source: RFID Journal

RFID; curse or blessing?
Radio frequency identification is a generic term for technologies that use radio waves to automatically identify individual items. RFID will provide more, and more accurate information on e.g. product ingredients origin, marketing effects or the adequacy of your logistics. This will effect your information systems as well e.g. storage capacity required or attuning of your ERP architecture.
TruePS provides services (SAPiens, ERP, NewNetion) making opportunities add to your competitive strength.
Radio frequency identification is a generic term for technologies that use radio waves to automatically identify individual items. RFID will provide more, and more accurate information on e.g. product ingredients origin, marketing effects or the adequacy of your logistics. This will effect your information systems as well e.g. storage capacity required or attuning of your ERP architecture.
TruePS provides services (SAPiens, ERP, NewNetion) making opportunities add to your competitive strength.

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Faith in the System

There are still many problems to be solved before RFID technology can dramatically improve efficiency throughout the global supply chain. But our democratic capitalist system means they will be resolved quickly. By Mark Roberti - RFID Journal

June 21, 2004— Before RFID technology can deliver on its promise to dramatically improve efficiency across the supply chain, many issues need to be addressed. Tag costs need to come down dramatically. New software needs to be developed
to take advantage of RFID data. Standards need to be agreed upon. These issues are so significant that that some CEOs wonder if RFID will ever live up to its promise. It will, and here's why.

As long as there is a need for something, capitalism will reward those companies that overcome problems, deliver value and fulfill the need. There was a market for low-cost RFID tags and all the associated infrastructure needed to take advantage of those tags, and big companies, including Unilever, Gillette, Metro, Procter & Gamble, Tesco and Wal-Mart, backed the Auto-ID Center to create such technology.

Once Wal-Mart announced that it would require RFID tags carrying Electronic Product Codes to be put on pallets and cases beginning January 2005, the demand for low-cost tags and related technologies became obvious and the capitalist system responded. Big and small companies moved into the market to provide the hardware, software and services needed to begin taking advantage of the technology.

Some CEOs are not looking at how much progress has been made over the past year; they're looking at how much progress still needs to be made. But there is good reason to believe that the remaining obstacles will be overcome. The pace of innovation in the RFID industry is speeding up. Each week, RFID Journal reports on new companies bringing new expertise to the market to solve problems and get a piece of this new market.

Given the immature state of RFID technology today, CEOs have two choices. They can sit back and wait and see whether the technology evolves to the point where it delivers the promised benefits. Or they can have faith that the capitalist system will draw talent, expertise and financial resources to solve problems and innovate in ways that enable RFID to live up to expectations. Given the enormous progress that I've seen over the past two years, the right course seems obvious.

Mark Roberti is the founder and editor of RFID Journal.

 

RFID security !?

 

The German technology consultant Lukas Grunwald of DN-Systems Enterprise Solutions revealed at the Black Hat Security Briefings that RFID tags can be read and written using a simple handheld device and a piece of software he wrote, called RFDump, freely available on the Web . It can be used in a legal way (e.g. for privacy reasons, to delete information when you leave a shop) but also for shoplifting (by changing the identity of the purchased goods)...

More at News.com : RFID tags become hacker target.

 

FAQ's

 

What Is Automatic Identification?
Automatic identification, or auto ID for short, is the broad term given to a host of technologies that are used to help machines identify objects. Auto identification is often coupled with automatic data capture. That is, companies want to identify items, capture information about them and somehow get the data into a computer without having employees type it in. The aim of most auto-ID systems is to increase efficiency, reduce data entry errors, and free up staff to perform more value-added functions. There are a host of technologies that fall under the auto-ID umbrella. These include bar codes, smart cards, voice recognition, some biometric technologies (retinal scans, for instance), optical character recognition, radio frequency identification (RFID) and others. Back to Top

What is RFID?
Radio frequency identification, or RFID, is a generic term for technologies that use radio waves to automatically identify individual items. There are several methods of identifying objects using RFID, but the most common is to store a serial number that identifies a product, and perhaps other information, on a microchip that is attached to an antenna (the chip and the antenna together are called an RFID transponder or an RFID tag). The antenna enables the chip to transmit the identification information to a reader. The reader converts the radio waves returned from the RFID tag into a form that can then be passed on to computers that can make use of it. Back to Top

