Capture Field/Area/Zone (also Interrogation Zone/Area/Volume) The region of the electromagnetic field, determined by the reader/interrogator antenna, in which the transponders are signaled to deliver a response.

Carrier Abbreviated term for Carrier Frequency.

Carrier Frequency The frequency used to carry data by appropriate modulation of the carrier waveform, typically in a radio frequency identification system, by amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), or associated variants.

Case Consists of either an exterior container within a palletized unit load or an individual shipping container.

Channel A medium or medium-associated allocation, such as carrier frequency, for electronic communication.

Channel Encoding The application of coding schemes to facilitate effective channel transmission of the source encoded data.

Channel Decoding The process of operating upon a received transmission to separate the source-encoded data from the channel encoded form.

Character Set A set of characters assembled to satisfy a general or application requirement.

Checksum A summation of check digits used to determine if an error has occurred in the transmission of data.

Chip In data communication terms, the smallest duration of a pseudorandom code sequence used in spread spectrum communication systems.

Chipping The insertion of a RFID tag under the skin of an individual for identification or tracking applications.

Clocking Information Timing signals or pulses used to synchronize the transfer of data from a source to a host destination.

Closed Systems Within the context of radio frequency identification, they are systems in which data handling, including capture, storage, and communication are under the control of the organization to which the system belongs.

Code Plate An alternative colloquial term for transponder or tag.

Collision A term to denote an event in which two or more data communication sources compete for attention at the same time and cause a clash of data, inseparable without some means of anti-collision or contention management.

Collision Avoidance A means of avoiding collisions or clashes of data from different sources competing for attention at the same time.

Compatibility The condition that exists between devices or systems that exhibit equivalent functionality, interface features and performance to allow one to be exchanged for another, without alteration, and achieve the same operational service. An alternative term for Interchangeability.

Concatenation The facility to link together specific items of data, held in data carriers, to form a single file or field of data.

Continuous Reporting A mode of reader/interrogator operation wherein the identification of a transponder is reported or communicated continuously while the transponder remains within the interrogation field.

Continuous Wave Modulation A data modulation scheme in which the data is represented by the carrier signal being switched on and off. The scheme is identical to amplitude shift keying (ASK) with 100% depth of modulation—known as on-off keying (OOK).

Control Characters Characters within a character set which are used to denote a particular control function, such as new line, shift and print control.

Concentrator A means of connecting a number of data communication devices and concentrating packets of data at a local point before onward transmission on a single link to a central data processor or information management system. In contrast to multiplexors concentrators usually have a buffering capability to “queue” inputs that would otherwise exceed transmission capacity.

Contention (Clash) Term denoting simultaneous transponder responses capable of causing potential confusion, and misreading, within a reader/ interrogator system unequipped with anti-contention facilities.

Corruption–Data In data terms, the manifestations of errors within a transmitted data stream due to noise, interference, or distortion.

Data Representations, in the form of numbers and characters for example, to which meaning may be ascribed.

Data Rate In a radio frequency identification system, the rate at which data is communicated between transponder and the reader/interrogator, expressed in baud, bits-1 or bytes-1.

Data Field A defined area of memory assigned to a particular item or items of data.

Data Field Protection The facility to control access to and operations upon items or fields of data stored within the transponder.

Data Identifier A specific character, or string of characters, that denotes the nature or intended use of the data that follows.

Data Transfer The process of transferring data from a data holding source to a destination.

Demodulation Process of recovering channel encoded data from a modulated carrier waveform.

De-tuning The reduction in performance of transponders and readers/interrogators caused by the close proximity of metal influencing the resonance of an electronic tuned circuit.

Dipole (Antenna) A fundamental form of antenna, comprising a single conductor of length approximately equal to half the wavelength of the carrier wave. Provides the basis for a range of other more complex forms of antenna.

Directivity–antenna The ability of an antenna to concentrate radiated energy in a preferred direction, when considered in a transmitter mode. Alternatively, the ability to reject signals that are off-axis to the normal of the antenna, when considered in the receiver mode. May be expressed as a ratio of power radiated per unit solid angle in a defined direction to the total power radiated by the antenna.

