.

EIA (Electronic Industry Association)

US reference standard for electronic components. Example: an EIA standard for TV is 525 lines, 60 fields per second.

8x (eight times) Oversampling Digital Filter

Prevents the deterioration of phase characteristics by converting the 44.1 kHz sampling frequency into 8 times the base frequency, cutting signals more gently for improved phase characteristics.

Electronic shuttering

Electronic shuttering is the ability of the camera to compensate for moderate light changes in indoor applications without the use of automatic iris lenses.

Elliptical Stylus

A stylus tip having an elliptical cross section, as opposed to a conical shaped stylus.

E-M

The electro-mechanical parameters of a speaker.

Equalization

The process of correcting losses of certain components in a signal.

Equalizer (EQ)

Used to adjust or "equalize" various bands of frequencies in an audio system. Bass and Treble are very basic equalizers of two (low and high) frequency-band levels. Equalizers with more frequency bands (7, 10, 15, etc.) simply do the same thing, but break down the frequencies you can hear into smaller groups or bands of frequencies whose levels can be independently controlled.

EP

Standard mounting hole size for Speakon and other audio connectors. Meaures 1-1/4" diameter.

ESP (Electronic Shock Protection)

On portable CD players with this feature, digital circuitry creates a buffer that holds several seconds of audio in memory. If the laser skips during playback, this memory buffer can allow audio to continue uninterrupted until the laser regains the correct position. On selected portable CD players, Super ESP circuitry increases the length of the buffer for even greater protection against skipping.

Extension tube

Kit consisting of various size spacers that are used between the lens and the camera to reduce the lens M.O.D. Generally used for very close-up applications. Not recommended for zoom lenses due to loss of tracking.

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F

Fb

The resonant tuning frequency of a vented speaker cabinet.

Fc

The resonant frequency of a sealed speaker cabinet.

F connector (short for "RF connector")

Coaxial connector used mainly for CATV, CCTV and satellite TV systems.

Feedback

When a transmitted signal is loops back and is retransmitted through a system, often causing a saturated and/or distorted result. This happens in audio when a microphone "hears" the sound coming from the speakers it's playing through, causing squealing distortion. This also happens when a camcorder "sees" the video signal from the video screen it's playing through, causing overly-bright or saturated color, "ghosts" and brightness of the picture.

FG Servo Motor

A frequency generator in the motor produces a signal dependent on motor rotation. This is compared to a reference signal and the motor is controlled so that the two signals are the same. Compared to an electronic governor motor, the FG motor has less speed deviation or drift and is less affected by temperature.

Fiber Optics

Process by which flexible glass fibers are used to conduct energy. It is valuable in the coupling of multi-stage image intensifiers.

Field

One half of a frame, consisting of either the odd or the even numbered lines, 60 fields are transmitted every second. flange back: The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.

Fill

The acoustic absorption added inside a speaker cabinet to suppress unwanted resonances and sometimes to increase the apparent volume of the cabinet.

Flange Back

The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.

Flying Erase Head

A feature available on selected VHS VCRs, on 8mm and Hi8 VCRs, and on camcorders. The unique design of these recording heads prevents electronic noise during videotape recording transitions, for glitch-free insert editing.

FM (Frequency Modulation)

Method of audio signal broadcast transmission used for radio.

f-number

The f-number indicates the brightness of the image formed by the lens, controlled by the iris. A smaller f-number means a brighter image.

Focal Length

The distance from the center of the lens to a plane at which point a sharp image of an object viewed at an infinite distance from the camera is produced. The focal length determines the size of the image and the angle of the field of view seen by the camera through the lens. That is the distance from the center of the lens to the pickup device.

Foot-Candle (FC)

It is the light intensity (illumination) of a surface one foot distant from a source of one candela. It is equal to one lumen per square foot. (1FC = 1 lm ft2). The foot-candle is the unit used to measure incident light.

Fp

The free-air resonant frequency of a passive radiator.

Frame

The total area of the picture which is scanned while the picture signal is not blanked.

Frequency-agile

means that the operating (modulation) frequency is adjustable to suit different applications.

Frequency Response

(Example, 30-20,000 Hz) Describes the audible range of frequencies that an audio system will reproduce. (Note: All else being equal, the lower the low number, the better the bass response and the higher the high number, the better the treble response.)