How does an RFID system work?
The system consists of a tag, which is made up of a microchip with a coiled antenna, and an interrogator or reader with an antenna. The reader sends out electromagnetic waves that form a magnetic field when they "couple" with the antenna on the RFID tag. A passive RFID tag draws power from this magnetic field and uses it to power the microchip's circuits. The chip then modulates the waves that the tag sends back to the reader and the reader converts the new waves into digital data. Back to Top

Is there any health risks associated with RFID and radio waves?
RFID uses the low-end of the electromagnetic spectrum. The waves coming from readers are no more dangerous than the waves coming to your car radio. Back to Top

Why is RFID better than using bar codes?
RFID is not necessarily "better" than bar codes. The two are different technologies and have different applications, which sometimes overlap. The big difference between the two is bar codes are line-of-sight technology. That is, a scanner has to "see" the bar code to read it, which means people usually have to orient the bar code towards a scanner for it to be read. Radio frequency identification, by contrast, doesn't require line of sight. RFID tags can be read as long as they are within range of a reader. Bar codes have other shortcomings as well. If a label is ripped, soiled or falls off, there is no way to scan the item. And standard bar codes identify only the manufacturer and product, not the unique item. The bar code on one milk carton is the same as every other, making it impossible to identify which one might pass its expiration date first. Back to Top

Will RFID replace bar codes?
Probably not. Bar codes are inexpensive and effective for certain tasks. It is likely that RFID and bar codes will coexist for many years. Back to Top

Is RFID new?
RFID is a proven technology that's been around since the Second World War. Up to now, it's been too expensive and too limited to be practical for many commercial applications. But if tags can be made cheaply enough, they can solve many of the problems associated with bar codes. Radio waves travel through most non-metallic materials, so they can be embedded in packaging or encased in protective plastic for weather-proofing and greater durability. And tags have microchips that can store a unique serial number for every product manufactured around the world. Back to Top

If RFID has been around so long and is so great, why aren't all companies using it?
Many companies have invested in RFID systems to get the advantages they offer. These investments are usually made in closed-loop systems – that is, when a company is tracking goods that never leave its own control. That's because all existing RFID systems use proprietary technology, which means that if company A puts an RFID tag on a product, it can't be read by Company B unless they both use the same RFID system from the same vendor. But most companies don't have closed-loop systems, and many of the benefits of tracking items come from tracking them as they move from one company to another and even one country to another. Back to Top

Is the lack of standards the only thing that has prevented RFID from being more widely used?
Another problem is cost. RFID readers typically cost $1,000 or more. Companies would need thousands of readers to cover all their factories, warehouses and stores. RFID tags are also fairly expensive – 50 cents or more – which makes them impractical for identifying millions of items that cost only a few dollars (see below). Back to Top

How much do RFID tags costs?
They can cost as little as 30 cents or as much as $50 depending on the type of tag and the application. Generally speaking, finished smart labels that can be applied top products typically cost 50 cents or more. Active tags – those with a battery – can cost far more. And if you bundle in a sophisticated sensor, the cost can rise to more than $100. Back to Top

What is the difference between low-, high-, and ultra-high frequencies?
Just as your radio tunes in to different frequency to hear different channels, RFID tags and readers have to be tuned to the same frequency to communicate. RFID systems use many different frequencies, but generally the most common are low- (around 125 KHz), high- (13.56 MHz) and ultra-high frequency, or UHF (850-900 MHz). Microwave (2.45 GHz) is also used in some applications. Radio waves behave differently at different frequency, so you have to choose the right frequency for the right application. Back to Top

How do I know which frequency is right for my application?
Different frequencies have different characteristics that make them more useful for different applications. For instance, low-frequency tags are cheaper than ultra high frequency (UHF) tags, use less power and are better able to penetrate non-metallic substances. They are ideal for scanning objects with high-water content, such as fruit, at close range. UHF frequencies typically offer better range and can transfer data faster. But they use more power and are less likely to pass through materials. And because they tend to be more "directed," they require a clear path between the tag and reader. UHF tags might be better for scanning boxes of goods as they pass through a bay door into a warehouse. It is probably best to work with a consultant, integrator or vendor that can help you choose the right frequency for your application. Back to Top