Direct Sequence Spread A category of spread spectrum modulation in which the source base-band bit stream is multiplied by a fast pseudo random binary sequence to produce a signal that exhibits broad-band characteristics. Alternatively, the pseudo random sequence and its inverse are used to represent logic 1 and 0.

Dispersion–pulse The spread in duration and form experienced by a pulse in transmission through a communication channel.

Distortion Any disturbance that causes an unwarranted change in the form or intelligibility of a signal. The distortion exhibits a noise-like effect that can be quantified as the ratio of the magnitude of the distortion component to the magnitude of the undistorted signal, usually expressed as a percentage.

Downlink Term which defines the direction of communications as being from reader/interrogator to transponder.

Effective Aperture A term denoting the reception capability of a practical antenna expressed as the product of actual aperture and antenna efficiency.

Efficiency–antenna Two components distinguishable, radiation efficiency and aperture efficiency. Radiation efficiency is expressed as the ratio of total power radiated by the antenna to total power accepted by the antenna from source, for the transmission mode. Aperture efficiency is expressed as the ratio of effective antenna area to the real area of the antenna.

Electromagnetic Coupling A process of transferring modulated data or energy from one system component to another, reader to transponder, for example, by means of an electromagnetic field.

Electromagnetic Field The spatial and temporal manifestation of an electromagnetic source in which magnetic and electric components of intensity can be distinguished and plotted as contours, like contour lines on a map, the planes of the electric and magnetic contours being at right angles to one another. Where the source is varying in time, so too the field components vary with time. Where the source launches an electromagnetic wave, the field may be considered to be propagating.

Electromagnetic Spectrum The range or continuum of electromagnetic radiation, characterized in terms of frequency or wavelength.

Electromagnetic Wave A sinusoidal wave in which electric E and magnetic H components or vectors can be distinguished at right angles to one another, and propagating in a direction that is at right angles to both the E and H vectors. The energy contained within the wave also propagates in the direction at right angles to the E and H vectors. The power delivered in the wave is the vector product of E and H (Pointing Vector).

Electronic Data Interchange Communication of a data message, or messages, automatically between computers or information management systems, usually for the purposes of business transactions.

Electromagnetic Waves Electromagnetic waves are characterized by two field components, a magnetic (H) component and an electric (E) component. These components are mutually perpendicular to each other and to the direction of propagation.

Electronic Data Transfer The transfer of data by electronic communication means from one data handling system to another.

Electronic Label An alternative colloquial term for a transponder.

Encryption of Data A means of securing data, often applied to a plain or clear text, by converting it to a form that is unintelligible in the absence of an appropriate decryption key.

Environmental Parameters, such as temperature, pressure, humidity, and noise, that can have a bearing or impact upon system performance.

EPCglobal EPCglobal is a joint venture between European Article Numbering International (EAN) and the Uniform Code Council (UCC) (GS1) and is leading an effort to create global standards for RFID use.

EPCglobal Inc is an open, worldwide, not-for-profit consortium of supply chain partners working to drive global adoption of the EPC global NetworkTM. Using Electronic Product CodeTM (EPC) and Radio Frequency Identification (RFID) technologies, the EPC global Network will provide for immediate, automatic and accurate identification of any item in the supply chain of any company, in any industry, anywhere in the world. For more information about EPC global, visit http://www.epcglobalinc.org.

EPC Technology Passive RFID technology (readers, tags, etc.) that is built to the most current published EPC global TM Class O and Class 1 specifications and that meets interoperability test requirements as prescribed by EPC global TM.

Error In digital data terms, a result of capture, storage, processing, or communication of data in which a bit or bits assume the wrong values, or bits are missing from a data stream.

Error Burst A group of bits in which two successive erroneous bits are always separated by less than a given number of correct bits.

Error Control Collective Term to accommodate error detection and correction schemes applied to handle errors arising within a data capture or handling system.

Error Detection A term to denote a scheme or action to determine the presence of errors in a data stream.

Error Correction A term to denote a scheme or action for correcting an error detected in a data stream.

Error Correcting Code (ECC) Supplemental bits introduced or source encoded into a data stream to allow automatic correction of erroneous bits and/or derivation of missing bits, in accordance with a specifi c computational algorithm.