Front Porch

The portion of the composite video signal which lies between the leading edge of the horizontal blanking pulse and the leading edge of the corresponding synchronizing pulse.

Fs

The free-air resonant frequency of a speaker driver. The frequency at which an object tends to vibrate. For example, although a bell can be externally driven to vibrate at different frequencies, it will always naturally tend to vibrate at it's given tuned tone, or resonant frequency.

f-stop

A term used to indicate the speed of a lens. The smaller the f-number, the greater is the amount of light passing through the lens.

F3

The point at which the signal strength of a loudspeaker falls 3 decibels below the loudspeaker's rated SPL, as the frequency decreases.

Fully-Automatic Turntable

A turntable that, when turned on by the operator has all the necessary functions to lift the tone arm from rest post and place it on the lead-in groove and return it to the rest post when it reaches the record's end.

Full-Logic Controls

With this feature, all of the mechanical operations inherent to audiocassette receivers are controlled through a microprocessor chip, for smoother, faster, more accurate response and easier transitions from function to function.

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G

Gen-lock (Generator lock)

A method used to synchronize one or more cameras by external means such as: composite video, composite sync, horizontal or vertical sync.

Ghost

A shadowy or weak image in the received picture, offset either to the right or to the left of the primary image. It is the result of transmission conditions where secondary signals are created and received earlier or later than the primary signal.

GPS (Global Positioning System) SATELLITES

The array of geostationary satellites maintained by the U.S. government to beam back position-locating information as an aid to navigation. A vehicle navigation system integrates this information with a CD-ROM-based road map system to help drivers locate their position, straightline distance to their destination, and best route.

Ground

An electrical connection point that is common to either a metal chassis, a terminal, or a ground bus.

Ground Loop

Caused by different earth potentials in a system. Usually results in increased noise, interference and/or signal distortion.

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H

Headshell

A device for attaching the cartridge to the tone arm.

Hertz (Hz)

Pronounced "hurts". Unit of measurement for cycles of vibration per second. Also kHz or kilohertz (1000 hertz) and MHz or megahertz (1 million hertz).

Horizontal (hum) Bars

Horizontal bars, alternately black and white, which extend over the entire picture. They are known as venetian-blinds. They may be stationary or move up or down. They are often caused by approximately 60 Hertz interfering frequency or its harmonic frequencies.

Horizontal Blanking

The blanking signal that is produced at the end of each scanning line.

Horizontal Resolution

The amount of detail a TV picture delivers, measured in number of lines. The amount a viewer actually sees depends both on the source and the TV: Broadcast or cable signals deliver 330 lines of horizontal resolution; VCRs, 240 to 280; laserdisc players, 425. The horizontal resolution capability of many TVs and other video monitors exceed any of these sources.

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I

ISDN (Integrated Services Digital Network)

Digital phone lines that allow transmission of video signals via fastscan at speeds of 128Kb/second; used with terminal adapters.

Image Size

Reference to the size of an image formed by the lens onto the camera pickup device. The current standards are: 1", 2/3", 1/2" and 1/3" measured diagonally.

Impedance

The opposition which a circuit or component offers to the flow of electric current. It is expressed in ohms and is equal to the ratio of the effective value of the voltage applied to the circuit to the resulting current flow. In AC circuits, the impedance is a complex quantity that includes both resistance and reactance. In DC circuits, it is purely resistive.

Incident Light

The light that is falling directly over an object.

In-line

When one component is "inserted" into a circuit between other components.

Insertion Loss

The signal strength loss that occurs when a piece of equipment is inserted into a line.

Insulator

A protective coating used to inhibit conductivity between two conductive elements. Also, a shock absorber intended to prevent outside vibrations from exciting the turntable. Turntable cabinet feet are often constructed to act as insulators.

Integrated Circuit (IC)

A complex collection of semiconductors in a single component case.

Interlace

A scanning process where every other horizontal line is scanned in one field while the alternate lines are scanned in the next field to produce a complete picture frame.

Interleaving

A method used in alarms or activity detection which allows extra frames of video from alarmed cameras to be added to a time multiplexed sequence whilst a state of alarm exists.

IR (infra-red)

Literally means "below red". The band of frequencies just below the visible light spectrum.

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J

There are currently no terms defined in this section.

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K

There are currently no terms defined in this section.