Do all countries use the same frequencies?
No. Europe uses 868 MHz for UHF and the U.S. uses 915 MHz. Japan currently does not allow any use of the UHF spectrum for RFID. Government's also regulate the power of the readers to limit interference with other devices. Some groups, such as the Global Commerce Initiative, are trying to encourage governments to agree on frequencies and output. Tag and reader makers are also trying to develop systems that can work at more than one frequency, to get around the problem. Back to Top

I've heard that RFID doesn't work around metal and water. Does that mean I can't use it to track cans or liquid products?
No. Radio waves bounce off metal and are absorbed by water at higher frequencies. That makes tracking metal products or those with high water content problematic, but good system design and engineering can overcome this shortcoming. In fact, there are applications in which RFID tags are actually embedded in metal auto parts to track them. Back to Top

What's the difference between passive and active tags?
Active RFID tags have a battery, which is used to run the microchip's circuitry and to broadcast a signal to a reader (the way a cell phone transmits signals to a base station). Passive tags have no battery. Instead, they draw power from the reader, which sends out electromagnetic waves that induce a current in the tag's antenna. Semi-passive tags use a battery to run the chip's circuitry, but communicate by drawing power from the reader. Active and semi-passive tags are useful for tracking high-value goods that need to be scanned over long ranges, such as railway cars on a track, but they cost a dollar or more, making them too expensive to put on low-cost items. The Auto-ID Center is focusing on passive tags, which cost under a dollar today. Their read range isn't as far - less than ten feet vs. 100 feet or more for active tags - but they are far less expensive than active tags and require no maintenance. Back to Top

How much information can the tag store?
It depends on the vendor and the application, but typically a tag would carry no more than 2KB of data – enough to store some basic information about the item it is on. Back to Top

What's the difference between read-only and read/write tags?
Chips in RF tags can be read-write or read-only. With read-write chips, you can add information to the tag or write over existing information when the tag is within range of a reader, or interrogator. Read-write tags are useful in some specialized applications, but since they are more expensive than read-only chips, they are impractical for tracking inexpensive items. Some read-only microchips have information stored on them during the manufacturing process. The information on such chips can never been changed. A more flexible option is to use something called electrically erasable programmable read-only memory, or EEPROM. With EEPROM, the data can be overwritten using a special electronic process. Back to Top

What is reader collision?
One problem encountered with RFID is the signal from one reader can interfere with the signal from another where coverage overlaps. This is called reader collision. One way to avoid the problem is to use a technique called time division multiple access, or TDMA. In simple terms, the readers are instructed to read at different times, rather than both trying to read at the same time. This ensures that they don't interfere with each other. But it means any RFID tag in an area where two readers overlap will be read twice. So the system has to be set up so that if one reader reads a tag another reader does not read it again. Back to Top

What is tag collision?
Another problem readers have is reading a lot of chips in the same field. Tag collision occurs when more than one chip reflects back a signal at the same time, confusing the reader. Different vendors have developed different systems for having the tags respond to the reader one at a time. Since they can be read in milliseconds, it appears that all the tags are being read simultaneously. Back to Top

What is the read range for a typical RFID tag?
The read range of passive tags depends on many factors: the frequency of operation, the power of the reader, interference from metal objects or other RF devices. In general, low-frequency tags are read from a foot or less. High frequency tags are read from about three feet and UHF tags are read from 10 to 20 feet. Where longer ranges are needed, such as for tracking railway cars, active tags use batteries to boost read ranges to 300 feet or more. Back to Top

Are there any standards for RFID?
Yes. International standards have been adopted for some very specific applications, such as tracking animals. Many other standards initiatives are under way. The most interesting efforts involve GTag, which is promoted by EAN and UCC as a way to communicate with UHF tags; ISO 18000-6, which is an international effort that forms the foundation for the GTag standard; and the Auto-ID Center's electronic product code. The EPC and the technology surrounding it is not a standard in any formal way, but the Auto-ID Center hopes that it will be widely adopted and become the de facto standard. Back to Top

Who are the leading RFID vendors?
There are many different RFID vendors with different areas of expertise. We have compiled a director of vendors around the world. Click on Find a Vendor in the left-hand navigation bar to locate the type of vendor you are looking for. Back to Top

What are some of the most common applications for RFID?
RFID is used for everything from tracking cows and pets to triggering equipment down oil wells. It may sound trite, but the applications are limited only by people's imagination. The most common applications are tracking goods in the supply chain, tracking assets, tracking parts moving to a manufacturing production line, security (including controlling access to buildings and networks) and paymant systems that let customers pay for items without using cash. Back to Top

I've heard RFID can be used with sensors. Is that true?
Yes. Some companies are combining RFID tags with radiation sensors. One day, the same tags used to track items moving through the supply chain may also alert staff if they are not stored at the right temperature, if meat has gone bad, or even if someone has injected a biological agent into food.

