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GLOSSARY OF RFID TERMS
  If there is a term that should be in this glossary but isn't, please let us know by sending e-mail to editor@rfidjournal.com.
 
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Glossary Results   M - S
 M
Manufacturing Execution System: A system with which companies can measure and control critical production activities, offering improved traceability, productivity and quality. MES solutions serve numerous functions, such as equipment tracking, product genealogy, labor tracking, inventory management, costing, electronic signature capture, and defect and resolution monitoring,
Memory: The amount of data that can be stored on the microchip in an RFID tag. It can range from 64 bits to 2 kilobytes or more on passive tags.
Memory block: Memory on the microchip in an RFID tag is usually divided into sections, which can be read or written to individually. Some blocks might be locked, so data can't be overwritten, while others are not.
MEMS: Micro-electro-mechanical systems, smaller than microscopic dust mites and used in a variety of applications, from inkjet printers to accelerometers that deploy air bags in cars. A MEMS RFID tag contains micromechanical components that are expected to be rugged and easier to produce, and that can be attached directly to medical devices. Such a tag can withstand exposure to wide temperature ranges and gamma radiation.
Micro-electro-mechanical Systems: Also known as MEMS, smaller than microscopic dust mites and used in a variety of applications, from inkjet printers to accelerometers that deploy air bags in cars. A MEMS RFID tag contains micromechanical components that are expected to be rugged and easier to produce, and that can be attached directly to medical devices. Such a tag can withstand exposure to wide temperature ranges and gamma radiation.
Microcontroller: A complete microprocessor on a chip. A microcontroller includes a central processing unit, RAM or EPROM, clock and control circuits, and serial and parallel I/0 ports.
Microprocessor: The silicon chip that is the heart of a computing system. It includes a central processing unit, internal registers, control logic and bus interfaces to external memory and input-output ports. Some advanced systems also include floating point processors and some memory.
Microwave: A high-frequency electromagnetic wave, one millimeter to one meter in wavelength.
Microwave tags: A term that is sometimes used to refer to RFID tags that operate at 5.8 GHz. They have very high transfer rates and can be read from as far as 30 feet away, but they use a lot of power and are expensive. (Some people refer to any tag that operates above about 415 MHz as a microwave tag.)
Middleware: In the RFID world, this term is generally used to refer to software that resides on a server between readers and enterprise applications. The middleware is used to filter data and pass on only useful information to enterprise applications. Some middleware can also be used to manage readers on a network.
Milliwatt: A unit of power equal to one thousandth of a watt.
MIPS: Million instructions per second
Mobile Reader: An RFID interrogator that can be carried or transported on a person, vehicle or apparatus, enabling employees to read the unique ID numbers of RFID tags attached to items in a warehouse or other setting along the supply chain.
Modulation: Changing the radio waves traveling between the reader and the transponder in ways that enable the transmission of information. Waves can be changed in a variety of ways that can be picked up by the reader and turned into the ones and zeroes of binary code. Waves can be made higher or lower (amplitude modulation) or shifted forward (phase modulation). The frequency can be varied (frequency modulation), or data can be contained in the duration of pulses (pulse-width modulation).

Monostatic: A monostatic RFID interrogator, or reader, uses the same antenna to transmit RF energy to and receive RF energy from the RFID tag.
Multimode: Transponders are called "multimode" when they can be programmed to operate according to several different standards.
Multiple access schemes: Methods of increasing the amount of data that can be transmitted wirelessly within the same frequency spectrum. Some RFID readers use Time Division Multiple Access, or TDMA, meaning they read tags at different times to avoid interfering with one another.
Multiplexer: An electronic device that allows a reader to have more than one antenna. Each antenna scans the field in a preset order. This reduces the number of readers needed to cover a given area, such as a dock door, and prevents the antennas from interfering with one another.
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 N
NanoBlock: The term Alien Technology uses to describe its tiny microchips, which are about the width of three human hairs.
National Institute for Standards and Technology: An American standards body that establishes standards for information-processing technology, particularly IT used by the Federal government.

Near-field communication: RFID reader antennas emit electromagnetic radiation (radio waves). If an RFID tag is within full wavelength of the reader, it is sometimes said to be in the "near field" (as with many RFID terms, definitions are not precise). If it is more than the distance of one full wavelength away, it is said to be in the "far field." The near field signal decays as the cube of distance from the antenna, while the far field signal decays as the square of the distance from the antenna. So passive RFID systems that rely on near-field communication (typically low- and high-frequency systems) have a shorter read range than those that use far field communication (UHF and microwave systems)
NFC: See near-field communication
Noise: Unwanted ambient electrical signals or electromagnetic energy found in the operating environment of RFID equipment. Other RF devices, robots, electric motors and other machines can cause noise.
Nominal range: The read range at which the tag can be read reliably.
Non-volatile memory: A generic term for the memory that holds its contents after power has been removed. EPROM, EEPROM and FLASH are examples of non-volatile memory.
Null spot: Area in the reader field that doesn't receive radio waves. This is essentially the reader's blind spot. It is a phenomenon common to UHF systems.
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 O
Object Name Service: An Auto-ID Center-designed system for looking up unique Electronic Product Codes and pointing computers to information about the item associated with the code. ONS is similar to the Domain Name Service, which points computers to sites on the Internet.
OEM: See original equipment manufacturer
One-time programmable: Memory that can be written to, or programmed, only once and is afterwards write protected. After the memory is written to, it is like read-only memory.
One-time programmable tag: Also called a field-programmable tag. An RFID tag that can be written to once and read many times (see WORM).
ONS: See Object Name Service