Error Correcting Mode Mode defined for a data communication or handling process in which missing or erroneous bits are automatically corrected.

Error Correcting Protocol The rules by which an error correcting mode operates.

Error Management Techniques used to identify and/or correct errors within a data capture and handling system with the objective of assuring the accuracy of data presented to the system user.

ETSI (European Telecommunications Standards Institute) The European standards organization responsible for standardization in telecommunications.

Exciter The electronic circuits used to drive an antenna. The combination of exciter and antenna is often referred to as the transmitter or scanner.

Extended Binary Coded Data Interchange Code (EBCDIC) An eight-bit binary code set, sometimes referred to as extended ASCII, wherein the 128 character set of ASCII are accommodated, together with other characters and control functions, making up a total set of 256 characters.

Exterior Container A MIL-STD-129 defined container, bundle, or assembly that is sufficient by reason of material, design, and construction to protect unit packs and intermediate containers and their contents during shipment and storage. It can be a unit pack or a container with a combination of unit packs or intermediate containers. An exterior container may or may not be used as a shipping container.

Factory Programming The entering of data into a transponder as part of the manufacturing process, resulting in a read-only tag.

False Activation The result of a “foreign” or non-assigned transponder entering the interrogation zone of a radio frequency identification system and effecting a response, erroneous or otherwise.

Far Field The region of an electromagnetic radiation field at a distance from the antenna in which the field distribution is unaffected by the antenna structure and the wave propagates as a plane wave.

Field of View The zone surrounding a reader/interrogator in which the reader/interrogator is capable of communicating with a transponder.

Field Programming Entry of data by an original equipment manufacturer (OEM) or user into a transponder by means of a proprietary programming system, usually undertaken before the device is attached to the item to be identified or accompanied. This facility is usually associated with write once read many (WORM) and read/write (RW) devices. The data entered into a transponder may be by a combination of factory and field programming.

Field Strength The intensity of a field measured in units appropriate to the field concerned. Electric field strengths are measured in volts per meter and magnetic field strengths in amperes per meter.

File A set of data stored within a computer, portable data terminal, or information management system.

Filler Character A redundant character inserted into a data field simply to achieve a desired field length. Also known as a pad character.

Forward Link Communications from reader/interrogator to transponder. Alternatively known as downlink.

Frequency The number of cycles a periodic signal executes in unit time. Usually expressed in hertz (cycles per second) or appropriate weighted units such as kilohertz (kHz), megahertz (MHz), and gigahertz (GHz).

Frequency Hop Rate The frequency at which a frequency hopping spread spectrum (FHSS) system moves between transmission frequencies. It is equal to the reciprocal of the dwell time at an FHSS center frequency.

Frequency Hop Sequence A pseudo random binary sequence (PRBS) determining the hopping frequencies used in frequency hopping spread spectrum (FHSS) systems.

Frequency Hopping Spread Spectrum (FHSS) A category of spread spectrum modulation in which each bit of data is divided into chips and each chip is represented by a different spectral component or tone in the spread spectrum band using a pseudo random sequence to assign tones. Modulated in this way, the transmissions hop from frequency to frequency within the band, requiring a receiver synchronized to the pseudo random chipping sequence to recover the data.

Frequency Modulation (FM) Representation of data or signal states by using different transmission frequencies. Where data is in binary form the modulation constitutes two transmission frequencies and is referred to as frequency shift keying (FSK).

Frequency Shift Keying (FSK) Representation of binary data by switching between two different transmission frequencies.

Full Duplex (FDX) A channel communications protocol that allows a channel to transmit data in both directions at the same time. In RFID, the method of information exchange in which the information is communicated while the transceiver transmits the activation field.

Handshaking A protocol or sequence of signals for controlling the flow of data between devices, which can be hardware implemented or software implemented.

Half Duplex (HDX) A channel communications protocol that allows a channel to transmit data in both directions but not at the same time. In RFID, the method of information exchange in which the information is communicated after the transceiver has stopped transmitting the activation field.