What are intelligent software agents and how do they fit into RFID?
Software agents are basically autonomous applications that automate decision making by establishing a set of rules. For instance, if X happens, do Y. They are important to RFID because humans will be overwhelmed by the amount of data coming from RFID tags and the speed at which it comes (real-time in many cases). So agents will likely be used to automate routine decisions and alert employees when a situation requires their attention. SAP and a company called BiosGroup are working on an automated replenishment system in which software agents would make decisions when trends indicate a product will be out of stock.

What is "energy harvesting"?
Most passive RFID tags simply reflect back waves from the reader. Energy harvesting is a technique in which energy from the reader is gathered by the tagged, stored momentarily and transmitted back at a different frequency. This method may improve the performance of passive RFID tags dramatically.

Glossary of RFID Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A Active tag: An RFID tag that comes with a battery that is used to power the microchip's circuitry and transmit a signal to a reader. Active tags can be read from 100 feet or more away, but they're expensive – more than $20 each. They're used for tracking expensive items over long ranges. For instance, the US military uses active tags to track containers of supplies arriving in ports. Amplitude: The maximum absolute value of a periodic curve measured along its vertical axis (the height of a wave, in layman's terms). Antenna: The antenna is the conductive element that enables the tag to send and receive data. Passive tags usually have a coiled antenna that couples with the coiled antenna of the reader to form a magnetic field. The tag draws power from this field. Anti-collision: A general term used to cover methods of preventing radio waves from one device from interfering with radio waves from another. Anti-collision algorithms are also used to read more than one tag in the same reader's field. Auto-ID Center: A non-profit collaboration between private companies and academia that is pioneering the development of an Internet-like infrastructure for tracking goods globally through the use of RFID tags. Automatic Identification: Sometimes called automatic data capture. These are methods of collecting data and entering it directly into computer systems without human involvement. Technologies normally considered part of auto-id include bar codes, biometrics, RFID and voice recognition. B return to top Back scatter: A method of communication between tags and readers. RFID tags using back-scatter technology reflect back to the reader a portion of the radio waves that reach them. The reflected signal is modulated to transmit data. Tags using back scatter technology can be either passive or active, but either way, they are more expensive than tags that use inductive coupling . Bar code: A standard method of identifying the manufacturer and product category of a particular item. The barcode was adopted in the 1970s because the bars were easier for machines to read than optical characters. Barcodes' main drawbacks are they don't identify unique items and scanners have to have line of sight to read them. C return to top Contactless smart card: An awkward name for a credit card or loyalty card that contains an RFID chip to transmit information to a reader without having to be swiped through a reader. Such cards can speed checkout, providing consumers with more convenience. Chipless RFID tag: An RFID tag that doesn't depend on an integrate microchip. Instead, the tag uses materials that reflect back a portion of the radio waves beamed at them. A computer takes a snapshot of the waves beamed back and uses it like a fingerprint to identify the object with the tag. Companies are experimenting with embedding RF reflecting fibers in paper to prevent unauthorized photocopying of certain documents. But chipless tags are not useful in the supply chain, because even though they are inexpensive, they can't communicate a unique serial number that can be stored in a database. Closed-loop systems: RFID tracking systems set up within a company. Since the tracked item never leaves the company's control, it does not need to worry about using technology based on open standards. Coupling: See inductive coupling D return to top Die: The silicon block onto which circuits have been etched. E return to top EEPROM (Electrically Erasable Programmable Read-Only Memory): A non-volatile storage device on microchips. Usually bytes can be erased and reprogrammed individually. RFID tags that use EEPROM are more expensive than factory programmed tags , but they offer more flexibility because the end user can write an ID number to the tag at the time the tag is going to be used. Electromagnetic compatibility (EMC): The ability of a system or product to function properly in environment where other electromagnetic devices are used and not be a source itself of electromagnetic interference. Electromagnetic interferance (EMI): Interference caused when the radio waves of one device distort the waves of another. Cells phones, wireless computers and even robots in factories can produce radio waves that interfere with RFID tags. Electronic article surveillance (EAS): Simple electronic tags that can be turned on or off. When an item is purchased (or borrowed from a library), the tag is turned