Aggregate Throughput: A measure of the theoretical maximum amount of data a network or other communications system can carry in a given time frame. Basically a total summation of all data rates of all simultaneous transmissions possible at one instance on the system. For example if a system could support 5 simultaneous transmissions of 2 Mbit/sec.

Amplitude Modulation (AM): A technique whereby the voltage level or amplitude of a carrier is varied in order to transmit digital or analog information.

ANSI: The American National Standards Institute sets standards for the US computer industry. ANSI participates in defining network protocol standards.

Antenna: That part of a radio communications system intended to radiate and/or collect radio frequency energy.

Antenna Gain: A relative measure of an antennas ability to direct or concentrate radio frequency energy in a particular direction or pattern. Typically measured in dBi or dBd.

Anti-Jam: The ability of a spread spectrum system to resist interference or jamming signals.

Attenuation: The loss or weakening of a signal through a transmission line, transmission component, or signal path. Usually refers to loss in signal amplitude or signal power, and is typically measured in decibels (dB).

Attenuator: A component that reduces the magnitude of current, voltage, or power of a signal in transmission between points.

Bandpass Filter: A signal filter designed to pass a continuous range of frequencies, while attenuating frequencies which are both above and below that range.

Bandwidth: The width of the operating or transmission channel of a system. The difference expressed in Hertz (between the highest and lowest frequencies of a band).

Baud: The number of signal level changes per second. Each signal level contains one (or more) bits of information.

Bias-T: An in-line device which couples DC power onto a coax cable enabling both DC power and RF signals to travel through the same cable.

Bilateral Amplifier: A device which amplifies an RF signal in both the transmit and receive directions.

BPSK: Binary Phase Shift Keying - Digital DSB suppressed carrier modulation.

Bridge: Typically used to describe a component of a communications network which spans the network from one physical medium to another, such as from a wired Ethernet to Wireless.

Bulkhead Connector: A connector type which is designed to be mounted through a panel or wall.

Carrier Sense Multiple Access/Collision Detection (CSMA/CD): A technique of transmitting over a local area network where only one transmitter may use the line at one time.

Cavity Filter: A popular type of RF filter which employs a hollow resonant cavity to resonate out unwanted frequencies.

Cellular: A wireless communications network architecture which employs "cells" or modular coverage areas, typically serviced by a “cell site”, and usually provides hand-off capability between cells for roaming devices. (See also hand-off and roaming)

Ceramic Filter: A type of radio frequency filter which utilizes a ceramic-dielectric material in its construction.

Chip: In spread spectrum, the time it takes to transmit a bit or single symbol of a PN code (a single element of the spreading code).

Circular Polarization: The radiation of radio energy in a circular pattern similar to sound wave propagation, or the circular ripples in water caused by a stone being dropped into it.

Coaxial Cable, Coax: A concentric two-conductor cable in which one conductor surrounds the other, separated by an insulator.

Code: A digital bit stream with noise-like characteristics. In Spread spectrum the term code refers to the pseudo-random code used to control the modulation technique used to spread the carrier.

Code Division Multiple Access (CDMA): A technique used to increase channel capacity which is associated with spread-spectrum systems. Typically each user is given a different pseudo-random spreading code. To communicate with a particular user, the sender must select the code assigned to that user. This technique can permit many users to operate simultaneously on the same frequency.

Collisions: In network systems, when two nodes transmit simultaneously, causing destruction of a data packet’s information.

Compression: In RF amplification, an amplifier is said to be “in compression” (distorting) when the output is no longer a linear representation of the input signal, typically at the operational limits of the amplifier.

Connectivity: The ability of a device to communicate with other devices through a data communications medium.

Corner Reflector: A type of antenna which typically employs a bent piece of sheet metal to serve as the reflector element.

Correlator: The receiver component that demodulates a Spread Spectrum signal. Basically used to measure the similarity of two signals. Sometimes referred to as a "de-spreader" in direct sequence systems.

CW: Continuous wave. An analog signal which is always "on" (100% duty cycle).

Data Encryption Standard (DES): An encryption standard issued by the National Bureau of Standards.

dBd: Decibels relative to a dipole. (See also Decibel & Dipole)

dBi: Decibels relative to an isotrope. (See also Decibel & Isotrope)

dBm: Decibels (dB) relative to one milliwatt. (See also Decibel)

dBW: Decibels (dB) relative to one Watt. (See also Decibel)

Decibel (dB): A logarithmic representation of magnitude relationships commonly used in radio and sound measurement.

Demodulate: To convert a modulated signal back to an unmodulated "baseband" signal.

De-spreading: The process used by a correlator to recover narrowband information from a spread spectrum signal.

Digital Signal: A signal that is composed of two energy levels (on and off). Digital signals are used by computers to transmit data. The pattern of the level changes represents individual bits of information.