Harmonics Multiples of a principal frequency, invariably exhibiting lower amplitudes. Harmonics can be generated as a result of circuit nonlinearities associated with radio transmissions resulting in harmonic distortion.

Hexadecimal (Hex) A column placing method of representing data to the base of 16, using digits 0–9 and letters A to F for decimal values 10–15. For example, 1010 = A16 and 2210 = 6F16. Used as a convenient short-hand notation for representing 16- and 32-bit memory addresses.

ID Filter A software facility that compares a newly read identification (ID) with those within a database or set, with a view to establishing a match.

Impact Any influence upon a system, environmental or otherwise, that can influence its operational performance.

Incorrect Read The failure to read correctly all or part of the data set intended to be retrieved from a transponder during read or interrogation process. Alternative term for misread.

In-Field Reporting A mode of operation in which a reader/interrogator reports a transponder ID on entering the interrogation zone and then refrains from any further reports until a prescribed interval of time has elapsed.

In-Use Programming The ability to read from and write to a transponder while it is attached to the object or item for which it is being used.

Inductive coupling A process of transferring modulated data or energy from one system component to another, reader to transponder, for example, by means of a varying magnetic field.

Information–general Something that is meaningful. Data may be regarded as information once its meaning is revealed.

Information–theoretic A measure of the scarcity or probability of occurrence of an event, the more scarce the event, the more information conveyed.

Interface A physical or electrical interconnection between communicating devices. See also RS232, RS422, and RS485.

Interference Unwanted electromagnetic signals, where encountered within the environment of a radio frequency identification system, cause disturbance in its normal operation, possibly resulting in bit errors, and degrading system performance.

Interchangeability The condition that exists between devices or systems that exhibit equivalent functionality, interface features, and performance to allow one to be exchanged for another, without alteration, and achieve the same operational service. An alternative term for compatibility.

Interoperability The ability of systems, from different vendors, to execute bi-directional data exchange functions in a manner that allows them to operate effectively together.

Interrogation The process of communicating with and reading a transponder.

Interrogator A fixed or mobile data capture and identification device using a radio-frequency electromagnetic field to stimulate and effect a modulated data response from a transponder or group of transponders present in the interrogation zone. Often used as an alternative term to reader.

Interrogation Zone The region in which a transponder or group of transponders can be effectively read by an associated radio frequency identification reader/interrogator.

Intersymbol Interference Interference arising within a serial bit stream as a result of pulse dispersion and consequential overlapping pulse edges, leading possibly to decoding errors at the receiver.

Isotropic Source An ideal electromagnetic source or radiator exhibiting a perfect spherical energy radiation pattern.

Lifetime The period of time during which an item of equipment exists and functions according to specification. See also Mean Time Between Failures and Mean Time to Repair.

Manchester Coding A bi-phase code format in which each bit in the source encoded form is represented by two bits in the derived or channel encoded form. The transformation rule ascribes 01 to represent 0 and 10 to represent 1.

Manufacturers Tag ID (MfrTagID) A reference number that uniquely identifies the tag.

Mean Time Between Failures The average or mean time interval between failures, often expressed as the reciprocal of the constant failure rate.

Mean Time to Repair The length of time that a system is non-operational between failure and repair.

Memory A means of storing data in electronic form. A variety of random access (RAM), read-only (ROM), write once–read many (WORM), and read/write (RW) memory devices can be distinguished.

Memory Modules Colloquial term for a read/write or re-programmable transponder.

Misread A condition that exists when the data retrieved by the reader/interrogator is different from the corresponding data within the transponder. Alternative term for incorrect read.

Modulation A term to denote the process of superimposing (modulating) channel encoded data or signals onto a radio frequency carrier to enable the data to be effectively coupled or propagated across an air interface. Also used as an associative term for methods used to modulate carrier waves. Methods generally rely on the variation of key parameter values of amplitude, frequency, or phase. Digital modulation methods principally feature amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), or variants. See also Amplitude, Frequency and Phase Modulation, Amplitude Shift Keying, Frequency Shift Keying, and Phase Shift Keying.

Modulation Index The size of variation of the modulation parameter (amplitude, frequency, or phase) exhibited in the modulation waveform.

