Backbone: The low-voltage wiring that connects various electronic equipment together.

Bandwidth: A measure of the carrying capacity of a communications device, usually expressed in kilohertz (kHz) or megahertz (MHz).

Baseband: A band of frequencies and related equipment used to carry signals in an unmodulated form (i.e., in their original electric form, without any modification).

Bridge: A device that connects two networks together. Often found within Internet access devices like cable modems, where it connects a home LAN to the network of the Internet service provider and eventually to the Internet itself.

Broadband: A band of frequencies used to transmit voice, data, or video signals simultaneously. Use of broadband allows more information to be transmitted at the same time. Broadband is like a multi-lane highway.

CO: Incoming telephone lines.

Cable Modem: A high-speed Internet access device that uses the coaxial cable network of cable television providers to connect a home PC or LAN to the Internet.

Category 5e: A type of wiring used mainly to transmit data and voice signals.

CEBUS: Consumer Electronics Bus, an emerging standard for connecting consumer electronics devices to a home network. The most important part of the standard is the Home Plug and Play protocol, which allows compatible devices to identify and communicate with each other.

Computer Network: A system that transmits any combination of voice, video and/or data between computers. The network includes the network operating system in the client and server machines, the cables connecting them and all supporting hardware in between such as bridges, routers and switches. In wireless systems, antennas and towers are also part of the network.

Conduit: A plastic or metal pipe that is used to contain cable runs. It is often installed empty into new or renovated homes to allow easy running of new cables in the future.

Connected Home: A house that has been properly wired and designed to receive and distribute a variety of music, video and data signals throughout the house. Is also equipped to connect to services outside the home.

Daisy Chain: A method of connecting networked equipment such that each successive device in the network is connected in series from the previous device. This type of wiring is typically found in older telephone wiring installations, but it's not particularly flexible or reliable. Compare with Home Run.

Digital Subscriber Line (DSL): A dedicated digital high-speed broadband connection that is leased from the local phone company to provide a high bandwith, always-on internet connection.

Ethernet Local Area Network (LAN): A network of personal computers and peripheral devices configured to share information within the home. Ethernet is the most common computer network and is usually characterized by RJ-45 jacks.

Firewall: Hardware or software that prevents hackers from tampering with your computer and/or home network.

Futureproofing: The act of designing or installing a system that will meet the technological needs of a home today, as well as prepare it for future technologies.

Gateway: A software-driven device that receives a variety of information from the telephone company, cable company and internet service provider, distributes those signals to equipment in a way so that products of dissimilar networking protocols can communicate with each other.

Hardwired System: A system that uses its own dedicated cabling infrastructure to transmit commands to electronic devices.

High-Speed or Broadband Internet Access: A connection to the I

nternet that transfers data faster than a traditional telephone (dial-up) connection. The most common services are digital subscriber lines (DSL), cable modems or direct broadcast satellite (DBS).

High Speed Digital Internet: Worldwide, fast and secure surfing on the internet, e-commerce, e-mail and e-banking.

Home Network: Two or more computers interconnected to form a local area network (LAN) within the home. A home network allows computer owners to interconnect multiple computers so that each can share files, programs, printers, other peripheral devices, and Internet access with other computers.

Homerun: A wiring method that connects electronic components individually to a distribution hub (e.g., Start Network)

Hub: The central distribution point of a networking system where all wiring terminates. (Distribution Center/Box)

Infrared (IR): The part of the light spectrum just below the visible portion. Often used for wireless networked devices and remote controls in a home.

Internet Home Gateway: Acts as a router to direct the flow of digital signals throughout a building.

ISDN (Integrated Services Digital Network): A telephone system that allows two standard phone lines or medium-speed data networking over a single phone-line connection.

ISP: Abbreviation for Internet Service Provider. Internet service can be powered through the phone line, cable and power line.

Jack: A cable connector in the form of a receptacle, used with a plug to complete a cable connection. (also see plug).

LAN: (Local Area Network) LANs connect computers in a home, office or building. Each computer in a LAN can run its own programs, as well as access data on other computers on the LAN. The computers can also share printer and allow users on the LAN to communicate with each other. Most LANS use the Ethernet protocol.

Multimedia Outlet: An outlet that houses an assortment of cable, telephone/data and speaker jacks.

Modem: A device that converts a computer's digital signals into analog tones that can be carried over a telephone network. The name comes from the function, which is to MODulate and DEModulate these signals.

Panels: The metal or plastic enclosure which house and protect a microprocessor's circuitry, looks like an electrical circuit breaker box. Usually located in the home's basement.

Plug: The part of a connector system that goes into a jack to make an electrical connection. Typically, a plug is referred to as the male connector, while a jack is referred to as the female connector.

Prewiring: The practice of concealing wiring behind the wall of a home as it is constructed or renovated.

Protocol: A common language or specification used by devices communicating over a network.

Residential Gateway: A device that connects your home to the Internet via an Internet service provider.

RG-6: A type of wiring generally used to transmit video signals between devices. Often referred to as coaxial cabling.

Router: A device that connects different types of networks together. Is commonly contained within a gateway.

Satellite Dish-Based Internet: A high speed connection that uses a small disk antenna and digital transceiver to connect to the Internet.

Server: A computer program that provides services to other computer programs or other computers.

Shielding: A protective layer in a cable that prevents electromagnetic interference from outside sources.

Smart Homes: A relatively new term describing remote and in-house control of Internet enabled household appliances like refrigerators, heating systems, smoke and fire alarm systems.

Streaming: Streaming video is a sequence of "moving images" that are sent in compressed form over the Internet and displayed by the viewer as they arrive. Streaming media is streaming video with sound. With streaming video or streaming media, a Web user does not have to wait to download a large file before seeing the video or hearing the sound. Instead, the media is sent in a continuous stream and is played as it arrives. The user needs a player, which is a special program that uncompresses and sends video data to the display and audio data to speakers.

Structured Wiring: A multipurpose system of in-wall wire and cable linking a central distribution center/hub with multimedia outlets located in key rooms of a home (home office/den/study, kitchen, family/great room and each bedroom). This system delivers all the voice, data and video (cable, internet access, telephone, etc.) performance you need today while providing the capacity to handle tomorrow's technologies as well.

Surge Suppressor: A device that prevents damage to electrical or electronic equipment by isolating them from unexpected rises in current or voltage (e.g., lightning strikes).

Switcher: A device that sends data from one computer directly to another computer.

Switches: A central device that connects PCs at higher speeds than a hub.

Telephony: A powerful telephone connection using the Internet that offers security and good speech quality. You can also send and receive fax messages.

Terminate: Connecting a wire or cable to something, usually a piece of equipment or a jack or plug.

Uninterrupted Power Supply (UPS): A device that includes a battery that keeps a computer running several minutes after a power outage.

Universal plug and play: An initiative to simplify the interconnection of PCs, appliances, networks and services by extending plug and play to include networking.

UTP (Unshielded Twisted Pair): The cable used in most home telephone and data networks, this twisted-pair cabling contains no shielding to protect it from outside interference.

VoIP: Short for Voice Over IP. This refers to any technology offering voice telephony services over the Internet.

Voltage: The measurement of electrical force in a circuit, measured in volts.