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L

Lag

The image retention of an object after the object has been scanned. Sometimes, it causes smearing effect.

LCR Meter

Digital tester that measures inductance (L), capacitance (C) and resistance (R).

Le

Inductance. Usually specified for a voice coil of a speaker driver.

Line Conditioner

Processes AC voltages such that they are free of potentially harmful voltage variations that are inherent to many municipal electricity sources. The result is a consistent signal that is suitable for sensitive equipment.

Line Lock

To synchronize the field sync pulses, of an AC powered camera, to the frequency of the voltage input (line voltage). looping: A term indicating that a high impedance device has been permanently connected in a parallel to a video source.

Lithium Ion Batteries

A type of small rechargeable battery containing lithium, a light, highly reactive metal. Lithium ion batteries tend to have very long shelf life and can last for years in low-current applications. Typical uses include the powering of cellular phones, digital watch LCDs and memory backup in computers. An improvement over nickel cadmium batteries both in smaller size and lighter weight.

LNBF (Low-Noise Blocking Filter)

Mounted on a satellite dish to collect, convert and amplify the satellite signal reflected form the dish.

Looping

A term indicating that a high impedance device has been permanently connected in a parallel to a video source.

Loudness

Automatically adjusts bass enhancement depending on volume level.

Lv

The length or depth of a vented speaker cabinet's vent.

Lux

A unit of measuring the intensity of light. (1 FC [footcandles]= 10 lux).

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M

Magnetic Shielding

Speakers are magnetically shielded, preventing blurring and distortion of TV images.

Manual Iris Lens

A lens with a manual adjustment to set the iris opening (F stop) in a fixed position. Generally used for fixed lighting applications.

Matrix Switcher

A switcher able to route any of its (camera) inputs to any of its (monitor) outputs, they often includes telemetry control.

Mechanical Focus (back-focus)

The mechanical aligning of the imaging device with the focal point of the lens; it is most important on zoom lenses to be sure the image stays in focus throughout the zoom range.

Microfarad (µfd or MFD)

Unit of measure for capacitance. One millionth of a farad.

Millihenry (mH)

Unit of measurement for inductance. One one-thousandth of a Henry.

Minimum Object Distance (MOD)

The closest distance a given lens will be able to focus upon an object. This is measured from the vertex (front) of the lens to the object. Wide angle lenses generally have a smaller MOD than large focal length lenses.

Mms

The mechanical mass of a loudspeaker diaphragm assembly including the air load.

Modulate

To change or vary some parameter such as varying the amplitude of a signal for amplitude modulation or the frequency of a signal for frequency modulation. The circuit which modulates the signal is called a modulator.

Modulator

Often used to combine or convert one or more types of signal into a single "modulated" signal. Examples: CD changer RF modulator: modulates CD audio into an RF antenna signal to be heard with an FM radio. Also a UHF or VHF modulator converts separate audio and video signals into a single modulated RF antenna signal.

Monochrome

Having only one color. In television it is black and white.

Monochrome Signal

In monochrome television, a signal for controlling the brightness values in the picture. In color television, the signal which control the brightness of the picture, whether the picture is displayed in color or in monochrome.

MOSFET (Metal Oxide Semiconductor Field Effect Transistor) Power Supply

High-quality transistors that, when used in an amplifier, deliver high peak current with a shorter signal path and faster response time. This results in enhanced, more clearly defined audio, especially during louder music passages.

Moving-coil Cartridge (MC)

System in a cartridge in which a coil moves to generate an electromagnetic force. Features low impedance and special characteristics.

Moving-magnet Cartridge (MM)

System in a cartridge in which a magnet moves to generate an electromagnetic force. Easy-to-use and most common type.

MPEG1 (Motion Picture Experts Group format, version 1)

The earliest form of digital compression used by the DSS program providers to transmit audio/video information. The main advantage of MPEG technology is the transmission of more channels in what is normally a limited amount of space or band width.

MPEG2 (Motion Picture Experts Group, version 2)

The most advanced form of digital compression, currently used by the DSS program providers to transmit audio/video information. It continues to have all the advantages of MPEG1 but also helps improve certain picture quality transmission problems, e.g., motion tiling. The program providers started using this new compression technology in mid- to late-1995.

MTS (Multi-channel TV Sound)

An RF signal that carries more than one audio signal. Used for stereo audio, in many cases.

