The following is a general vocabulary list of terms that are commonly used throughout this web site.  If you don't understand a term while reading a section of the site, here is where you go to find out more about the term.  If you are having trouble with a term and don't see it listed here, feel free to e-mail us at our feedback section and we'll write you back with a full explanation.

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100baseT - an IEEE Ethernet standard allowing 100Mbits per second baseband data over twisted-pair cabling.

10baseT - an IEEE Ethernet standard allowing 10Mbits per second baseband data over twisted-pair cabling.

66 Block - a telephone wire terminal device that is used to join several wire pairs.

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A / D (Analog to Digital) - converts analog voltages into a digital representation.

A / V - industry term for Audio / Video or Audio / Visual.

Adjacent Channels - two television channels having video carriers 6 MHz apart, or two FM channels having carriers occupying neighboring channel allocations.

AGC (Automatic Gain Control) - a circuit that monitors the high pilot and automatically controls amplifier gain and keeps the output level constant with changing input levels.  Main control over the high frequencies.

Ampere (Amp or A) - the unit of measurement for electrical current delivered a wire of specific diameter.  One ampere is the rate at which current will flow through a resistance of one ohm when under a pressure of one volt.  If a wire is too small for the amount of electricity it must carry, it will overheat and blow a fuse.

Amplification - the process of increasing the strength (current, power, or voltage), of a signal.

Amplifier - a device used to increase the signal voltage, current, or power.  It may contain several stages in order to obtain a desired gain.

Amplitude - the maximum instantaneous value of an alternating voltage or current, measured in either the positive or negative direction.

ANSI (American National Standards Institute) - the principal standards development body in the United States.   ANSI is a non-profit, non-governmental body supported by over 1000 trade organizations, professional societies, and companies.  It is the United States' member body to ISO.

Antenna - a device consisting of spaced elements that are used to receive broadcast signals.  It may be either broadband or single channel.

Architecture - identifies the requirements and applications of a network.

Arrester - a device placed from phase to ground whose nonlinear impedance characteristics provide a path for high-amplitude transients.

ASCII (American Standard Code for Information Interchange) - the standard code consisting of 7-bit coded characters (8 bits including parity check), used to exchange information between data processing systems, data communication systems, and associated equipment.  The ASCII set contains control characters and graphic characters.

Attenuation - the loss of signal strength during transmission of a signal, light beams or light wave.  In cables, it is generally expressed in decibels per length.  The opposite of gain.

Attenuator - a passive device made up of a network of resistors used to reduce voltage, current or power (signal strength) delivered to a load.

Automation - automatically controlled operation of an apparatus, process, or mechanical or electronic devices that take the place of human organs of observation, effort, and decision.

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Ballast - a magnetic coil that adjusts current flow through a fluorescent lamp providing the necessary current surge to start the lamp and maintain even current flow for continuous operation of the lamp.

Bandwidth - the data-carrying capacity of a transmission medium, usually measured in hertz (Hz).

Barrel Connector - an adapter used to connect two coax-type connectors of the same gender.

Branch Circuit - any one of the complete routes for carrying electric current usually emanating from the main line.

Breaker - short for circuit breaker.

Bridge - connection point between two network media, such as radio frequency (RF) to twisted pair or fiber optic to coax.

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Capacitance - a cable's unique ability to store an electric charge and to resist sudden changes in the magnitude of that charge (voltage).

Category 5 - four twisted pairs of high-capacity wire enclosed in an insulated sheath (or jacket).  Handles telephone signals for telephones, faxes and modems, plus video and data signals.   Transfers data at 100Mbits per second.

CATV - originally an acronym for Community Antenna Television, now generally used to mean cable television.  An RF distribution system that distributes television broadcast programs, original programs, premium programming and other services using a network of coaxial cable.

CCTV (Closed Circuit Television) - a system of monitors within an internal network such as an office, school or home with one or more cameras, that does not receive an outside signal or feed.

CEBus (Consumer Electronic Bus) - an open standard that specifies requirements for communications between and interoperability of products in a home or light-commercial environments.  It specifies the required communications protocol and network object and product models and follows the seven-layer OSI protocol stack.