X10: A proprietary technology that enables electronic devices to send and receive commands to and from each other via a home's standard electrical wiring.

CPU: Central Processing Unit. The brains behind a home control system, which can come in the form of a PC or a standalone processor.

Feedback: A feature of some keypads, sensors and home control systems that enables the status of electronic equipment to be communicated back to the homeowner.

Icons: Symbols or graphics that may represent electronic components, features, or functions. Icons are generally displayed on a touchscreen.

Macro, Mode or Scene: Any sequence of commands or functions issued by a single operation, such as pressing a button.

User Interface: Any tool, product or method (e.g., a touchscreen, a keypad or a remote control) designed to allow a homeowner to utilize another more complex product or system.

Aspect Ratio: The width-to-height ratio of a television screen. A standard-definition set has an aspect ratio of four units by three units (4:3), and is essentially a square. The aspect ratio of a high-definition set is 16 units by 9 (16:9), and is rectangular, like a movie screen.

Black level: The level of the darkest portions of the video. Blacks are just as important as colors when it comes to achieving a quality television picture.

CATV: Cable TV

Cabinet: Holds HT components on a pull-out rack.

Cable TV/ (Jacks): Wall plates/jacks with a threaded "F" connector commonly used to distribute a video signal from a VCR, cable television service or other video source to televisions over coaxial cable. These coaxial cables and jacks also can provide high-speed internet connectivity and PC networking services.

CRT Projector: One type of front projector, it consists of three tubes each putting out one color: red, green and blue. They offer brightness and detail, but are difficult to setup, and convergence is required about two times a year.

Direct-View: A TV set that uses a picture tube to create images.

Digital Light Processing (DLP): A technology that projects video images using a light deflecting off thousands of microscopic mirrors. Used in projector and rear projection televisions.

DTV (Digital Television): The next generation digital television system that has been approved by the Federal Communications Commission as a replacement for today's NTSC system. Allows a wide variety of video resolution and quality, including HDTV. Compare with NTSC.

DVD (Digital Versatile Disc or Digital Video Disc): A CD-sized digital disc used for playback of movies or music. The heir apparent to video cassettes.

DVD-R: A DVD player that works like a VCR (video cassette recorder), allowing users to record programming onto blank DVDs. There are five formats of recordable DVDs: DVD-R, DVD-RW, DVD+R, DVD+RW, and DVD-RAM. When shopping for a DVD recorder, look for a player that can handle as many formats as possible.

DVR: Stands for digital video recorder. These are players and recorders that store video on a hard drive, such as TiVo and Replay TV. New hybrid DVR/DVD players are emerging, allowing users to save on a DVD the television programs they've recorded onto a hard drive.

EDTV (Enhanced-Definition TV): It offers a picture that is crisper than standard definition television, but not as good as high definition. If you're upgrading your set, the experts recommend skipping EDTV and going straight to high-definition TV.

Flat screen/Flat panel: Flat screen refers specifically to the front of the television. Almost any television can be a flat-screen television, including a traditional CRT. Flat panel refers to thin models such as plasma and LCD sets, which resemble panels and can be hung on the wall. Also called flat displays.

Front Projection: A type of TV system in which the picture is projected onto a reflective screen. Front-projector sets are capable of producing an image of more than 12 feet diagonal.

HDTV: High-Definition Television. A TV or some other type of video source that's able to produce images digitally and with high resolution (officially defined as a resolution of 720 progressive or 1080 interlaced) for better clarity and realism. Designed to allow widescreen, film-quality video programming. The sound that comes through an HDTV is also digital.

High Definition Television (HDTV): A very high-resolution, high-quality television standard. See also DTV.

Home Theater Pre-Wire: Concealed speaker wires that could drive detached, in-wall or in-ceiling audio loudspeakers located to provide front left, center and right main channels, at least two side or rear channels and a subwoofer.

In-Wall Speakers Installed: Audio loudspeakers recessed in walls or ceilings, typically as part of a home theater or whole house audio system.

LCD: Liquid Crystal Display: A type of display that can be used for TV monitors; competes with plasma TVs as a flat display.

Lines of Resolution: A method of comparing the relative amount of detail of an image. (See Resolution)

Multi-Room In-Wall Audio/Video Wiring: Wiring inside the walls that could drive detached, in-wall or in-ceiling audio loudspeakers located in another part of a room or in other rooms in the house for home theater, music or paging/intercom functions.

NTSC: The standard by which TV is broadcast in the U.S. It has a theoretical maximum resolution of 525 lines. Also has an aspect ratio of 4:3.

Progressive scan/Interface scan: Since the advent of television, video pictures have been created by something called interlaced scan. This technology sometimes results in a noticeable flicker in the picture. Progressive scan reduces that flicker and gives a smoother picture.

PVR: (Personal Video Recorder): A device that uses a hard drive to record, stop and pause TV programs.

Rear Projection: A TV system where the picture is produced from behind the screen by red, blue and green electron guns.

Receiver: The guts of many home theaters. It has a decoder, audio/video switcher, AM/FM tuner, and an amplifier section all in one.

Resolution: A term associated with the number of lines that make up the vertical portion of the picture. The higher the number, the more detailed the picture is. If the resolution is too low, and the picture size too big, you get scan lines.

Satellite TV (Small Dish or Large Dish): Small dish or Direct Broadcast Satellite (DBS) is a subscription service that uses high-powered satellites to broadcast a digital TV signal to small 18" dish antennas. Large dish satellite TV, or a C-Band satellite system, uses lower powered satellites to transmit an analog signal to larger dishes.

SDTV: Standard Definition Television. A lower resolution than high definition, generally 480 lines per frame.

Streaming Audio/Video: A technique for transferring audio or video in a continuous stream while the entire signal is still being received.

Universal (Programmable) Remote: A IR or RF remote control that can be programmed to control multiple devices. Can be taught control signals from just about any other remote.

Alarm: When an alarm condition occurs, the keypad and external sounders sound, and the keypad displays the zone(s) causing the alarm.

Alarm System: A security system that combines various sensors, a central control panel, and signaling devices to warn of emergency situations such as a break-in, a fire, and flooding.

Annunciator: The element of an alarm system that alerts you to the status of the security system.

Armed: A system must be armed in order to detect an intrusion.

Automatic Dialer: When connected to a phone line, it dials emergency numbers automatically when an alarm is tripped.

Babysitter Code: This code can be used to arm the system, but cannot disarm the system unless the system was armed with this code. This code is typically assigned to someone ( such as a babysitter) who needs to arm/disarm the system only at certain times.

Central Monitoring Station: A facility operated by a security company that remotely monitors (over telephone lines or wireless links) a home security system.

CCTV: Closed-Circuit Television. A system consisting of a transmitter (a surveillance camera) that feeds one or more receivers (monitors) the pictures captured by the camera.

Duress Code: Intended for use when you are forced to disarm or arm the system under threat. When used, the system will act normally, but can silently notify the alarm monitoring company of your situation, if that service has been provided.

Entry Delay: Entry delays give you time to disarm the system when you re-enter through the designated entrance door. You must disarm the system before the entry delay period or the alarm will sound.

Event Logging: The system records various events in a history log, which can be viewed by the master user on an Alpha Display Keypad. Events are displayed in chronological order from most recent to oldest. When the log is full, the oldest event is replaced by the logging of any new event.