Digital Signal Processor (DSP): A specialized microprocessor which contains hardware features specifically tailored to the processing of signals.

Diplexer: A device which combines two transmitters onto one transmission line.

Dipole Antenna: The most common wire antenna. Length is equal to one-half of the wavelength for the frequency of operation. Fed by coaxial cable.

Direct Sequence (DS): A spread spectrum modulation technique where a pseudo-random code directly phase modulates a carrier, increasing the bandwidth of the transmission. The resulting signal has a noise-like spectrum. The signal is despread by correlating with a pseudo-random code identical to and in synchronization with the code used to spread the carrier at the transmitter.

Diversity: Used to describe a receivers ability to select between two receive antennas, typically cross polarize (one horizontal and one vertical). This feature is useful for operating in areas susceptible to the affects of multi-path interference.

DPSK: Differential Phase Shift Keying - a simplified BPSK where only data transitions are transmitted.

Driver: A low level software module that controls an input/output port or external device such as a keyboard or monitor. Driver are used to control wireless network interface cards, for example.

Dummy Antenna/Dummy Load: A device which serves as a transmitter's antenna without radiating radio waves. Generally used to test transmission components. The device dissipates the radio energy in the form of heat.

Duplexer: Simultaneous receive and transmit on one transmission line. The receiver filter passes the receive frequency while rejecting the transmitters frequency. The transmitter filter passes its frequency while attenuating the receive frequency.

Duty Cycle: A percentage of the time "on" (transmitting) versus the time "off" (not transmitting).

Effective Isotropic Radiated Power (EIRP): A measure of a signal's absolute power in a particular direction (see ERP), but relative to an isotrope rather than a dipole.

Effective Radiated Power (ERP): The product of the transmitter peak envelope power, expressed in Watts, delivered to the antenna, and the relative gain of the antenna over that of a half wave dipole antenna.

EMI/RFI: Electro Magnetic Interference/Radio Frequency Interference. Broad spectrum noise or interfering signals.

Encryption: Modification of a bit stream so that it appears random. Encryption is used for security purposes. The sender and receiver must both employ the same encryption method.

Ethernet: Ethernet is a type of wired network that supports high speed communications among devices over a coaxial cable.

Ethernet Address: An Ethernet address is a six-part hexadecimal number in which a colon separates each part (for example, 8:0:20:1:2f:0). This number identifies the Ethernet board installed in a PC and is used to identify the PC as a member of the network.

ETSI: The pan-European communications regulatory standards board.

Fade Margin: The loss in signal along a signal path, measured in dB, caused by environmental factors such as terrain, atmospheric conditions, etc.

Federal Communications Commission (FCC): A board of commissioners, appointed by the President, having the power to regulate wire and radio telecommunications in the United States.

Feedhorn: That part of a parabolic or grid reflector antenna which contains the driven element.

Feedline Transmission Line: A system of cable or other conductors that connects an antenna to a radio.

File Server: A process running on a computer that provides access to files on that computer to programs running on remote machines.

Filter: A device used to block or reduce signals at certain frequencies while allowing others to pass through.

Frequency: The number of cycles of alternating current in one second, measured in Hertz (Hz).

Frequency Hopping (FH): A spread spectrum modulation technique where the transmitter frequency hops from channel to channel in a predetermined but pseudo-random manner. The signal is de-hopped at the receiver by a frequency synthesizer controlled by a pseudo-random sequence generator synchronized to the transmitter's pseudo-random generator.

Frequency Modulation (FM): An analog modulation technique whereby the frequency of a carrier is varied to encode information.

FTP: File Transfer Protocol, the FTP application is used to provide file transfer services across a wide variety of network systems. Usually implemented as application level programs, FTP uses TELNET and TCP protocols. The server side requires a client to supply a login indentifier and password before it will honor requests.

Full-duplex Transmission: A channel that allows transmission in two directions at the same time. For example, cellular telephone service is typically full duplex.

Gain: The relative increase in power or magnitude of a signal typically measured in decibels.

Gas Tube Arrestor: A type of lightening arrestor which employs a gas discharge tube, which is a component containing a small amount of gas.

Grid Antenna: A type of antenna which employs an open-frame grid as a reflector, rather than a solid one. The grid spacing is sufficiently small to ensure that waves of the desired frequency cannot pass through, and are hence reflected back toward the driven element.

Ground: A connection between a device or circuit and the earth or some device serving as the earth.

Half-duplex Transmission (HDX): A channel that allows transmission in only one direction at a time, switching back and forth between transmit and receive. Most spread spectrum wireless LAN equipment is Half-Duplex.

Hand-Off: Typically used to describe the ability of a wireless network to pass the network connection of a roaming device from one connection point to another, without dropping the network connection.