CES - Consumer Electronics Show put on by the EIA.

Channel - a single path for communications.  Channels may be one or two-directional, but only one communication can take place at one time.  Channels are separated by conducting path, frequency, time and other things.

Circuit Breaker - a device used to open and close a circuit by non-automatic means and also to open a circuit by automatic means when a predetermined level of current passes through it.  Circuit breakers can be reset.

Closed Circuit - a system in which television signals are transmitted over cable or telephone lines without being broadcast through the air.

Coaxial Cable - cable used to carry television and FM signals with characteristic impedance of 75 ohms.  It has a center wire, insulation, a tubular conductor (such as conductive pipe, braid, or foil), and more insulation, all centered or "coaxial" about the center.

Conduit - a protective pipe through which wiring is run.

Consumer Electronics (CE) - electronic equipment for the mass consumer.

Controller - a device or group of devices that service to govern, in some predetermined manner, the electric power delivered to the apparatus to which it is connected.

CPU (Central Processing Unit) - often used for control.

Crosstalk - the interference caused when signal frequencies from one line are coupled onto an adjacent line.  May cause distortion of data in the system.

Current - the flow of electricity in a circuit, measured in amperes.

Cycle - one complete positive and one complete negative alternation of a current such as a complete revolution of a 60 Hz sine wave from zero degrees back to zero degrees.

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DA (Distribution Automation) - technology to control electrical distribution by utilities.  This includes automatic meter-reading, outage detection, etc.

Daisy Chain - a wiring method where each termination point is wired in series from the previous jack.  Daisy chain is usually not the preferred wiring method, since a break in the wiring would disable all jacks "downstream" from the break.  See also Home Run.

DC (Direct Current) - an electrical current flowing in one direction only and constant in value.

Digital - refers to use of binary code in storage and transmission of data.  In recording audio and video data, the images are discrete, non-continuous codes.  Provides signal reproduction with little noise or distortion.

Distortion - any difference between the wave shape of the original signal and the wave shape after the signal has passed through the distribution system.  See also Interference.

Dolby Pro Logic - advanced surround sound system for the home using two front speakers, two rear-channel speakers for ambiance reproduction and a front center channel speaker for dialog and "logic steering".

Dolby Stereo - standard sound reproduction used in most theaters that uses a minimum of six channels.

Dolby Surround - a system designed to duplicate Dolby Stereo in homes using three channels and four speakers.

Downstream - the transfer of data from outside the house to inside the house.

DVD (Digital Versatile Disc) - an optical disc system the size of a CD-ROM capable of storing an entire movie.   The technology uses MPEG-2 compression and typical capacity for these discs is 4.5 GB, or about 133 minutes of digital video.

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EEI (Edison Electrical Institute) - a non-profit trade association for the investor-owned utilities.  Its charter includes lobbying for the benefit of the electric utilities as well as promoting the industry.

EEPROM (Electrically Erasable Programmable Read Only Memory) - an IC (integrated circuit) chip, capable of storing software instructions or data and retains that information when power is removed.   The information in an EEPROM can be erased by exposing it to an electrical charge.

Encryption - scrambling of digital signals to prevent unauthorized monitoring of the message over the airwaves.

EPROM (Erasable Programmable Read Only Memory) - an IC (integrated circuit) chip, capable of storing software instructions or data and retains that information when power is removed.  Erasing is done by exposure to ultraviolet light.  New information is loaded into the EPROM using a PROM programmer or PROM burner.

Equalizer - a device used on RF distribution Systems to compensate for cable or amplifier loss and provide a flat overall frequency response.

Ethernet - an IEEE standard for computer data communications.  A local area network used for connecting computers, printers, workstations, terminals, etc. within the same building.   Ethernet operates over twisted wire and over coaxial cable at speeds up to 100Mbps.   Ethernet LANs are being promoted by DEC, Intel and Xerox.  Compare with Token Ring.

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F Connector - a threaded connector used for coaxial cable and usually crimped onto the coaxial cable allowing the cable center conductor to become the connector center contact.