Exit Delay: Exit delays give you time to disarm the system when you exit through the designated entrance door. You must disarm the system before the exit delay period or the alarm will sound.

Fire Alarm: If installed, your fire alarm system is on 24 hours a day for continous protection.

Home Security System: A system designed to detect the presence of an intruder or other hazard in a residence or surrounding area. Most are professionally installed, will sound an alarm at the site, and report to a central station for a monthly fee.

Keyfob: A wireless transmitter, small enough to carry in a pocket, that can remotely arm and disarm a security system.

PIR: Passive Infrared. The technology used in most motion detectors. Infrared radiation emitted by the warmth of a human body is detected by a PIR detector.

Remote Monitoring: The ability to monitor a home from a remote location.

Scheduling: Provides end-user schedules which can control various types of events to start and stop at a specific time.

Security Panel: The part of a security system that receives information (signals from alarms, disarm command, etc.) and responds by transmitting a command to other equipment.

Sensors: The devices that notify a security system of trouble, be it a break-in, a fire or water in the basement.

Test Mode: Allows each protection point to be checked for proper operation. The keypad will sound a single beep every 30 seconds as a reminder that system is in test mode. If the test mode is inadvertently left active, it automatically turns off after 4 hours.

Voice Keypad: Voice keypads feature a voice message center that lets you record and playback one message (up to 2.5 minutes in length). Voice keypads also announce any faulted entry/exit or perimeter zone when Chime mode is on.

Zone: Specific area of protection.

AC: Appears when AC power is on.

Alarm: Appears when an intrusion has been detected and the system is armed (also appears during a fire alarm or audible emergency alarm). Accompanied by the protection zone in alarm.

Away Mode: All burglary zones, interior and perimeter are armed.

BAT: Low battery condition in a wireless sensor (if zone number displayed) or low system battery (if no zone number is displayed).

Bypass Mode: This appears when one or more burglary protection zones have been bypassed, but leaving the system armed.

Canceled: Appears when an alarm has been silenced by the Code + OFF sequence and will remain on until another Code + OFF sequence is keyed.

Check: Appears when a malfunction is discovered in the system at any time, or if an open is detected in a fire zone at any time, or a fault in a DAY/NIGHT burglary zone during a disarmed period. Accompanied by a display of zone number in trouble.

Chime Mode: Appears when the chime feature is activated.

Fault: Appears at anytime a malfunction is discovered in the system; or any time an open is detected in a fire zone; or when a fault in a day/night burglary zone is discovered during a disarmed period. Accompanied by a display of the zone number in trouble.

Fire: Appears when a fire alarm is generated. Accompanied by a display of the zone in alarm. A FIRE display also appears when a fire alarm is manually activated. Accompanied by a display of the fire emergency key zone number.

Instant: Entry delay is turned off: Lit with STAY = Instant mode. Lit with AWAY = Maximum mode.

Maximum: Same as AWAY, except entry delay is off.

Message: Appears when a message has been recorded and has not yet been played back.

Night-Stay: When specific interior zones are armed and all other bypassed, the NIGHT and STAY indicators are both on.

No AC: Appears when AC power has been cut off. System is operating on backup power.

Not Ready: Appears when burglary portion of the system is not ready for arming (due to open protection zones). The system is ready to arm when this message disappears and the READY indicator light comes on.

PH: Appears in place of the clock when the speaker phone mode is active.

Rec: Appears when the system is in recording mode.

Security Code: Your 4-digit security code assigned to you during installation. Use when arming and disarming system functions.

Stay: Perimeter burglary zones, such as protected windows and doors, are armed.

Test: Appears when the system is in test mode.

Addressable System Smoke Detector: System smoke detectors, which, in addition to providing alarm and trouble indications to a control unit, are capable of communicating a unique identification (address).

Air Sampling-type Detector: A sampling-type detector consists of piping or tubing distribution from the detector unit to the area(s) to be protected. An air pump draws air from the protected area back to the detector through the air sampling ports and piping or tubing. At the detector, the air is analyzed for fire particulate.

Alarm (Signal) Notification Appliance: An electromechanical appliance that converts energy into audible or visible signal for perception as an alarm signal.

Alarm Signal: A signal indicating an emergency requiring immediate action, such as an alarm for fire from a manual box, a waterflow alarm, or an alarm from an automatic fire alarm system, or other emergency signal.

Alarm Verification Feature: A feature of automatic fire detection and alarm systems to reduce unwanted alarms, wherein automatic fire detectors must report alarm conditions for a minimum period of time or confirm alarm conditions within a given time period, after being reset, to be accepted as a valid alarm initiation signal.

Annunciation: A visible and/or audible indication of system status.

Automatic Fire Alarm System: A system of controls, initiating devices and alarm signals in which all or some of the initiating circuits are activated by automatic devices such as smoke detectors.

Class A Circuit (Loop): An arrangement of supervised initiating device, signaling line, or indicating appliance circuits that prevents a single open or ground on the installation wiring of these circuits from causing loss of the system's intended function.

Class B Circuit (Loop): An arrangement of supervised initiating device, signaling line, or indicating appliance circuits, which does not prevent a single open or ground on the installation wiring of these circuits from causing loss of the system's intended function.

Combination Smoke Detector: A smoke detector that combines two or more smoke or fire sensing technologies.

Detector Coverage: The recommended maximum distance between adjacent detectors or the area that a detector is designated to protect.

Drift Compensation: The capability of a detector to automatically adjust its alarm sensitivity to compensate for any changes over time in the factory settings for smoke and/or fire detection. In analog systems, this may be done by the panel.

End of Line: A device such as a resistor or diode placed at the end of a Class B wire loop to maintain supervision.

End of Line Relay: Device used to supervise power (for four-wire smoke detectors) and installed after the last device on the loop.

False Alarms: An unwanted alarm caused by non-smoke contaminants such as dust or insects.

Fire: A chemical reaction between oxygen and a combustible material where rapid oxidation results in the release of heat, light, flame and/or smoke.

Flame Detector: A device that detects the infrared, ultraviolet, or visible radiation produced by a fire.

Four-wire Smoke Detector: A smoke detector which initiates an alarm condition on two separate wires (initiating loop) apart from the two power leads.

Heat Detector: A device that detects abnormally high temperature or rate of temperature rise.

Initiating Circuit: A circuit which transmits an alarm signal initiated manually or automatically, such as a fire alarm box, smoke, heat, or flame sensing device, sprinkler waterflow alarm switch or similar device or equipment to a control panel or any similar device or equipment which, when activated, causes an alarm to be indicated or retransmitted. An Initiating Device Circuit (Loop) is a circuit to which automatic or manual signal initiating devices are connected where the signal received does not identify the individual device operated.

Initiating Device: Any manually operated or automatically operated equipment which, when activated, initiates an alarm through an alarm signaling device.

Intelligent (Analog, Smart) System Smoke Detector: A system smoke detector capable of communicating information about smoke conditions at its location to a control unit. This type of detector typically communicates a unique identification (address) along with an analog (data) signal, which indicates the level of smoke at its location.