Multimedia

The presentation of multiple media at once. Usually associated with computer software and hardware that perform this function together, like games and CD-ROM packages.

Multiplex

To transmit two or more signals simultaneously on a single wire. Used in TV, CATV, video distribution (audio and video on the same line) and FM stereo broadcasting (left and right audio).

Multi-Room Distribution

The ability to distribute a DSS signal to multiple television sets. Currently the dual LNB DSS system is capable of sending the signal to any number of IRDs, while the single LNB unit feeds only one IRD.

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N

N/D (Neutral Density) Filter

A filter that attenuates light equally over the whole visible spectrum.

900-MHZ Reception System

Advanced cordless technology that transmits at a higher frequency band than that used by more common cordless equipment, for increased transmitter-to-reciever range and greater signal clarity.

Noise

Random spurts of electrical energy or interference.

Nickel Cadmium (Ni-Cad)

Combinations of these two elements can be used to hold a rechargeable amount of electricity. Most commonly used in rechargeable batteries and cells.

Nickel-Metal Hydride (NiMH)

Modern, high-capacity, rechargeable cell or battery. Often used in cellular phones and other devices where smaller size and weight are desirable without a loss in performance.

no

The reference efficiency of a loudspeaker with a half-space acoustical load.

NTSC (National Television Standards Committee)

National Television Systems Committee that worked with the FCC in formulating the standards for the United States color television system. Also a video format used in the US that uses 525 scanning lines in accordance with American television regulations.

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O

1-Bit D/A (Digital-To-Analog) Converter

Circuitry that translates the signal from a CD into an analog waveform using either a 1-bit pulse-density modulation (PDM) or 1-bit pulse width modulation (PWM) technique. In the case of PDM, signal information is represented by a series of pulses that have identical amplitude and duration but are either positive or negative. In PWM, the signal pulses all have the same amplitude but varying durations or widths. In both cases, the signal must be filtered before an analog waveform can be recovered.

1-Bit Dual D/A Converter

Since conventional multi-bit converters perform with the combined capabilities of many bits, they are prone to non-linear distortion. One bit converters, as used in most CD changers/players, process the signal by a signal bit at an extremely rapid rate. Since only one bit is operating, distortion is virtually eliminated and the unit is able to deliver sound that is true to the source.

Ohm

Represented by the Greek omega symbol. It is the unit of measurement for resistance and impedance.

Optical Digital Audio Input / Output

On selected components with digital audio, this feature allows a pure digital-to-digital connection between units for audio transfer entirely in the digital domain.

Oversampling

A digital filtering technique used in CD components: Extra data points are added to the audio read from a disc, creating a signal that is some multiple (usually two, four, or eight times) of the CD format's standard sampling frequency This process raises the frequency of any false information, which can then be removed by an analog filter.

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P

PAL (Phase Alternation by Line)

A common composite color transmission system used in Europe and elsewhere.

Parallel Push-Pull Circuitry

Amplifier circuitry that uses two output transistors each for the positive and negative halves of the signal cycle. Although it is costly, such circuitry greatly increases amplifier power handling and lengthens product life. It is found in selected audio equipment.

Passive

A non-powered element of a system.

Pe

The maximum electrical power that a speaker driver can handle before it is damaged, usually when the voice coil burns.

Peak-To-Peak

The amplitude difference between the most positive and the most negative excursions of a signal.

Pinhole Lens

Lens used for applications where the camera/lens must be hidden. Front of lens has a small opening to allow the lens to view an entire room through a small hole in a wall.

Piston

The moving portion of a loudspeaker. Includes the cone, dust cap, and surround.

Pitch Control

A control allowing speed changes of the record within a certain range, usually 6%-12%.

Pixel

The smallest unit of picture information in an electronic imaging device, such as a computer monitor, camcorder imager (CCD), or liquid crystal display (LCD). The larger the number of pixels that comprise such a picture, the clearer and more detailed the picture can be.

Polarity

Positive (+) and Negative (-) markings on a battery or other device that indicate the direction of flow of electrical current and voltage. The negative pole will have a surplus of free flowing electrons, where the positive pole will have a deficit of free flowing electrons.

Power

The rate at which electrical energy is applied to or taken from a device. It is expressed in terms of watts, milliwatts or microwatts.

Power Inverter

Converts DC voltage to AC voltage.