Hierarchical Network: A network architecture in which one node retains control of all traffic across the network medium.

Hertz (Hz): One completed alternating cycle per second. Named after Heinrich R. Hertz, a German physicist. Used as the international unit of frequency. The number of cycles per second.

High-Pass Filter: A signal filter which passes all frequencies above a certain frequency, and attenuates all lower frequencies.

Impedance: Nominal impedance of the device. The variation of this impedance with frequency is measured as VSWR.

In-Line: Power or signal passage through a device which is in series with the line.

Insertion Loss: The loss in signal strength due to the insertion of a device in series with a signal path. Typically measured over the intended operating frequency range of the device.

Intermodulation (Intermod): The distortion product of an amplifier, caused by the interaction of different signal products within the amplifier.

IP: Internet Protocol. The TCP/IP standard protocol that defines the IP as a unit of information passed across an Internet and provides the basis for packet delivery service. The protocol suite is often referred to as TCP/IP because TCP and IP are the two most fundamental protocols.

IP Address: Internet Protocol Address. This is a 32-bit address assigned to host on a TCP/IP Internet. The IP address has a host component and a network component.

Isotropic: A theoretical "isotrope" is a single point in free space which radiates energy equally in every direction.

Jamming: The typically intentional or malicious interference with another radio signal.

Lightning Arrester: A device whose purpose is to eliminate transients on a conductor which are induced by nearby lightning activity.

Linear Amplifier: A device that accurately reproduces a radio wave in magnified form.

Low-Pass Filter: A signal filter which passes all frequencies below a certain frequency, and attenuates all higher frequencies.

Low-Noise Amplifier (LNA): Typically a small-signal amplifier for receive applications.

Maximum Surge: The maximum single surge current and specified wave form that can be handled by the device without failure.

Metal Oxide Varistor (MOV): A type of lightning arrester which offers high resistance to low voltages, and low resistance to high voltages. Placing a MOV from a conductor to ground causes high voltage spikes to short-circuit to ground.

Metropolitan Area Network (MAN): Similar to a LAN but typically over a larger area like a city.

Microwave: Usually referring to all radio frequencies above 2 GHz or so.

Modulate: To vary the amplitude, frequency or phase of a radio frequency wave in accordance with the information to be conveyed.

Multipath Interference: Signal reflections and delayed signal images which are typically associated with indoor wireless LAN applications, and interfere with the desired signal.

Multiple Access: A method for accommodating more users in the same frequency band.

Multipoint: A communications circuit interconnecting several nodes (usually more than two).

Multi-Strike Capability: The ability for a device to survive and work again after a lightning strike.

Narrowband: A signal where the transmission bandwidth is on the order of its information bandwidth.

NDIS: Network Device Interface Specification. The NDIS specification is used for all communication with network adapters. The specification was developed by Microsoft and 3Com to provide a common programming interface for MAC drivers and transport drivers. NDIS works primarily with LAN manager and allows multiple protocol stacks to share a single network interface card.

Network Address: A unique number associated with a host that identifies it to other hosts during network transactions.

NetBIOS: Network basic Input/Output system. It provides a Session Layer interface between network applications running on a PC and the underlying protocol software of the Transport and Network Layers.

Netware: A popular netware operating system developed by Novell.

Network Interface Card (NIC): Usually refers to a network adapter card which installs in a computer.

Noise-Like: Having properties that cause the appearance of random noise.

Omni-Directional Antenna: An antenna which radiates RF energy in a 360 degree pattern about an axis.

Oscillator: A device which produces a "vibration" or variation in level at a given frequency.

Parabolic Dish Antenna: An antenna which utilizes a dish-like reflector to focus radio energy of a specific range of frequencies on a tuned element.

Parabolic Grid Antenna: An antenna which employs an open-frame grid rather than a solid dish reflector. (See also Grid Antenna)

Part 15 Rules (FCC): That part of the FCC regulations which regulates unlicenced use of the ISM bands for wireless networking and other uses.

Patch Antenna: Typically a flat rectangular or round antenna having a hemispherical pattern.

Path Budget: A mathematical model of a wireless communications link which accounts for a wide variety of factors which affect operating range and performance. Sometimes called a "link" budget.

Path Loss: The weakening of a signal over its path of travel due to various factors like terrain, obstructions and environmental conditions.

PCS: Personal Communication System - usually associated with cordless telephone-like devices, and personal data assistant devices. Service is typically digital.

Peer-To-Peer Network: All nodes on the network have equal access to and control of the network medium.

PING: The Packet Internet Groper is a program that is useful for testing and debugging networks. It sends an Echo to the specified host, and waits for a response. It reports success or failure statistics about its operation.