Ionization Smoke Detector: An ionization smoke detector has a small amount of radioactive material that ionizes the air in the sensing chamber, thus rendering it conductive and permitting a current to flow between two charged electrodes. This gives the sensing chamber an effective electrical conductance. When particles of combustion enter the ionization area, they decrease the conductance of the air by attaching themselves to the ions, causing a reduction in mobility. When the conductance is less than a predetermined level, the detector responds in a fire alarm condition.

Light Scattering: The action of light being reflected and/or refracted by smoke particles for detection by a photoelectric smoke detector. The action of light being refracted or reflected.

Listed: Equipment or materials included in a list published by an organization (e.g., Underwriters Laboratories) acceptable to the "authority having jurisdiction" and concerned with product evaluation, that maintains periodic inspection of listed equipment or materials and whose listing states either that the equipment or material meets appropriate standards or has been tested and found suitable for use in a specified manner. Note: The means for identifying listed equipment may vary for each organization concerned with product evaluation, some of which do not recognize equipment as listed unless it is also labeled.

Maintenance Condition: Method of providing annunciation of a smoke detector that it is out of its listed sensitivity range.

National Fire Protection Association (NFPA): An organization that administers the development and publishing of codes, standards, and other materials concerning all phases of fire safety.

Nuisance Alarm: An unwanted alarm caused by smoke from cooking or cigarettes.

Obscuration: A reduction in the atmospheric transparency caused by smoke usually expressed in percent per foot.

Particles of Combustion: Substances (products that either remain at the site of burning such as ash, or scatter as volatile products) resulting from the chemical process of a fire.

Photoelectric Smoke Detector: In a photoelectric light scattering smoke detector, a light source and a photosensitive sensor are so arranged that the rays from the light source do not normally fall on the photosensitive sensor. When smoke particles enter the light path, some of the light is scattered by reflection and refraction onto the sensor, causing the detector to respond.

Projected Beam Smoke Detector: In a projected beam detector the amount of light transmitted between a light source and a photosensitive sensor is monitored. When smoke particles are introduced into the light path, some of the light is scattered and some absorbed, thereby reducing the light reaching the receiver, causing the detector to respond.

Rate-of-rise Heat Detector: A device which will respond when the temperature rises at a rate exceeding a predetermined amount, usually 15° per minute.

Remote Maintenance Condition: NFPA 72 listed method of providing annunciation at the control unit that the smoke detector is outside of its listed sensitivity.

Smoke Detector: A device that detects the visible or invisible particles of combustion.

Smoothing Algorithms: A method of "smoothing out" a detector's interpretation of sudden, short-duration increases in obscuration within the sensing chamber, intended to reduce the occurrence of nuisance alarms.

Spot (Point) Detector: A device whose detecting element is concentrated at a particular location. Typical examples are bimetallic detectors, fusible alloy detectors, certain pneumatic rate-of-rise detectors, most smoke detectors and thermoelectric detectors.

Stratification: An effect that occurs when air containing smoke particles or gaseous combustion products is heated by smoldering or burning material and, becoming less dense than the surrounding cooler air, rises until it reaches a level at which there is no longer a difference in temperature between it and the surrounding air. Stratification can also be caused by forced ventilation.

Trouble Supervision: The ability of a fire alarm control unit (FACU) to detect a fault condition in the installation wiring, which would prevent normal operation of the fire alarm system.

Thermal Lag: When a fixed temperature device operates, the temperature of the surrounding air will always be higher than the operating temperature of the device itself. This difference between the operating temperature of the device and the actual air temperature is commonly spoken of as thermal lag, and is proportional to the rate at which the temperature is rising.

Two-wire Compatibility: Per NFPA 72, 1999 edition: "All fire detection devices that receive their power from the initiating device circuit or use a signaling line circuit of a fire alarm control unit shall be listed for use with the control unit."

Two-wire Smoke Detector: A smoke detector which initiates an alarm condition on the same two wires that also supply power to the detector.

Unwanted Alarm: Any false alarm or nuisance alarm.

Wireless Smoke Detector: A smoke detector which contains an internal battery or batteries that supply power to both the smoke detector and integral radio frequency transmitter. The internal power source is supervised and degradation of the power source is communicated to the control panel. On stimuli, the detector transmits a radio signal to a repeater or Fire Alarm Control Unit (FACU) that in turn generates a signal or status condition.

Airflow: When a vacuum cleaner is started, it creates a vacuum or an area of low pressure. Outside air rushes in to fill this vacuum. This rush of air or AIRFLOW is controlled and directed for maximum cleaning efficiency.

Watts: Represents the air power delivered by the power unit at various orifice sizes. The calculation is: Air Watts = Water lift X CFM/ 8.5 Maximum Air Watts is used by many in the vacuum industry to measure the amount of air power available to power air-driven power nozzles.

Amperage: Represents the amount of electrical current consumed by the motor during use. Ampere is to electricity, as gallon is to water; a measure of quantity.

CFM: A common unit of the measure of air moved by the vacuum fans.

Cyclonic Action
Some sytems use cyclonic separation. This differs from "filtered" central vacuums in the way fine particles are removed. While a filtered system uses a bag to catch these particles, a cyclonic system completely removes these particles by venting them outside. As dirt enters the canister, the air inside swirls like a tornado with the heavier debris falling to the bottom of the can, while the fine particles are vented outside. This prevents most of the dust from getting into the motor.

Dust Pan: Same as VacPan.

Electric Power Nozzle: Power head that cleans your carpet with an electrically driven motor that rotates the roller to loosen embedded dust and debris enabling the suction to capture the dirt and discard it into the dirt container.

Fans: The fan is the combination of blades that spin around to create the airflow to produce the vacuuming action. Units with two fans are called two-stage motors and units with three fans are called three-stage motors.

PVC: A common plastic polymer. The same material is used for both vacuum PVC pipe and plumbing PVC pipe.

Sealed Suction: Measures the maximum suction generated by the motor without airflow.

Stage: This indicates the number of sets of fan blades in a vacuum motor. Each fan - set of blades - increases the vacuum, or speed at which air is drawn through the system. The first fan starts air movement; the second increases it, and if there is a third fan it increases airflow still more. Thus the greater the number of fans the more powerful the vacuum.

Suction: The actual vacuum or water lift created by the fans in the vacuum motor.

Turbine Nozzle: Air driven head that cleans carpet by using the powerful suction of a central vacuum which rotates the roller to loosen dust and debris enabling the suction to capture the dirt and discard it into the dirt container.

VacPan: VacPan's are excellent for high traffic areas like kitchens. They offer the convenience of sweeping dirt right up to the VacPan and simply kicking the switch to activate the vacuum and remove the debris.

Vacuum Inches of Water: Same as Water Lift

Voltage (Volts): A measure of the electrical potential employed by a vacuum motor.

Water Lift: A classic measure of vacuum suction. The height to which water can be raised by a vacuum motor.

Absolute Phase: Correct polarity (direction of energy) over two stereo channels.

Absorption: The weakening of radio wave strength by losses in various materials

Absorption Trap: A parallel-tuned circuit made of either capacitors or coils used to absorb and reduce interfering signals.

"Academy" Filter: A high frequency filter used in some advanced home theater controllers to compensate for the overly bright soundtrack of many earlier films.

AC (Alternating Current): An electrical current that periodically reverses direction. The rate of change is known as frequency and is measured in Hertz (cycles per second). Standard wall outlets supply alternating current.