Pre-position Lenses

Zoom lenses which utilize a variable-resistor (potentiometer) to indicate zoom/focus position to the lens controller. After initial set-up, this allows the operator to view different pre-set areas quickly without having to re-adjust the zoom and focus each time.

Primary Cell

A cell that cannot be recharged. Must be replaced when discharged.

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Q

Q

The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a system.

Q't

The total Q of a loudspeaker's suspension with the load of the rear chamber in a 4th-order bandpass box.

Qec

The Q of a sealed (closed) loudspeaker at Fc considering only its electrical (non-mechanical) resistances.

Qes

The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a vented loudspeaker at Fs considering only its electrical (non-mechanical) resistances.

QL

The Q of a vented speaker cabinet resulting from all of the box losses (acoustic weaknesses).

Qmc

The Q of a sealed loudspeaker cabinet at Fc, considering only its mechanical (non-electrical) resistances.

Qms

The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a vented loudspeaker cabinet at Fs, considering only its mechanical (non-electrical) resistances.

Qtc

The Q of a sealed loudspeaker considering both mechanical and electrical resistances.

Qts

The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a vented loudspeaker considering both mechanical and electrical resistances.

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R

Radio frequency (RF)

Signals with a repetition rate above audible range, but below the frequencies associated with heat and light.

Random Interlace

A scanning technique commonly used in CCTV systems in which there is no external control over the scanning process. That is, there is no fixed relationship between adjacent lines and successive fields.

Range Finder

Used to determine the focal length needed and what the picture will look like on the monitor. The user looks through the device and adjusts the range finder to the desired picture. Numbers on the outside of the range finder indicate the focal length needed.

Raster

The rectangular pattern of scanning lines upon which the picture is produced. The illuminated face of the TV monitor without the video information present.

RCA Connector

Also known as "line-level", "A/V" and "phono" connector. Very commonly used in line-level audio applications as connectors for cables. Coaxial connector with a center pin and surrounding ring.

Re

The DC resistance of a speaker driver's voice coil.

Reflected Light

The scene brightness or the light being reflected from a scene. Usually it represents 5 to 95 percent of the incident light, and it is expressed in foot-lamberts.

Resolution

A measure of the ability of a camera or television system to reproduce detail. That is the number of picture elements that can be reproduced with good definition. It is a factor of the pickup device or the TV CRT characteristics and the video signal bandwidth.

Resonant Frequency [Fs]

The free-air resonant frequency of a speaker driver. The frequency at which an object tends to vibrate. For example, although a bell can be externally driven to vibrate at different frequencies, it will always naturally tend to vibrate at it's given tuned tone, or resonant frequency.

Retained Image

(image burn) A change produced in or on the target of the pickup device which remains for a large number of frames after the removal of a previously stationary light image and which yields a spurious electrical signal that corresponds to that light image.

RF (Radio Frequency)

Range of frequencies (10 kHz - 10 GHz) received through antennas.

RF Modulator

In auto sound, a device included with CD changer RF packages that converts the CD changer's audio signal to an FM radio station frequency for pickup by the car radio's tuner section. DSS systems with multi-room distribution unit use dual RF modulators to distribute two separate signals (from the receiver or another video source) so two separate programs can be viewed at the same time on two TVs in different rooms of the house.

RG-6

The number of the coaxial cable recommended when installing a DSS system. RG-6 is a larger cable with less signal loss and greater high-frequency transmission than the ordinary RG-59 coaxial cable.

Rms

The mechanical resistance of a loudspeaker's suspension losses.

RMS (Root Mean Square)

Technically speaking, RMS=.707 X (peak measured power). Basically it can be considered the "average" operating wattage.

Roll

A loss of vertical sync which causes the picture to move up or down on the TV screen.

RPM

Number of times an object rotates in one minute.

RS232

A commonly used computer serial interface.

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S

S/N (Signal to noise) Ratio

The proportion of true signal information to extraneous noise or interference that an audio or video unit delivers, usually expressed in decibels (dB). A higher number indicates a better S/N ratio. Measure of noise levels of a video signal: the higher the number the better.

Santoprene

Polymer (plastic) material that has similar weathering, flexibility and compliance to butyl rubber, but has lower recoil tendency (springiness) which can add unneeded resonances.