Optical Character Recognition: A type of computer software designed to translate images of handwritten or typewritten text (usually captured by a scanner) into machine-editable text, or to translate pictures of characters into a standard encoding scheme (such as ASCII or Unicode). OCR began as a field of research in pattern recognition, artificial intelligence and machine vision.

Order Management System: A software system used in a number of industries for order entry and processing. Such industries include e-commerce, cataloging and financial securities.
Orientation: The position of a tag antenna vis-à-vis a reader antenna. With UHF systems, readers can be either circular-polarized or linear-polarized. When using a linear polarized antenna, the tag reader and antenna reader must be in alignment in order to achieve the longest reading distance. If that tag antenna is aligned vertically and the reader is sending out signals horizontally, only a small portion of the energy emitted by the reader will hit the tag antenna.
Original equipment manufacturer: A company that builds its own products from components bought from other manufacturers.

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 P
Passive tag: An RFID tag without its own power source and transmitter. When radio waves from the reader reach the chip’s antenna, the energy is converted by the antenna into electricity that can power up the microchip in the tag. The tag is able to send back information stored on the chip. Today, simple passive tags cost from U.S. 20 cents to several dollars, depending on the amount of memory on the tag, packaging and other features.
Patch antenna: A term used to describe a square reader antenna made from a solid piece of metal or foil.
Penetration: The ability of a particular radio frequency to pass through non-metallic materials.
Personal Identity Verification Format: A format for improving the identification and authentication of federal employees and contractors for access to federal facilities and information systems.
Phantom read: When a reader reports the presence of a tag that doesn't exist. This phenomenon is also sometimes called a phantom transaction or false read.
Phase: A part of a complete cycle of a waveform as measured from a specified reference point.
Phase Jitter Modulation: A variant of phase-shift keying, created by Magellan Technology, which operates at 13.56 MHz and complies with the ISO/IEC 18000 3 Mode 2 standard. PJM technology enables a write data rate of up to 424 kilobits per second and a read data rate of 106 kbit/s. It is particularly suited to item-level tagging in the pharmaceutical industry.
Phase shift keying: A method of communicating data by shifting the waveform's period. Instead of being at the zero axis at a specific point in time, the wave might be shifted forward so that it is at its peak. The reader's digital signal processor might interpret the out of phase signal as a one or zero.
Physical Markup Language: An Auto-ID Center-designed method of describing products in a way computers can understand. PML is based on the widely accepted eXtensible Markup Language used to share data over the Internet in a format all computers can use. The idea is to create a computer language that companies can use to describe products so that computer can search for, say, all "soft drinks" in inventory.
PML: See Physical Markup Language

PML Server: A server that responds to requests for Physical Markup Language (PML) files related to individual Electronic Product Codes. The manufacturer of the item will maintain the PML files and servers. The name PML server has been replaced by EPC Information Service.
Portal: An RFID interrogator gateway used in manufacturing settings. Forklifts or other methods are used to transport tagged items through a portal reader to collect RFID tag data.
Power level: The amount of RF energy radiated from a reader. The higher the power output, the longer the read range, but most governments regulate power levels to avoid interference with other devices.
Printer: An RFID printer, or printer/encoder, is a device that prints a label with an embedded RFID transponder and encodes information in the chip within the transponder.
Printer/encoder: See printer
Private key: A cryptographic key known only to the owner.
Programming a tag: Writing data to an RFID tag. When a serial number is first written to a tag, this is sometimes called "commissioning a tag."
Protocol: A set of rules that govern communications systems. (See Air-interface protocol.)
Proximity sensor: A device that detects the presence of an object and signals another device. Proximity sensors are often used on manufacturing lines to alert robots or routing devices on a conveyor to the presence of an object. They can be used in RFID systems to turn on readers.
Public key: The publicly available and distributed key used in public key cryptography systems.

Public key cryptography: A generic term for all public key algorithms. PKC uses a pair of numeric "keys," one public and one private key. The public key is published and can be used by anyone to either encrypt a message for the owner of the corresponding private key or to verify a signature generated by the owner of the secret key.
Public key infrastructure: A system of storing and distributing public keys together with their current status.
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 Q
Quiet tag: An RFID tag that can be read only occasionally with the interrogator output at full power, or which can only be read at very close range.