FCC (Federal Communications Commission) - the United States standards-setting body for communication industries.

Feedback - the return of a portion of the output of any process or system to the input.

Fiber Optics - plastic or glass cable that carries a large capacity of information using light beams (modulated light waves) and is immune to electrical noise, lightening, and induced voltages.   Data, expressed as pulses of light rather than electrons, is transmitted by lasers or other devices.  Fiber-based systems are well suited for high-volume and broadband communications.  A pair of hair-thin strands can carry the same volume of information as 32,000 pairs of copper communications cables.  Fiber is costly and requires sophisticated electronic equipment.

Fuse -  a protective device inserted in series with a circuit.  It contains a metal that will melt or break when current is increased beyond a specific value for a definite period of time.

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GA (gauge) - identifies the size of a conductor such as wire.  The lower the number the bigger the wire.

Gain - a measure of amplification of a device, usually expressed in dB and at the highest frequency of operation.

GND (Ground) - a home's ground wire(s) or grounding rod.

Ground Block - connector that passes the RF signal through with minimum loss while providing a means of attaching a ground wire to the drop cable typically near the entry to the home.  Grounding is accomplished by either a special ground rod or connection to the water system.

Ground Fault - an undesired path that allows current to flow from a line to ground.

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HANA (Home Automation & Networking Association) - a trade association for installers and manufacturers of home automation products and systems.  Formerly known as HAA (Home Automation Association).

HDTV (High Definition Television) - the new digital standard for enhanced picture for TV broadcasting that will dramatically increase the number of HRLS, providing a much sharper picture even if the image is several feet wide.  HDTV requires signals to be broadcast in HDTV format.

Home Automation - result of installing communicating microprocessor-based products and systems in homes.

Home Run - a wiring method that connects each outlet or sensor directly to the distribution or control panel instead of several outlets / sensors on a continuous loop.

Home Plug 'N Play - an interoperability specification for consumer products based on CAL language developed by the CEBus Industry Council usable over any network protocol.

Home Systems - network of smart products, intelligent subsystems, and home controllers that can communicate for the purpose of control or information dissemination.

Hot Wire - the ungrounded conductor wire in a cable that carries electrical current or load, usually identified by black or red insulation but may be any color other than white, gray or green.

House Code - an alpha character (A-P) setting on an X-10 device that you can use to indicate an area or zone within the home.  This code setting is combined with a Unit Code to uniquely identify the X-10 device.

HVAC (Heating, Ventilation, and Air Conditioning) - a system that provides heating, ventilating, and / or cooling within or associated with a building.

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I / O - input / output

IDTV (Improved Definition Television) - a system that electronically doubles the horizontal resolution lines producing a picture somewhere between HDTV and current broadcast television.  IDTV uses standard television signals.

IEEE (Institute of Electrical and Electronic Engineers) - an international professional society that issues its own standards and is a member of ANSI and ISO.

Impedance - the total opposition offered to the flow of an alternation current.  It may consist of any combination of resistance, inductive reactance, and capacitive reactance, inductive reactance, and capacitive reactance.  It is measured in ohms and the lower the ohm value the better the quality of the conductor.

Incandescent Lamp - an electric lamp consisting essentially of a glass or quartz bulb evacuated or filled with an inert gas in which a filament, commonly of tungsten, gives off light when it is heated to incandescence by an electric current.

Intelligent Subsystem - a system that incorporates the information available from another product / system or several other products / systems to achieve enhanced benefits for its own category.  The key to the categorical definition of "intelligent subsystem" is the primary purpose of obtaining and using outside data.  If the systems primary design is to use the data from other products for its own category's benefit, it's an intelligent subsystem.

Intercom - intercommunication system, as in between two or more rooms.

Interference - the inhibition or prevention of clear reception of broadcast signals or the distorted portion of a received signal.

Inverter - takes DC power and converts it into AC power.

IR (infrared) - the part of the invisible spectrum that is contiguous to the red end of the visible spectrum and that comprises electromagnetic radiation of wavelengths from 0.8 to 1000 microns.