Satellite Speakers

Commonly used in home stereo systems along with a subwoofer. The subwoofer handles low frequencies up to 80-150 Hz, then the satellites take over and extend toward 20-30 kHz. This type of system eliminates the need for much larger speaker pairs that reproduce all of these frequencies, yet take up more room and are harder to hide in a room's decor.

Saturation (color)

The vividness of a color. It is directly related to the amplitude of the chrominance signal.

Scanning

The rapid movement of the election beam in a pickup device of a camera or in the CRT of a television receiver. It is formatted in a line-for-line manner across the photo sensitive surface which produces or reproduces the video picture. When referred to a video surveillance field, it is the panning or the horizontal camera motion.

Sd

The measured surface area of a speaker's piston.

Secondary Cell

A cell that can be recharged to its voltage rating by causing current to flow in reverse polarity, from positive to negative regions. Examples: Nickel-Cadmium (Ni-Cd), Nickel-Metal Hydride (NiMH), Litium Ion (Li-Ion) and lead-acid cells and batteries.

Semi-automatic Turntable

A turntable designed to automatically return the tone arm to the rest when it reaches the lead-out groove on the record.

Sens

The reference sensitivity of a loudspeaker measured at one meter as a sound pressure level. It was originally measured while driving a speaker with one watt, but is also measured driving a speaker with a constant 2.83 volts AC.

Sensitivity

(optical pickup device) The amount of current developed per unit of incident light. It can be measured in watts with the projection of an unfiltered incandescent source of light at 2870 K degrees to the pickup device surface area. It can be then expressed in footcandles.

Servo Motor

A motor with a built-in automatic speed control device to stabilize motor rotation. Shadow bar across the screen or as a tearing in the top corner of a picture.

Signal-To-Noise Ratio (S/N)

The proportion of true signal information to extraneous noise or interference that an audio or video unit delivers, usually expressed in decibels (dB). A higher number indicates a better S/N ratio.

Simplex (multiplexer)

A multiplexer that allows the user to look at multi-screen images or perform time multiplex recording. It cannot record multiplexer pictures while showing multi-screen pictures.

SIP (Single In-line Package)

A semiconductor design that consists of one row of pins.

Skating Force

Force drawing the tone arm toward the center when playing a record.

SPL (Sound Pressure Level)

The measured loudness of a sound. Often measured in decibels (dB) from one meter (1m) away from a speaker driver while it is playing a test tone that is being driven by one watt (1W) of power from the amplifier. (Example: 92 dB 1W/1m) Also measured from a speaker that is being driven with 2.83 volts of audio voltage. (Example: 92 dB 2.83V/1m)

Spot Filter

A small insert used in a lens to increase the f-stop range of the lens.

S-shaped Tone Arm

A tone arm shaped in a S-shape as opposed to a straight tone arm.

Stylus

Needle-like object that follows the record groove and picks up vibrations.

Subwoofer

A speaker designed to deliver extremely low-frequency sound (usually below 100 Hz). An active powered subwoofer utilizes its own built-in amplifier, separate from the amp used by other speakers in a system, for cleaner, more powerful bass response. Active subwoofers have built-in crossover circuitry to filter the low-frequency signal.

Super VHS (Super Video Home System)

A new format of high resolution VHS video recorders, capable of giving greatly improved picture if all features and special tapes are used. VHS compatible.

Surge Suppressor/Protector

component used to protect equipment that is sensitive to voltage variations (audio and computer equipment). Most often, suppressors/protectors will shut down completely at the introduction of a strong surge of power.

S-Video Input / Output

Special connectors that provide a sharper, higher-resolution picture by processing luminance and color signals separately to avoid interference. Available on high-resolution video sources, such as Hi8, ED Beta®, S-VHS VCRs, AV Laser players, DSS Digital Satellite System, and on selected "direct- view" and projection TVs.

Sync

Electronic pulses that are inserted in the video signal for the purpose of assembling the picture information in the correct position.

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T

Tap

used to split off a portion of the original signal for use elsewhere.

Tearing

A picture condition in which horizontal lines are displaced in an irregular manner.

Telemetry

A system utilizing control code transmitters and receivers. They can use either video cable or a simple twisted pair cable to send their information.

Termination

A non-inductive resistor that has the same resistance as the characteristic of the cable being used.