PN: Pseudo Noise - a digital signal with noise-like properties.

Polling: A process in which a device polls the terminals connected to it, asking whether or not they have data to be sent to the host.

Point-to-Point: A communications channel that runs from one point to another.

Point-to-Multipoint: A communications channel that runs from one point to several other points.

Power Meter: A device used to measure radio energy.

Powder Coat: An "environmentally sound" type of durable plastic coating used on various types of outdoor equipment, which is applied electro

Propagation: The travel of a signal through a medium such as air or free space.

Radiation: Electromagnetic energy, such as radio waves, traveling forth into space from a transmitter.

Radio Frequency (RF): Typically a frequency from 20 kHz to 3 GHZ. RF is usually referred to whenever a signal is radiated through the air. Literally, any and all frequencies that can be radiated as an electromagnetic wave.

Radio Wave: A combination of electric and magnetic fields varying at a radio frequency and traveling through space at the speed of light.

Raw Data Rate: Typically refers to the number of bits per second which can be transmitted, not accounting for overhead associated with error correction, packetizing, and other protocol-related factors.

Receive Gain: A measure of receive signal boost contributed by an amplifier or antenna system, and typically measured in dB.

Receiver Sensitivity: The ability of a receiver to differentiate a signal from the background noise.

Remote-Powered: Typically used to describe a device which is powered through the antenna feed cable by way of a "bias-T" or DC injector.

Repeater: Any device which regenerates a signal to continue its propagation, usually increasing total distance or coverage area.

RF Sensing: A circuit which is able to detect the transmitted energy of a transmitter.

Roaming: Typically used to describe a portable communications device moving its network connection from one fixed access point to another.

Router: A router has two or more network interfaces to different networks. The primary function of a router is to direct packets between these networks, delivering them to their final destination or to another router. When used with TCP/IP, the term refers to an IP gateway that routes data using IP destination addresses.

RS-232: A popular connection standard for wired serial data communications.

Safety Ground: The local earth ground. The earth ground which grounds the neutral return A system may be earth grounded as many times as needed.

Saturation: In amplification, a term which describes the point at which the amplifier is producing the most output power it is capable of, basically in an over-driven situation. Typically a device driven to saturation is no longer performing in a linear fashion or distortion-free manner. (See also compression)

Server: A computer or network node that provides services to the network or other nodes.

Short Circuit: An unintended low resistance connection across a low voltage source resulting in high current and possible damage.

Signal-To-Noise Ratio (SNR): A measure of the magnitude of a desired signal relative to the magnitude of an undesired signal or noise.

Spectrum: A series of radiated energies arranged in order of wavelength. The radio spectrum extends from 20 kilohertz upward.

Spectrum Analyzer: An instrument which can be used to view signals across a wide range of frequencies.

Splitter/Combiner: A transmission component which divides or sums power between two or more ports.

Spread Spectrum (SS): A wideband modulation which imparts noise-like characteristics to an RF signal. This communications technique spreads a signal over a wide range of frequencies for transmission and then de-spreads it to the original data bandwidth at the receiver.

Spurious Emissions: Unwanted radio frequency signals emitted from a transmitter that sometimes causes interference.

Throughput: A measure of the volume of data which can be transmitted (typically per second) through a given communications system.

Time Division Multiple Access (TDMA): A digital multiplexing technique whereby each signal is sent and received at a fixed time slots in a series of time slots. The transmitter and receiver must be time-synchronized. Public telephone networks typically use TDMA.

Transceiver: A combination radio transmitter and receiver.

Ultra High Frequency (UHF): Ultra high frequency radio waves that are in the range of 300 to 3,000 MHz.

Very High Frequency (VHF): Very high frequency waves that are in the range of 30 to 300 MHz.

Voltage Standing Wave Ratio (VSWR): The amount of reflected signal due to impedance mis-match.

Wide Area Network (WAN): Large network formed by bridging smaller LANs or using dial-up lines. WANs can span the globe.

Wavelength: The distance that an electromagnetic wave travels in one complete cycle.

Wind Loading: A characteristic of an antenna or other structure which is a measure of the forces applied to the structure due to wind.

Wireless: A new all-encompassing "buzzword" which describes what used to be called "radio", but which typically also implies some of the newer cellular or digital radio technologies as well.

Wireless "Ethernet": A misnomer in actuality since "Ethernet" is a wired system by definition, but appropriate nevertheless to describe CSMA/CA wireless LAN’s&emdash;since their operation has a great deal in common and they are typically integrated easily.

Wireless Local Area Network (WLAN): A short range computer to computer wireless data communications network.

Yagi Antenna: A directional antenna named for one of its inventors, which consists of a boom supporting a series of elements which are typically aluminum rods. Often called a “beam” antenna.

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