ISDN (Integrated Services Digital Network) - a technology allowing access to the telco switching network that facilitates high speed control and communications using existing telco facilities.

Isolation - the amount of separation or loss between two terminals of a device or between two components.

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Jack - a receptacle used in conjunction with a plug to make electrical contact between communication circuits.  A jack is the female component of a plug / jack connector system and may be standard, modified or keyed.

Jacket - the outside covering of a cable.

Joules - the energy that a device is capable of directing away from the load in the event of a spike, surge or transient.

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KHz (Kilohertz) - a term meaning 1000 cycles per second.

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LAN (Local Area Network) - short distance network, typically within a building, used to link together computers and peripheral devices such as printers under some form of standard control.

Laser Disc - a disc that has video images encoded into it and read by a laser.  Similar to the storage of digital audio information on a compact disc (CD).

LCD - Liquid Crystal Display.

LED (Light Emitting Diode) - a semiconductor light source.

Lightning Arrester - a device used to pass large electrical impulses to ground.

Load - the amount of electric power delivered or required at any specified point or points of a system.

Load Management - management of the electric utility load to insure adequate power supplies as well as adequate usage of capacity deficiencies or transmission limits.

Load Shedding - disconnecting or interrupting the electrical supply to a customer load by the utility usually to mitigate the effects of generating capacity deficiencies or transmission limits.

Lux - the IS (international system) unit of illumination; one lumen uniformly distributed over an area of one square meter.

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Matching Transformer - a device, often called a balum, which converts between a 75-ohm impedance and a 300-ohm impedance.

MHz (megahertz) - a unit of frequency denoting one million Hertz.  Usually refers to the upper frequency band on a cabling system.

Mixer - a device that will "mix" the input signals together producing the two original signals and their sum and difference frequencies.

Modem - a device that converts a computer system's digital information into analog information and transmits it over a telephone line.  Another modem must be used when the information is received to convert the information back from analog to digital.

Modulate - placing information onto a higher frequency carrier by means of varying the frequency, amplitude, or phase adjustment.

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NEC (National Electrical Code) - a set of rules and regulations plus recommended electrical practices that are put out by the National Fire Protection Association and generally accepted as the building wiring standard in the U.S.

Network - ties things together.  Computer networks connect all types of computers and computer-related devices; terminals, printers, modems, door entry sensors, temperature monitors, etc.

Neutral - one of the conductors of a three-phase wire system.  Sometimes called the return conductor, it carries the entire current of a single-phase circuit and the resultant current in a three-phase system that is unbalanced.

Neutral Wire - the grounded conductor wire in a cable that completes a circuit by providing a return path to the source.  Always identified by white or gray insulation.

Noise - any unwanted signal that affects a wide or narrow band of frequencies.

Normally Closed - a circuit or switch in which the contacts are closed during normal operation.  Breaking or opening the circuit triggers an alarm signal.

Normally Open - a circuit or switch in which the contacts are open during normal operation.  Shorting or closing the circuit triggers an alarm signal.

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Occupancy Sensor - a control device that senses the presence of a person in a given space, commonly used to control lighting systems and HVAC.

OEM (Original Equipment Manufacturer) - company that develops, produces and sells consumer and computer hardware.  Often, an OEM sells to a second company that sells the hardware under its own name.

Off-hook - when the handset is lifted from its cradle, it is off-hook and completes an electrical loop, thus signaling the central office that is wishes dial tone.

Off-peak - periods of relatively low electric system demands.

Ohm - the unit of measurement of electrical resistance.   One ohm of resistance will allow one ampere of current to flow when under an electrical pressure of one volt.

On-hook - when the telephone handset is resting in its cradle and only the bell is active, it will ring if a call comes in.

Outlet - a single-piece wire / cable termination assembly (typically on the floor or in the wall), containing one or more connections.

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PBX (Private Branch Exchange) - a small, privately owned version of the telephone company's larger central switching office.

Peak Load / Peak Demand - the greatest amount of power required by the customers of an electrical system at a particular instant of time, measured in watts.