Acoustics: The science of sound.

Acoustic Baffle: Padding designed to absorb sound and diminish the reflection of sound waves, often used in the side walls near the front of a home theater.

Acoustic Suspension (a.k.a. Air Suspension): Type of loudspeaker system that utilizes a sealed enclosure.

ADC (Analog-to-Digital Converter): Circuit that converts analog (varying amplitude) signal to a digital (pulse type) signal.

AE (Audio Erase): The related circuit or the magnetic head that is placed ahead of the audio/control head. It functions to erase the audio track in preparation for a new sound recording.

AFC (Automatic Frequency Control): Circuit in a tuner that maintains a constant frequency regardless of changes in power supply or other conditions.

AGC (Automatic Gain Control): Circuit that maintains a constant luminance level regardless of input. In television, minimizes picture differences with changes in strength of incoming signals.

AHD (Audio High Density): System of digital audio recording on grooveless discs, employing an electronically guided capacitance pickup.

ALC (Automatic Level Control): Circuit that functions similar to AGC. As applied to audio, ALC action varies the gain to maintain relatively constant output signal over the normal range of sound levels.

AM (Amplitude Modulation): The type of transmission used in the standard radio broadcast band from 530 to 1705 kHz. A process which modulates the amplitude of a carrier wave according to a variation of the input voltage (signal).

Ambiance: Acoustical qualities of a room and its contents.

Ampere (AMP): Unit of measurement of electrical current.

Amplifiers Amplifier: A device that amplifies (boosts) the signals from source components (CD player, DSS receiver, etc.) and transmits the amplified signal to the speakers.

        Pre-amplifier: The first stage of an amplification system, which boosts the amplitude of a weak signal from a source (tuner, turntable, tape deck or CD player). It also may provide for tonal adjustment so that the signal may be fed into a power amplifier. Usually contains all audio controls.

        Power Amplifier: The second or final stage of an amplifier system, which regulates and increases low-level signals received from the preamplifier and feeds them to speakers.

        Integrated Amplifier: A component that combines a preamp and power amp in a single unit. An integrated amp combined with a tuner in a single unit is called a receiver.

Amplitude: Magnitude or strength of a signal or wave.

Analog: The old, non-digital way of producing images on a screen.

Analog VS. Digital: With analog recording and playback, a parameter such as the width of a movie soundtrack, the magnetic field on recording tape, or the side-to side swings of the groove on a phonograph record varies in a way that is directly analogous to the sound waves of the original sound. These variations are translated to a varying electrical voltage which ultimately causes the loud speakers' cones to move back and forth, recreating the original sound.

With digital recording and playback, points along the sound waves of the original sound are assigned numeric (or digital) values, which are represented as microscopic pits on CD's, magnetic pulses on tape, or microscopic dots on a digital movie soundtrack. When the recording or soundtrack is played back, the numeric values are converted back to the varying electrical voltage needed to drive the speakers. Digital soundtracks can be very high quality, but take up much more room than analog. Sophisticated techniques such as DOLBY AC-3 are therefore necessary to make multi-channel digital sound a practical reality.

Antenna: A device used to send or receive electromagnetic waves through the air.

Antenna Gain: Measure of antenna efficiency compared to a reference antenna, typically a 1/4 wave type.

Aspect Ratio: The shape of the image projected onto the screen, as denoted by units of width in relation to units of height. A 16:9 aspect ratio denotes a widescreen format, while a 4:3 aspect ratio denotes the TV-standard pan-and-scan format.

Attenuate: To reduce the level of a signal.

Audio Mixer: A unit that combines or blends several sound inputs.

Audio Spectrum: The full range of audio frequencies from the lowest to the highest. The audio spectrum humans can hear ranges from 20Hz to 20,000Hz (20 kHz).

AUX: Any nonspecific line input to a control unit or amplifier. May be used in connecting a tape deck or a CD player, for example.

Atmospheres: Background sounds, such as wind or traffic noise, which add to the reality of a scene. These sounds are sometimes recorded right at the shooting location, creating what is called a wild track for mixing into the soundtrack later.

Baffle: Provides an acoustic seal which prevents the air from the front of the speaker from mixing with the air from the back of the speaker. This prevents a loss of bass response.

Balance: Uniformity of frequencies. In home audio, a control that changes the relative volume of the left and right channels.

Band: A range of frequencies between two definite limits. Bands are assigned by the Federal Communications Commission for a specific use.

Band Pass Filter (BPF): A circuit, commonly having inductance and capacitance, that effectively passes a given range of frequencies above and below this range are attenuated.

Bandwidth: The frequency difference between the highest and lowest frequencies involved. The greater the bandwidth of a transmission channel, the more information it can carry.

Basket: The conical part of a speaker that holds together the magnetic structure, voice coil, cone and spider.

Bass: Low-frequency sounds of around 160 Hz and below.

Bass Frequency: The actual frequency of a crystal oscillator, usually then multiplied to some higher operating frequency.

Bass Reflex: Type of loudspeaker system that uses a port in its enclosure. The port admits external air to ensure that the back wave is in phase with the front wave.

Belt Drive: Turntable drive system whose platter is rotated by a belt attached to a motor pulley.

Biamping: Incorporating more than one power amp plus a crossover network for woofers and tweeters.

Bias: In tape recording, the high frequency signal applied to a tape to raise its frequency signal and response. Different tape formulations require different bias levels for optimum recording.

Bias Voltage: A fixed DC voltage which establishes the operating characteristic of a circuit element such as a transistor.

Binary: Numbers based on the power of 2, represented by zeros and ones. Commonly used for digital circuits.

Bipole: A speaker that radiates from front and back in phase.

Bitstream Converter: A one-bit or low-bit A/D and D/A over sampling conversion method developed by Philips in which the audio signal is represented through PDM (pulse density modulation) or time averaging at a frequency of 11.3Mhz.

Bi-Wiring: Connecting an amplifier to speakers using separate cables for woofers and tweeters.

Bridged Mode: Some amplifiers have the ability to be operated in a mode which inverts one channel of a stereo amplifier and places it in parallel with the other channel, in effect turning the amplifier into a mono unit.

Capstan: Rotating shaft that pulls tape at a constant speed during record and playback.

Capture Ratio:The ability of a tuner or receiver to select the stronger of two signals at or near the same frequency. Expressed in decibels, the lower the figure, the better.

Carbon Fiber: A strong synthetic material that is low in mass with excellent damping characteristics, used in the manufacture of tonearms.

Carrier: The basic or unmodulated radio wave.

Cartridge: Device to translate (transduce) styles motion to electrical energy in a phonograph, in three basic types - moving magnet, moving coil, induced magnet. A phono cartridge is sometimes called a pickup. Also, a tape container for automatic tape systems.

Cassette: Audio or video magnetic tape container having two reels. Consumers can insert it for recording or play back without handling the tape itself.

Cassette Deck: A component for recording and/or playing back audio signals using a tape cassette as the recording medium; does not contain a power amplifier. A single-bay cassette deck has one tape transport and magnetic tape head assembly. A dual-bay cassette deck has two transports and two tape head assemblies.

CAV (Constant Angular Velocity): Laser disc operating format in which the disc rotates at a constant speed during play. CAV permits special effects, but this format is somewhat wasteful of disc space.