Multiple Reading The process or capability of a radio frequency identification reader/interrogator to read a number of transponders present within the system’s interrogation zone at the same time.

Multiplexor (Multiplexer) A device for connecting a number of data communication channels and combining the separate channel signals into one composite stream for onward transmission through a single link to a central data processor or information management system. At its destination the multiplexed stream is de-multiplexed to separate the constituent signals. Multiplexors are similar to concentrators in many respects, a distinction being that concentrators usually have a buffering capability to “queue” inputs that would otherwise exceed transmission capacity.

Noise Unwanted extraneous electromagnetic signals encountered within the environment, usually exhibiting random or wide band characteristics, and viewed as a possible source of errors through influence upon system performance.

Noise Immunity A measure of the extent or capability of a system to operate effectively in the presence of noise.

Omnidirectional A description of a transponder’s ability to be read in any orientation.

On-Off Keying (OOK) A special case of amplitude shift keying (ASK) in which the carrier is switched between full carrier amplitude and zero or absence of carrier amplitude, according to data value (1 or 0).

Open Systems Within the context of radio frequency identification, they are systems in which data handling, including capture, storage, and communication, is determined by agreed standards, so allowing various and different users to operate without reference to a central control facility.

Orientation The attitude of a transponder with respect to the antenna, expressed in three-dimensional angular terms, with range of variation expressed in terms of skew, pitch, and roll.

Orientation Sensitivity The sensitivity of response for a transponder expressed as a function of angular variation or orientation.

Out of Field Reporting A mode of operation in which the identification of a transponder is reported as or once the transponder leaves the reader interrogation zone.

Pallet (palletized unit load) A MIL-STD-129 defined quantity of items, packed or unpacked, arranged on a pallet in a specified manner and secured, strapped, or fastened on the pallet so that the whole palletized load is handled as a single unit. A palletized or skidded load is not considered to be a shipping container.

Parity A simple error detecting technique, used to detect data transmission errors, in which an extra bit (0 or 1) is added to each binary represented character to achieve an even number of 1 bits (even parity) or an odd number of 1 bits (odd parity). By checking the parity of the characters received a single errors can be detected. The same principle can be applied to blocks of binary data.

Passive Transponder (Tag) A battery-free data carrying device that reacts to a specific, reader-produced, inductively coupled or radiated electromagnetic field, by delivering a data modulated radio frequency response. Having no internal power source, passive transponders derive the power they require to respond from the reader/interrogator’s electromagnetic field.

Penetration Term used to indicate the ability of electromagnetic waves to propagate into or through materials. Non-conducting materials are essentially transparent to electromagnetic waves, but absorption mechanisms, particularly at higher frequencies, reduce the amount of energy propagating through the material. Metals constitute good reflectors for freely propagating electromagnetic waves, with very little of an incident wave being able to propagate into the metal surface.

Phase Modulation (PM) Representation of data or signal states by the phase of a fixed frequency sinusoidal carrier wave. Where data is in binary, form the modulation involves a phase difference of 180° between the binary states and is referred to as Phase Shift Keying (PSK).

Phase Shift Keying (PSK) Representation of binary data states, 0 and 1, by the phase of a fi xed frequency sinusoidal carrier wave, a difference of 180° being used to represent the respective values.

Polar Field Diagram A graphical representation of the electric or magnetic field intensity components of an electromagnetic field, expressed on a polar co-ordinate system. Typically used to illustrate the field characteristics of an antenna.

Polarization The locus or path described by the electric field vector of an electromagnetic wave, with respect to time.

Polarization Summary Polarization is a term that often arises in the literature and when considering radio frequency communication and RFID. The polarization of a propagating wave is determined by the locus or path described by the electric field vector with respect to time. If we ascribe an x, y, z co-ordinate system to a propagating wave as illustrated below, with the direction of propagation being in the z direction, the electric field vector, E, will be in the x, y plane. If E remains in the same orientation with respect to time, so that its locus describes a straight line, the wave is said to be linearly polarized. However, if the locus describes a circular motion with respect to time the wave is said to be circularly polarized. Where the locus describes an elliptical path the wave is said to be elliptically polarized.