Phase - wire for electricity.  Most house are wired with two 120 VAC phases.

Photocell - a device that produces an electric reaction to visible radiant energy (light).

PLC (Powerline Carrier) - the transmission of communication signals across utility powerlines or existing home wiring.  Frequencies may range from 8 kHz to 200 kHz and above and power levels are normally low (in the 1 to 20 watt range).  The advantages of these systems include their ability to send signals over very long transmission lines (more than 100 miles) and their reliability.  However, they are limited in the amount of information they can transport because of narrow bandwidths.  Their low-frequency signals are severely attenuated by capacitor banks and transformers and can be overcome.

Polarity - describes which side of an electrical circuit is the positive and which is the negative.

Port - an entrance or exit from a network or a computer interface where a modem can be attached.

Programmable Controller - a device that controls the operation of electrical equipment (such as air conditioning units and lights) according to preset time and schedules.

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Quick Clip - an electrical contact used to provide an insulation displacement connection to telecommunication cables.

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Raceway - a protective shield installed over surface wiring for safety and physical protection of the wires.

RCA Jack - standard jack for audio component connections, has a pin in the center and teeth around the outside.

Receiver - the part of a communications system that converts electrical waves into visible or audible form.

Relay - an electromechanical switching device that can be used as a remote control.

Repeater - a device that amplifies and regenerates signals so they can travel further.

Residential Gateway - a device that allows consumer premise equipment connected to in-home networks to access and use service from any external network regardless of media.

Retrofit - a modification to an existing building.

RG59 Cable - a coaxial cable used for broadband video applications with a 22-gauge center conductor.  Uses standard "F" connectors for video equipment connections.

RG6 Cable - a coaxial cable used for broadband video applications with a 20-gauge center conductor, allowing a higher bandwidth than RG59 cable.   Uses standard "F" connectors for video equipment connections.

RF (Radio Frequency) - generally refers to data modulated over a high-frequency electromagnetic waves carrier for wireless transmission, the division of the radio spectrum.

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SEC (Securities and Exchange Commission) - federal regulatory body with authority over public utility holding companies.  In recent years, the SEC has allowed these companies to enter non-core businesses in greater numbers.

Sensor - a device that is designed to produce a signal or other indication in response to an event or stimulus within its detection area.

Serial Interface - an I / O port that transmits data 1 bit at a time (in contrast to parallel transmission, which transmits multiple bits simultaneously).  RS-232C is a common serial signaling protocol.

Series Wiring - see Daisy Chain

Service Panel - the equipment that controls the main supply of electrical current to a building and usually consists of circuit breakers, disconnect switches or fuses located near the point of entrance of the service to the building.

Setback Temperature - a temperature set point selected for the cooling mode that is higher than the design set point for energy conservation purposes.  In the heat mode, the set-point temperature will be lower than the heating design set point for the purpose of saving energy.

Shielding - protective coating that helps eliminate electromagnetic and radio frequency interference.

Signal Collision - caused by two or more X-10 transmissions on the power lines at the same time, essentially canceling one or both transmissions.

Signal Strength - the intensity of an RF signal measured in volts (V), millivolts (mV), microvolts or dBmV.

Slave - a mechanism under control of the actions of a similar mechanism.  Normally used with a PLC 3-way RF receiver switch or relay device.

Smart Products (for the home) - products that include some processing power within themselves and have the ability to send / receive data or control messages to / from another product.  All use some digital control to automate some product function and some send control messages but most cannot both receive and send information at this time.

Snow - a large quantity of random noise in a television picture that results from a poor signal to noise ratio.

Spike - a momentary increase in electrical current that can damage electrical equipment.

Spread Spectrum - a signaling technique where the AC energy transmitted by a device is spread over a range of frequencies rather than remaining concentrated at one frequency (such as an AM radio station).  CEBus uses spread spectrum techniques on the power line and radio frequency devices.

Structured Wiring - a planned and organized method of residential low voltage wiring allowing for efficient hook-up and future changes and additions.

Subwoofer - a loudspeaker that reproduces the very low sounds usually in the range of 20Hz to 1000 Hz.