CD (Compact Disc): A 4.5-inch plastic disc containing a digital audio recording that is played optically on a laser-equipped player. Has a 16-bit quantization rate to produce audio with high-fidelity sound.

CD Changer: CD player that can store and play more than one CD. Two types are available: carousel (with CD's arranged on a platter) and magazine (with CD's stacked in a container).

CD-G: Music CD plus graphics. In addition to audio, the disc has subcodes that carry text (such as liner notes, lyrics) and pixilated, computer-like graphics. A player with the proper adapter is needed to access the subcode information.

CD-I (Compact Disc Interactive): Sound and video are combined on a CD, the program of which depends on choices made by the consumer. Requires special playback units.

CD Player: A component designed to play compact disc (CD) recordings using a laser optical pickup. The signal from a CD player usually requires amplification. If the amplifier does not have CD inputs, then Tape In or AUX jacks can be used.

Circumaural: A type of headphone that surrounds the ear and almost totally isolates the listener from room sounds.

Clipping: Cutting off the signal peaks when too little amplitude is provided. This strains and can damage tweeters.

CLV (Constant Linear Velocity): Laser disc operating format wherein the rotational speed of the disc varies as the laser pickup travels from the inner edge to the outer edge of the disc. CLV is the operating format for Compact Discs.

Coloration: Cutting off the signal peaks when too little amplitude is provided. This strains and can damage tweeters.

Compact Stereo: A stereo system with tuner, amplifier, and often turntable, tape deck and CD player in the same housing, usually compact in size. Designed for non-portable use.

Component Stereo: A stereo system composed of separate elements, such as a tuner and amplifier, CD player and so on, each with its own power supply. Usually selected individually by the purchaser.

Cone: The surface that radiates sound in a direct-radiator speaker. Usually conical.

Crossover Frequency: The frequency at which a crossover network divides the audible spectrum and sends it to a speaker driver.

Crossover Network: A component that separates the frequency band and rotates each frequency range to the correct driver or amplifier.

Crosstalk: Undesirable interference noise caused by adjacent tracks. Results in loss of stereo channel separation due to leakage from one channel to the other.

CRT (Cathode-Ray Tube): Light sources used in directview TV's, computer monitors and some video projectors.

DAB (Digital Audio Broadcasting): Various digital systems designed to augment AM and FM analog broadcasting services.

DAC: (Digital-to-Analog Converter): A circuit that converts digital signals to analog (varying amplitude) signals.

Damping: The physical or electrical control of resonance.

Data Reduction: Any technique that reduces the amount of digital data required to represent a given amount of information. Data reduction enables large amounts of information to be easily and efficiently stored and transmitted.

DAT (Digital Audio Tape): A digital recording/playback format. Also used to identify tapes, recorders and players which use this format. The cassettes are about half the size of standard audio cassettes and usually hold up to two hours of recording time. The performance of DAT is very high.

DBS (Direct Broadcasting Satellite): Digital satellite systems with highly compressed signals, using 18 to 34 inch dishes.

DC (Direct Current): An electrical current that flows in one direction, including battery power.

DCC (Digital Compact Cassette): An alternative form of digital tape recording which, unlike DAT (digital audio tape), utilizes standard sized compact cassettes. DCC hardware also can play back conventional analog cassettes but analog machines cannot play or record DCC tapes.

Decibel (dB): Unit of measure for sound. A logarithmic expression of the relative loudness of sound. One tenth of a Bel.

De-Emphasis: A fixed equalization which typically rolls off high frequencies in the second step of a two-step noise reduction process.

Demagnetizer: A device that removes magnetism generated in tape heads as a consequence of playback and recording activities. Also called "Degausser."

Demodulation: The recovery of the original modulating information from a radio signal.

Detector: The circuitry that performs demodulation.

Deviation: The maximum frequency variation of an FM signal.

Diffraction: The bending or partial reflection of radio waves by metal objects.

Diffuser Panels: Wooden panels with recessed areas designed to diffuse sound throughout a room, often used on the rear wall of a home theater.

Digital Audio Server (DAS): A device that is equipped with a big hard drive on which to store, then replay through a stereo system a variety of audio content, including CDs, MP3s and Internet radio stations.

Digital Coaxial Output: An electrical output connection for the raw digital data stream.

Digital Recording: A system of recording in which musical information is converted into a series of pulses that are translated into a binary code intelligible to computer circuits and stored on magnetic discs. Also called "PCM" (pulse code modulation).

Digital Light Processing (DLP): An emerging video projection technology using thousands of tiny micromirrors that reflect light to create images on a screen.

Digital Signal Processing (DSP): Manipulation of signals for equalization compression/expansion and reverberation in the digital domain. Resulting sound may replicate the acoustics of a club, hall, church, stadium, theater, etc.

Dipole: An antenna which is made up of two active elements.

Direct Drive: A kind of turntable drive system. Its platter is also the rotor of the motor assembly, and its platter is rotated directly by the stator coils of the motor.

Directional Antenna: A TV or FM antenna that picks up signals better from one direction than another. Usually has two or more sections or elements for increasing directivity and must be oriented according to the signal being received.

Distortion: Inexact reproduction of an audio signal.

Diversity: Receiver design which picks up a radio signal simultaneously at multiple locations and intelligently switches or combines to yield the best continuous signal.

Dolby AC-3: The multichannel coding technology used for Dolby Digital film soundtracks, the new Dolby Surround AC-3 laser disc, the upcoming US High Definition TV system, and numerous cable and satellite applications.

Dolby, Digital (a.k.a. AC-3): The new name for the most popular 5.1-channel home theater sound system. Used to be called Dolby AC-3. Consists of front left/right speakers, a center speaker, left/right surrounds, and a Low Frequency Effects (LFE) channel, usually used with a subwoofer. Dolby Laboratories' newest film sound format, which provides five full-range digital sound channels plus a bass effects channel on 35mm prints, in addition to an analog track providing compatibility in all theaters.

Dolby, Noise Reduction: Complementary (record play) processing systems developed by Dolby Laboratories to reduce the noise inherent in recording media with minimal effect on the sound being recorded. Dolby NR includes the B-type, C-type, and S-type systems for consumer formats such as the audio cassette.

Dolby Pro-Logic: Most popular surround format. Almost any receiver nowadays has it. Uses matrixed surround in order to encode four channels of sound; left/right front channels, a center channel, and one surround channel. It is quite a common occurrence to see two speakers used for the one surround channel, however, as well as a subwoofer to supplement the speakers.

Dolby, Surround: The home surround sound format derived from Dolby's multichannel analog film sound format.

Dolby Surround AC-3: The new digital multichannel home format (page 13) derived from Dolby Digital film sound technology.

Dolby, Surround Pro Logic: The advanced form of home theater decoder that not only recovers the surround information from Dolby Surround programming, but also provides a center channel to keep dialogue firmly centered on the TV screen regardless of viewer location. Originally expensive, low cost decoder chips today make Pro Logic affordable in all kinds of home theater products, from A/V receivers to TV sets themselves.

Driver: Any sound-producing device; an individual speaker.

DTS (Digital Theater Systems) Surround: A six-channel surround-sound playback format being used for some movie soundtracks and music recordings.