Circular polarization is often used in communication systems since the orientation of the transmitting and receiving antenna is less important than it is with linearly polarized waves. The magnetic vector, H, always remains perpendicular to the E vector. Using an IEEE convention, a clockwise circular rotating wavefront approaching a receiver is defined as being left-hand circular (LHC) polarized.

Port Concentrator A device that accepts the outputs from a number of data communication interfaces for onward transmission into a communications network.

Power Levels and Flux Density The vector product of electric and magnetic field strengths within an electromagnetic wave, expressed as levels in watts and as a power flux density, measured at a distance from the source, in watts per square meter. Low power radio frequency transmissions are generally expressed in milli- or microwatts.

Programmability The ability to enter data and to change data stored in a transponder.

Programmer An electronic device for entering or changing (programming) data in a transponder, usually via a close proximity, inductively coupled data transfer link.

Programming The act of entering or changing data stored in a transponder.

Projected Lifetime The estimated lifetime for a transponder often expressed in terms of read and/or write cycles or, for active transponders, years, based upon battery life expectancy and, as appropriate, read/write activity.

Protocol A set of rules governing a particular function, such as the flow of data/information in a communication system.

Proximity Term often used to indicate closeness of one system component with respect to another, such as that of a transponder with respect to a reader.

Proximity Sensor An electronic device that detects and signals the presence of a selected object. When used in association with a radio frequency identification system, the sensor is set up to sense the presence of a tagged or transponder carrying object when it enters the vicinity of the reader/interrogator so that the reader can then be activated to effect a read.

Pulse Dispersion The spread in width or duration of a pulse during transmission through a practical transmission system, due to the influence of distributed reactive components

Radio Frequency Identification An automatic identification and data capture system comprising one or more reader/interrogators and one or more transponders in which data transfer is achieved by means of suitably modulated inductive or radiating electromagnetic carriers.

Radio Frequency Tag Alternative term for a transponder.

Range–Read The maximum distance between the antenna of a reader/ interrogator and a transponder over which the read function can be effectively performed. The distance will be influenced by orientation and angle with respect to the antenna, and possibly by environmental conditions.

Range–Programming The maximum distance between the antenna of a reader/interrogator and a transponder over which a programming function can be effectively performed. Usually shorter than the read range, but may be influenced by orientation and angle with respect to the antenna, and possibly by environmental conditions.

Read The process of retrieving data from a transponder and, as appropriate, the contention and error control management, and channel and source decoding required to recover and communicate the data entered at source.

Readability The ability to retrieve data under specified conditions.

Reader/Interrogator An electronic device for performing the process of retrieving data from a transponder and, as appropriate, the contention and error control management, and channel and source decoding required to recover and communicate the data entered at source.

Reader/Writer The device may also interface with an integral display and/or provide a parallel or serial communications interface to a host computer or industrial controller.

Read Only Term applied to a transponder in which the data is stored in an unchangeable manner and can therefore only be read.

Read Rate The maximum rate at which data can be communicated between transponder and reader/interrogator, usually expressed in bits per second.

Read/Write Applied to a radio frequency identification system, it is the ability both read data from a transponder and to change data (write process) using a suitable programming device.

Redundancy In information terms, it describes the additional bits, such as those for error control or repeated data, over and above those required for transmitting the information message.

Re-programmability The ability to change the data content of a transponder using a suitable programming device.

RF Tag Alternative, short-hand term for a transponder.

RS232 A common physical interface standard specified by the EIA for the interconnection of devices. The standard allows for a single device to be connected (point-to-point) at baud values up to 9,600 bps, at distances up to 15 meters. More recent implementations of the standard may allow higher baud values and greater distances.

RS422 A balanced interface standard similar to RS232, but using differential voltages across twisted pair cables. Exhibits greater noise immunity than RS232 and can be used to connect single or multiple devices to a master unit, at distances up to 3,000 meters.

RS485 An enhanced version of RS422, which permits multiple devices (typically 32) to be attached to a two wire bus at distances of over one kilometer.

SAW (Surface Acoustic Wave) Devices Devices using a transponder technology in which low power microwave signals are converted to ultrasonic waves by and on the surface of a piezoelectric crystal material forming the tag. Surface applied “finger” transducers determine the form and data content of the reflected return signal.