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 R
Radio Frequency Identification: A method of identifying unique items using radio waves. Typically, a reader communicates with a tag, which holds digital information in a microchip. But there are chipless forms of RFID tags that use material to reflect back a portion of the radio waves beamed at them.
RAM: See random access memory
Random access memory: Memory used for temporary storage of data. Information stored in RAM is lost when power is removed.
Read: The process of retrieving data stored on an RFID tag by sending radio waves to the tag and converting the waves the tag sends back into data.
Read field: See reader field.
Read range: The distance from which a reader can communicate with a tag. Active tags have a longer read range than passive tags because they use their own power source (usually a battery) to transmit signals to the reader. With passive tags, the read range is influenced by frequency, reader output power, antenna design, and method of powering up the tag. Low-frequency tags use inductive coupling, which requires the tag to be within a few feet of the reader.
Read rate: A term usually used to describe the number of tags that can be read within a given period or the number of times a single tag can be read within a given period. The read rate can also mean the maximum rate at which data can be read from a tag expressed in bits or bytes per second. (See Data transfer rate.)
Read-only: A term used to describe RFID tags that contain data that cannot be changed unless the microchip is reprogrammed electronically.
Read-write: A term used to describe an RFID tag that can store new information on its microchip. These tags are often used on reusable containers and other assets. When the contents of the container are changed, new information is written to the tag.

Reader: A device used to communicate with RFID tags. The reader has one or more antennas, which emit radio waves and receive signals back from the tag. The reader is also sometimes called an interrogator because it "interrogates" the tag.

Reader field: The area of coverage. Tags outside the reader field do not receive radio waves and can't be read. This is also sometimes referred to as the read field.
Reader module: The electronics of a reader, including a digital signal processor, on a circuit board. Modules can be put in an RFID label printer or other device, as opposed to a standalone reader.
Reader talks first: A means by which a passive UHF reader communicates with tags in its read field. The reader sends energy to the tags but the tags sit idle until the reader requests them to respond. The reader is able to find tags with specific serial numbers by asking all tags with a serial number that starts with either 1 or 0 to respond. If more than one responds, the reader might ask for all tags with a serial number that starts with 01 to respond, and then 010. This is called "walking" a binary tree, or "tree walking." (See singulation.)
Real-time locating system: A system of finding the position of assets, using active RFID tags. The tags broadcast a signal, which is received by three reader antennas. The time each signal is received is passed on to a software system that uses triangulation to calculate the location of the asset. RTLS is used to find containers in a distribution yard, and many automakers use it to track parts bins within a large factory.

Return on Investment: The ratio of money gained or lost on an investment relative to the amount invested. The amount gained or lost may be referred to as interest, profit/loss, gain/loss or net income/loss, while the money invested may be referred to as the asset, capital, principal or cost basis of the investment. ROI is sometimes also known as "rate of profit" or "rate of return."
Reverse channel: The path through which energy travels from the RFID tag to the interrogator, or reader. It is also sometimes called the back channel.
RFID: See radio frequency identification

RFID Journal: The leading independent publication focused on radio frequency identification and its many business applications.
RFID tag: A microchip attached to an antenna that is packaged in a way that it can be applied to an object. The tag picks up signals from and sends signals to a reader. The tag contains a unique serial number, but may have other information, such as a customers' account number. Tags come in many forms, such smart labels that can have a barcode printed on it, or the tag can simply be mounted inside a carton or embedded in plastic. RFID tags can be active, passive or semi-passive.
RTLS: See real-time locating system
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 S
Savants: A term used to describe distributed middleware designed by the Auto-ID Center to filter data from EPC readers and pass it on to enterprise systems. It was envisioned that Savants would reside on servers across the EPC Network and pass data to one another and act as a kind of nervous system for the network. The term is being phase out by EPCglobal and many of the functions of Savants are being incorporated in commercial middleware products.

SAW: A technology used for automatic identification in which low power microwave radio frequency signals are converted to ultrasonic acoustic signals by a piezoelectric crystalline material in the transponder. Variations in the reflected signal can be used to provide a unique identity.
Scanner: An electronic device that can send and receive radio waves. When combined with a digital signal processor that turns the waves into bits of information, the scanner is called a reader or interrogator.
Seismic Sensor: A device combining a supersensitive piezoelectric accelerometer with an ultra-low-noise amplifier, used in such applications as earthquake detection, geophysics, geothermal development, structural analysis and mine safety.
Semi-passive tag: Similar to active tags, but the battery is used to run the microchip's circuitry but not to broadcast a signal to the reader. Some semi-passive tags sleep until they are woken up by a signal from the reader, which conserves battery life. Semi-passive tags can cost a dollar or more. These tags are sometimes called battery-assisted tags.
Sensor: A