Super VHS - video tape player that combines with compatible S-VHS tape to produce images featuring an increase in HRLs and a sharper picture.

Surge - a rapid rise in current or voltage, usually followed by a fall back to a normal level.

Surround Sound - a system that separates the various components of the sound track, then disperses them to speakers placed around the room.   Four to five speakers are incorporated, and surround sound processor is used to create the effect.  For example, voices could come from behind the screen while other sound effects could come from beside or even behind the viewer.

Systems Integration - having intelligent subsystems that communicate with each other and act upon the information shared.

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TAD - Typical Answering Device.

TCP / IP (Transmission Control Protocol / Internet Protocol) - a set of communications protocols to connect different types of computers over networks.

TELCO - an Americanism for telephone company.

Telecommunications - any transmission, emission, or reception of signs, signals, writings, images, and sounds, or information of any nature by cable, radio, visual, optical or other electromagnetic systems.

Terminate - to connect a wire conductor to something, typically a piece of equipment.

Tone Dial - a push-button telephone dial that makes a different sound for each number pushed.  The technically correct name for tone dial is Dual Tone Multi Frequency or DTMF.

Topology - the physical or logical layout of links and nodes in a network.  These include star, ring, and bus configurations.

Touchscreen - a visual display terminal screen that responds to instructions as the user touches the screen.

Tuner - a device for tuning an electronic circuit or device used to select signals at a specific radio frequency for amplification and conversion to sound.

Tweeter - a loudspeaker designed to reproduce high-pitched or treble sounds in the range of 4Hz to 20 kHz.

Twisted Pair - two insulated copper wires twisted around each other to reduce induction (thus interference or noise) from one wire to the other.   The twists, or lays are varied in length to reduce the potential for signal interference between pairs.  Several sets of twisted pair wires may be enclosed in a single cable.  In cables greater than 25 pairs, the twisted pairs are grouped and bound together in a common cable sheath.

Two-Way System - a distribution system that delivers signals to the customer (downstream) and back to the head end (upstream).

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UL (Underwriters Laboratories) - a privately owned company that tests to make sure that products meet safety standards.  UL also administers a program for the certification of Category Rated Cable such as Cat 5 cable.

UL Listed - signifies that production samples of the product have been found to comply with established Underwriters Laboratories requirements.   The manufacturer is authorized to use the Laboratories' listing marks on the listed products that comply with the requirements.

Unit Code - a number (1-16) setting on an X-10 device, combined with a House Code to uniquely identify the X-10 device.

Universal Remote Control - a remote that can control all elements of a home theater system including audio / video and sometimes even extending to functions such as lighting, HVAC, and draperies.

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V (Volt) - the unit of measurement of electrical force.   One volt will force one ampere of current through a resistance of one ohm.

Voice Activation - commands entered into a computer dictionary carried out when the computer recognizes the controller's voice.

Voltage - pressure at which a circuit operates.   Expressed in volts.

Voltage Regulator - controls the output voltage and eliminates voltage sags and swells in the input voltage that lasts from 15 milliseconds to one-half second.

Voltmeter - an instrument designed to measure a difference in electrical potential in volts.

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Walk-Test - testing a space protection sensor to identify its coverage pattern by walking through the protected area.

Watt - the unit of measurement of electrical power, or rate of work.  One watt represents the amount of work that is done by one ampere of current at a voltage of one volt.

Whole House Controller - a computer-based system dedicated to integrating and managing all home electronics systems.

Woofer - a loudspeaker designed to reproduce bass frequency.

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X-10 - home automation protocol that uses existing home wiring to broadcast a 5-volt 212 kHz msec burst perfectly timed to cross the 60 Hz AC power cycle.  An X-10 message includes a start code, letter code and number code.

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No "Y" terms yet.

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Zoned Control (HVAC) - a method of designing and controlling the heating, ventilation and air conditioning (HVAC) system of a residence so that living areas can be maintained at a different temperature than sleeping areas using independent thermostats.

Zones - smaller subdivisions into which larger areas are divided to permit selective access to or control of some zones.

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