Dubbing Stage: A specially-designed room resembling combined small movie theater and recording studio control room, used by film directors and sound engineers to create film soundtracks.

DVD (Digital Versatile Disc): The new 5-inch CD-like format used for storing movies with digital audio and video and interactive features. Future applications include DVD music titles and DVD-ROM for computers.

D-VHS (Digital VHS): A new videotape format due this fall, offering superb recording and playback of digital programming from digital broadcasts.

Dynamic Range: The range between the loudest and softest sounds a sound format or system can reproduce properly.

Effects: Sound effects, i.e., the non-musical elements on a soundtrack other than dialogue.

Efficiency: A measure of the percentage of electrical input that a loudspeaker converts into acoustic output. Most conventional home audio speakers are roughly 13%.

Electrostatic Speaker: A type of loudspeaker that creates sound via a vibrating surface that is electrically charged.

Emphasis: A process that boasts the high-frequency component of a signal for recording.

Enclosure: A box that holds a loudspeaker.

Envelopment: The characteristic of a listening space where the listener is surrounded by sound. Proper surround-channel envelopment of the audience is considered a very important characteristic of high-quality home and commercial theaters.

Equipment Closet: Main level of the house, holds the audio components of a whole house music system (amplifiers, receivers, CD players, satellite receivers, etc). Needs to have rear access.

Equalization: The action or circuitry which selectively adjusts the level of certain audio frequencies to compensate for deficiencies in the system. Also called "compensation."

Equalization Switch: Tapes come with different equalization or bias: normal, high or metal. This switch sets the tape deck's equalization to match that of the tape for best sound.

Equalizer: A device that changes the relative volume of individual frequency bands to suit personal tastes of the listener.

Fidelity: The degree to which an electronic product accurately reproduces sound. A high fidelity system delivers sound as close as possible to the original.

Field: A distribution of energy in space (i.e. electric, magnetic, sound).

Field Strength: The amplitude of a field at a given point, measured in volts per meter for electrical energy.

Filter: A device that allows certain parts of signals to pass.

FIP: (Function Indicator Panel): Front display device. Also called FDP for Fluorescent Display Panel.

Flutter: Sound distortion resulting from fairly rapid irregularities in the speed of a phonograph record or tape recording.

FM (Frequency Modulation): The form of modulation used for radio and television sound transmission in most of the world for satellite video transmission and for videotape recording. Less susceptible to interference than AM. The FM broadcast band covers 88 to 108 MHz.

Foley: The art of recreating incidental sound effects, such as footsteps or rustling clothes, synchronized with a moving picture. Named after one of its first practitioners.

Frequency: The number of complete oscillations per second of an electromagnetic wave. The pitch of radio signal that distinguishes it from another.

Frequency Agile: Having the ability to change frequencies, tunable.

Frequency Range: Measured in Hertz (Hz), the frequency range of an audio component is the range of frequencies it reproduces with a flat (linear) frequency response.

Frequency Response: A specification indicating how evenly a range of frequencies is reproduced by a component or sound system. Usually expressed as a specific range (45 Hertz to 17,000 Hertz, for example) and combined with a plus/minus decibel figure indicating how evenly the frequencies in that range are reproduced. Hertz is synonymous with cycles per second.

Frequency Synthesized Tuning: An FM tuning method that employs a reference quartz crystal oscillator for exceptional tuning accuracy often better than 0.003 percent.

Front Channels: The path along which the sound travels to the front speakers. Home theater surround-sound systems generally have three front channels for left, right and center speakers.

Front End: Tuning or radio frequency section of a radio or TV set.

Front Projection: The type of video display device used to project an image onto a facing screen, found in most very high-end home theaters.

Gain: Degree of signal amplification, expressed in decibels.

Graphic Equalizer: A device that permits altering the tonal balance of an audio component/system at several frequency levels, usually offering from 5 to 12 adjustments.

Ground: A conducting path between an electrical circuit (or equipment) and the earth (or some conducting body serving in place of the earth).

Guard Band: The space between tracks on tape that keeps crosstalk to a minimum.

Harmonic Distortion: Distortion that occurs when an audio component adds unwanted overtones to the original music tones.

HDTV (High-Definition Television): Super high-resolution television broadcasts as part of Digital TV services which began in 1998.

Head: The electronic component that makes contact with magnetic tape to convert electricity to magnetism (for recording) or magnetism to electrical signals (for playback). Heads are used to record, erase or play tape signals.

Headroom: Temporary output level beyond a component's continuous rating which it can handle for short periods of time without overload.

Head Switching: Circuits that, in conjunction with 30Hz -squarewaves (switching pulses), prevent the head from producing an amplified output signal that is not on tape.

Hertz (HZ): The unit of frequency equal to one cycle per second (cps) One kilohertz (kHz) equals 1,000 cps; one megahertz (MHz)equals 1 million cps.

Heterodyne: To combine signals of various frequency in a manner that produces additional signals at frequencies which are sums and differences of the original frequencies.

High Frequency: In audio, the range from about 5 kHz to20 kHz.

Home Automation: The integration of electrical systems to operate under one convenient interface, often also applied to more convenient operation of various home theater components.

IC (Integrated Circuit): An electronic circuit in the form of a microminiature silicon chip, consisting of thousands or even millions of transistors (and other components), usually about the size of a fingernail or smaller.

IF (Intermediate Frequency): A lower radio frequency (typically 10.7MHz) found in the middle stages of a receiver.

IM (Intermodulation): Frequencies produced by combinations of other frequencies in non-linear devices (also IMD: Intermodulation distortion).

Imaging: Extent to which a stereo system reproduces the location of instruments or vocalists as they were during recording.

Impedance: Electrical resistance (measured in ohms) to the flow of alternating current. The lower the number of ohms, the more efficient a loudspeaker and the more power that can be used to drive it.

IR (Infrared): A form of light.

Infrared Repeater System: There is a device which is designed to receive an infrared signal at one location, convert it to an electrical signal for re-transmission by wire to a second location where the signal is then converted back to infrared.

Insertion Loss: A drop in signal level caused by the addition of a component to the audio signal path.

Insulator: A material that stops the flow of current.

Integrated Amplifier: A component that combines a pre-amp and power amp in a single unit. An integrated amp combined with a tuner in a single unit is called a receiver.

Inverse Square Law: Mathematical relationship in which one quantity is inversely proportional to the square of another quantity (i.e. signal strength decreases according to the distance squared).

Jitter: Fluctuations in a digital signal resulting from speed variations during playback.

Laser: (Light Amplification by Stimulated Emission of Radiation): A tightly focused beam of light used to play the signals stored on laser video discs or CD recordings.

Laserdisc: Twelve inch movie disc software with digital audio and analog video, which may be replaced by DVD.

LCD (Liquid Crystal Display): Technology used to create video displays on flat, thin screens, also used in remote control devices such as touchscreens.

LCRS (Left, Center, Right, Surrounds): The standard channel and speaker configuration for commercial and home theater systems.

LED (Light Emitting Diode): A solid-state device that glows when current passes through it.

Limiter: A circuit which limits the maximum level of a signal.

Line Doubler: A video enhancement component, often used with front projection systems, appearing to double the number of scan lines to sharpen the image and increase brightness.