TFT (Thin Film Transistor) Active Matrix LCD Color Display

An LCD screen in which each pixel is powered by its own transistor, for images with purer, more distinct color and higher contrast ratio.

Timebase Corrector (T.B.C.)

An electronic circuit that aligns unsynchronized video signals before signal processing. Used in multiplexers and quad splatters.

Tone Arm

Device that holds the phono-cartridge, applies the necessary tracking force for tracing the grooves of the record.

Tracking

A zoom lens' ability to remain in focus during the entire zoom range from wide angle to telephoto position.

Tracking Force

Weight or force pushing the stylus down into the record groove.

T-S

Thiele-Small parameters, a certain collection of loudspeaker specifications named after the scientists who developed them.

24K Gold-Plating

Gold plating prevents oxidation of the plug's surface, minimizing the contact resistance and transmission loss that occurs over time.

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U

UHF (Ultra-High Frequency)

regulated band of frequencies used for broadcast signals. Used for TV (channels 14-63), two-way radios, wireless communications, instruments and other similar equipment.

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V

Vap

The volume of air having the same resistance to movement as the suspension of a passive radiator.

Vas

The volume of air having the same compliance, or ease of movement, as the suspension (surround, spider, etc.) of a speaker driver, i.e. a driver with a loose suspension will have a higher compliance and low Vas.

Vb

The internal volume of a vented speaker cabinet.

Vc

The internal volume of a sealed speaker cabinet.

VCP (Video Cassette Player)

Component that plays back pre-recorded VCR tapes.

VCR (Video Cassette Recorder)

Component that records and plays back RF signals used for TV and CATV broadcast.

Vertical Retrace

The return of the electron beam to the top of a television picture tube screen or a camera pickup device target at the completion of the field scan.

VHF (Very-High Frequency)

regulated band of frequencies used for broadcast signals. Used for TV (channels 2-13), two-way radios, wireless communications, instruments and other similar equipment.

VHS (Video Home System)

Probably the most popular format of home video tape equipment.

VHS Hi-Fi Stereo Audio

An audio recording and playback technology utilized in many VHS VCRs that delivers near CD-quality sound. Through a "depth multiplexing" technique, the audio signal is laid down beneath the video signal along the width of the tape instead of in a narrow band at the edge. This allows for inclusion of much more signal information, as well as the Dolby Surround sound encoding found on all major video movie releases.

Video Motion Detection

A system that uses the video signal from a camera to determine if there is any movement in the picture and set off an alarm.

Video Type Lens

An automatic-iris lens without an internal circuit to control the iris. All iris control voltages come from a circuit located within the camera.

Vidicon

A common type of camera pickup tube. It translates the effect of light striking its photo-sensitive surface into electrical impulses.

Voltage

Electromotive force (EMF), the internationally-accepted unit of measurement for the potential difference between a region with a surplus of free-flowing electrons (negatively charged) and a region with a deficit of free-flowing electrons (positively charged). Voltage induces current flow in a circuit.

VOM (Volt-Ohm Meter)

Analog electronic measuring device that measures voltage and impedance.

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W

Wow and flutter

Instantaneous variations in the rotational speed of the turntable platter. Also instantaneous speed changes in tape playback speed.

WRMS

Stands for the weighted root mean square, a method of using filters to give more "weight" to 4~6Hz modulations in the 3~4kHz region when making wow & flutter measurements since the ear is most sensitive to such speed fluctuations. Root mean square is a formula for deriving a virtual value from a fluctuating waveform. In contrast, sometimes wow & flutter is listed as a weighted peak (W peak value).

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X

Xmax

The maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field.

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Y

Yagi

Popular design for home radio/TV antennas.

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Z

Z

The nominal electromagnetic impedance of a loudspeaker or electronic system.

Zinc-carbon

Common, standard-output battery or cell using combinations of zinc and carbon compounds to create current flow. Made for light to medium duty devices with minimal or no motors or electrically-driven components. Known for low shelf-life, and leakage after electrical discharge. Examples: AA, AAA, C, D and others.

Zoom lens

A lens system that may be effectively used as a wide angle, standard or telephoto lens by varying the focal length of the lens.

Zoom ratio

The ratio of the starting focal length (wide position) to the ending focal length (telephoto position) of a zoom lens. A lens with a 10X zoom ratio will magnify the image at the wide angle end by 10 times.

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