Scrambling The rearrangement or transposition of data to enhance security of stored data or the effectiveness of error control schemes.

Scanner The combination of antenna, transmitter (or exciter), and receiver into a single unit is often referred to as a scanner. With the addition of electronics to perform the necessary decoding and management functions to deliver the source data, the unit becomes a reader.

Screening The process of avoiding or minimizing electromagnetic interference by use of electromagnetic reflective and absorptive materials, suitably structured or positioned to reduce interaction between the source of potential interference and the circuit being protected.

Sensor An electronic device that senses a physical entity and delivers an electronic signal that can be used for control purposes.

Separation A term used to denote the operational distance between two transponders.

Shipping Contain A MIL-STD-129 defined exterior container which meets carrier regulations and is of sufficient strength, by reason of material, design, and construction, to be shipped safely without further packing (e.g., wooden boxes or crates, fiber and metal drums, and corrugated and solid fi berboard boxes).

Signal to Noise (S/N) The ratio of signal level to the level of noise present in a system, usually expressed in decibels.

Signal to Noise & Distortion The ratio of combined signal, noise, and distortion levels to the combined level of noise and distortion present in a system.

Sinusoidal Carrier A fundamental waveform, characterized by a single frequency and wavelength, used to carry data or information by modulating some feature of the waveform.

Source Decoding The process of recovering the original or source data from a received source encoded bit stream.

Source Encoding The process of operating upon original or source data to produce an encoded message for transmission.

Spectrum–Electromagnetic The continuum of electromagnetic waves, distinguished by frequency components and bands that exhibit particular features or have been used for particular applications, including radio, microwave, ultraviolet, visual, infrared, X-rays and gamma rays.

Spectrum–Signal Expression used to denote the make-up of a signal or waveform in terms of sinusoidal components of different frequency and phase relationship (spectral components).

Spectrum Mask The maximum power density of a transmission expressed as a function of frequency.

Spurious Emissions Usually denotes unwanted electromagnetic harmonics. Type approval testing includes measurement of harmonic emissions arising from the reader, to ensure they are within specified limits.

Spread Spectrum Techniques for uniformly distributing or spreading the information content of a data carrying signal over a frequency range considerably larger than required for narrow band communication, allowing data to be recoverable under conditions of strong interference and noise.

SRD (Short Range Device) A tag that is used at short range (less than 100 mm).

Synchronization The process of controlling the transmission of data using a separate or derived clocking signal.

Synchronous Transmission A method of data transmission that requires timing or clocking information in addition to data.

Tag Colloquial term for a transponder. Commonly used and the term preferred by AIM for general usage.

Tolerance The maximum permissible deviation of a system parameter value, caused by any system or environmental influence or impact. Usually expressed in parts per million (ppm). Tolerances are specified for a number of radio frequency parameters, including carrier frequencies, sub-carriers, bit clocks, and symbol clocks.

Transceiver A transmitter/receiver device used to both receive and transmit data.

Transmitter (Exciter) An electronic device for launching an electromagnetic wave or delivering an electromagnetic field for the purpose of transmitting or communicating energy or modulated data/information. Often considered separately from the antenna, as the means whereby the antenna is energized. In this respect it is also referred to as an exciter.

Transponder An electronic transmitter/responder, commonly referred to as a tag.

Unit Pack A MIL-STD-129 defined unit pack, specifically, the first tie, wrap, or container applied to a single item, or to a group of items, of a single stock number, preserved or unpreserved, which constitutes a complete or identifi able package.

Unitized Active Tag An active tag or transponder in which the batteries are replaceable or sealed within the device.

Uplink Term that defines the direction of communications as being from transponder to reader/interrogator.

Vector A quantitative component that exhibits magnitude, direction, and sense.

Verification The process of assuring that an intended operation has been performed.

Write The process of transferring data to a transponder, the internal actions of storing the data, which may also encompass the reading of data to verify the data content.

Write Rate The rate at which data is transferred to a transponder and stored within the memory of the device and verified. The rate is usually expressed as the average number of bits or bytes per second over which the complete transfer is performed.