Line-Level Signals: Audio signals from a tuner, CD player or tape deck that are at a level too low to drive speakers directly. Line-level signals must be amplified by a preamplifier and power amplifier (or receiver) before being sent to speakers.

Linear Drive: An analog tonearm for turntables or laser scanner for CD players that moves in a straight line instead of pivoting from a center point.

Linearity: The straightness of a frequency response carve as an indication of true or accurate sound reproduction.

Loss: Decrease in signal strength during transmission, propagation or reception.

Low Frequency: Frequency below 160 Hz.

Low-Mass: Low-weight phono cartridge or tonearm or tonearm/cartridge combination devised for operation with minimal downward pressure on record grooves.

Magnetic Field: The area surrounding a magnet, which is affected by it. The field created by magnets in telephones, electric motors, TV's and other consumer electronic products are usually only felt for a foot or two around them. Because video and audio tape are magnetic media, it is best to keep tapes away from magnetic fields.

Magnetic Shielding: The area surrounding a magnet, which is affected by it. The field created by magnets in telephones, electric motors, TV's and other consumer electronic products are usually only felt for a foot or two around them. Because video and audio tapes are magnetic media, it is best to keep tapes away from magnetic fields.

Magnetic Tape: A ribbon of thin plastic coated with magnetic material used in both audio and video tape decks.

Matrix(ing): The process of mixing two distinct signals with specific phase and amplitude relationships to form one signal so that the original components of the total signal can be separated at a later time.

MD (MiniDisc): A 2.5-inch optical disc encased in a sleeve for use in audio MD players/recorders.

Memory: Circuitry and devices that hold information, in electrical or magnetic form, such as a preset radio station frequency in a frequency-synthesized tuner or programmed tracks in a CD player.

Metal Tape: Tape whose coating is of iron particles; noted for its wide dynamic range and frequency response capability.

Mid-Bass: Frequencies between 40 Hz and 80 Hz.

Mid-Range: The audio frequencies between treble and bass.

Mini System: An audio system that is downsized.

Mix: The blend of dialogue, music and effects which comprises a film's soundtrack. Also, when used as a verb, the process of assembling and balancing these elements electronically, thereby creating the final soundtrack.

Mixer: A unit that combines or blends several sound inputs.

Modulation: Variation of a wave parameter (such as amplitude or frequency) to carry information.

Matrixed Surround: Term used to describe the process to make Dolby Pro-Logic compatible material. It fits four channels of sound into a space meant for two channels.

Multimedia Center: A combination of several audio, video and data sources that offers homeowners access to a variety of content through one device or system.

Multiroom, Single-Source System: A system that is able to distribute a single source of music to multiple rooms.

Multiroom, Multisource System. A system that is able to distribute different sources (CD player, DSS receiver, etc.) to multiple rooms simultaneously.

Rear Speaker: The term wrongly applied to surround speakers.

Sources: CD players, DSS receivers, AM/FM tuners and other equipment that produces music or video.

Speaker Selector: A device capable of distributing the output of a single amplifier to multiple speakers.

Subwoofer: This is a separate speaker used to handle the bass of movie soundtracks, and can be used with the Low Frequency Effects channel in the new digital sound formats.

Surround Sound: The popular term used to describe an experience where the sound 'surrounds' you. This is best achieved using surround-encoded material, a receiver, and surround speakers.

Surround Speaker: Buy these to best achieve the surround sound effect. This type of speaker diffuses the sound so as to make it harder to discern where the sound is coming from.

Tweeter: The part of a speaker that produces mid to high-frequency sounds.

Watt: A measurement of power to drive speakers. More watts is typically better than less.

Woofer: The part of a speaker that produces a spectrum of low- to mid-frequency sounds.

Zones: Individual sections of a house (for example, the sleeping area, the living area, the basement) that can be managed autonomously. Speakers in one zone might receive music, for example, while another zone receives no music.

10BaseT: IEEE 802.3 Ethernet LAN standard, with data on Cat 3 or Cat 5 twisted Pair (TP) wiring, with a data range of 10 Mbps.

100BaseT: IEEE 802.3 Ethernet LAN standard, with data on Cat 5 twisted Pair (TP) wiring, with a data range of 100 Mbps.

AC: Alternating Current. All electrical outlets in a home operate at 120V, 60 Hz.

Amplifier: An active electronic device to increase the amplitude of a signal.

Analog: An analog signal is a wave-shaped signal that represents information in a continuously variable and directly measurable quantity, such as voltage. The standard telephone signal is an analog signal.

Attenuator: A passive device to reduce the amplitude of a signal.

AWG: American Wire Gauge. AWG is the standard gauge for measuring the diameter of copper, aluminum and other conductors.

Baseband Video: Raw video signal from a single video source (e.g. camera or VCR). Typically appears at a yellow phone jack labeled "Video".

Broadband Video: Modulated video signal. Usually comes from an antenna or CATV feed and contains many channels. Also applies to output of modulators. Typically carried on coax cable and connects to F-connector labeled "CATV/Antenna".

Cat 5, 5e & 6: Category 5, 5e & 6 is a performance class for cables, jacks, connectors and interconnection components. The performance level and testing is specified in the EIA/TIA 568A Commercial Wiring Standard.

CATV: Community Antenna Television, commonly referred to as cable TV, is a TV signal received over cable.

CCTV: Closed Circuit Television, such as a security or safety camera.

CEBus: Consumer Electronics Bus, a residential consumer product communications standard developed by the Electronics Industry Association (EIA).

Coax: Coaxial Cable. A center conductor is surrounded by a dielectric, a shield and an outer insulator. The signal is unbalanced, and the shield provides noise immunity. Generally used for broadband TV transmission.

Digital: Information that is encoded in a series of "1"s and "0"s.

DBS: Digital Broadcast Satellite

Decibel (dB): A logarithmic ration used to indicate signal strength. Gains and losses expressed in dB should be added and subtracted (not multiplied).

Insertion Loss: The loss of signal due to attenuation or power splitting through a passive device.

IR: Infrared, commonly used in remote controls.

ISDN: Integrated Services Digital Network, residential or commercial digital telephone service.

Jack: The female connector, usually mounted in a faceplate or on equipment. Accepts a plug.

Jumper Cord: A short, connectorized cable which interconnects two jacks, e.g. from equipment to a wall plate.

LAN: Local Area Network. The most common LAN today is 10BaseT network.

Mbps: Megabits (millions of bits) Per Second.

NIU: Network Interface Unit (or NID: Network Interface Device). A small box, usually mounted on the outside wall of the house, which is the boundary between the phone (or cable) company wiring and the house wiring. Also called the demarcation point.

Off-Air TV: Broadcast Television received by an antenna.

Plug: A male connector, usually on a cable. Plugs into a jack.

POTS: Plain Old Telephone Service. Also referred to as "analog" telephone service. Includes voice, fax, and modem.

T568A: Designation for the pin assignments in a modular jack. Most appropriate for use in the residence.

TP: Twisted-Pair Wire. A twisted pair consists of two insulated copper wires twisted together. Cat 5 cable is 4 twisted pairs in a common sheath. The twists provide balance and noise immunity. Generally used for analog voice and digital (LAN) transmission.

UTP: Unshielded twisted pair.