off. When someone passes a gate area holding an item with a tag that hasn't been turned off, an alarm sounds. EAS tags are embedded in the packaging of most pharmaceuticals. Electronic Product Code: (EPC): A 96-bit code, created by the Auto-ID Center , that will one day replace barcodes. The EPC has digits to identify the manufacturer, product category and the individual item. It is backed by the United Code Council and EAN International, the two main bodies that oversee barcode standards. Error correcting code: A code stored on an RFID tag to enable the reader to figure out the value of missing or garbled bits of data. It's needed because a reader might misinterpret some data from the tag and think a Rolex watch is actually a pair of socks. Error correcting mode: A mode of data transmission between the tag and reader in which errors or missing data is automatically corrected. Error correcting protocol: A set of rules used by readers to interpret data correctly from the tag. European Article Numbering (EAN): The bar code standard used throughout Europe, Asia and South America. It is administered by EAN International. Excite: The reader is said to "excite" a passive tag when the reader transmits RF energy to wake up the tag and enable it to transmit back. eXtensible markup language (XML): A widely accepted way of sharing information over the Internet in a way that computers can use, regardless of their operating system. F return to top Factory programming: Some read-only have to have their identification number written into the silicon microchip at the time the chip is made. The process of writing the number into the chip is called factory programming. Field programming: Tags that use EEPROM , or non-volatile memory, can be programmed after it is shipped from the factory. Fluidic Self-Assembly: A manufacturing process, patented by Alien Technology . It involves flowing tiny microchips in a special fluid over a base with holes shaped to catch the chips. Frequency: The number of repetitions of a complete wave within one second. 1 Hz equals one complete waveform in one second. 1KHz equals 1,000 waves in a second. RFID tags use low , high , ultra-high and microwave frequencies. Each frequency has advantages and disadvantages that make them more suitable for some applications than for others. G return to top GTAG (Global Tag): A standardization initiative of the Uniform Code Council (UCC) and the European Article Numbering Association (EAN) for asset tracking and logistics based on radio frequency identification (RFID). The GTAG initiative is supported by Philips Semiconductors, Intermec, and Gemplus, three major RFID tag makers. H return to top High-frequency tags: They typically operate at 13.56 MHz. They can be read from about 10 feet away and transmit data faster. But they are consume more power than low-frequency tags. I return to top Inductive coupling: A method of transmitting data between tags and readers in which the antenna from the reader picks up changes in the tag's antenna. Industrial, Scientific, and Medical (ISM) bands: A group of unlicensed frequencies of the electromagnetic spectrum. Integrated circuit (IC): A microelectronic semiconductor device comprising many interconnected transistors and other components. Most RFID tags have ICs. Interrogator: See RFID reader . J return to top K return to top L return to top Low-frequency tags: They typically operate at 125 KHz. The main disadvantages of low-frequency tags are they have to be read from within three feet and the rate of data transfer is slow. But they are less expensive and less subject to interference than high- frequency tags . M return to top Memory: The amount of data that can be stored on a tag. Microwave tags: Radio frequency 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. Modulation: Changing the frequency or amplitude of a wave to transmit data that is converted into digital form. For example, a wave with the normal amplitude (or height) may be a one in binary code and a wave with a lower amplitude might be a zero. Multiple access schemes: Methods of increasing the amount of data that can be transmitted wirelessly within the same frequency spectrum. 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. N return to top NanoBlock: The term Alien Technology uses to describe its tiny microchips, which are about the width of three human hairs. Nominal range: The read range at which the tag can be read reliably. 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. O return to top Object Name Service (ONS): 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. P return to top Passive tag: An RFID tag without a battery. When radio waves from the reader reach the chip's antenna, it creates a magnetic field. The tag draws power from the field and is able to send back information stored on the chip. Today, simple passive tags cost around 50 cents to several dollars. Patch antenna: A small square antenna made from a solid piece of metal or foil. Physical Markup Language (PML): 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. PML Server: A server that responds to requests for Physical Markup Language (PML) files related to individual Electronic Product Codes . The PML files and servers will be maintained by the manufacturer of the item. Power level: The amount of RF energy radiated from a reader or an active tag. The higher the power output, the longer the read range, but most governments regulate power levels to avoid interference with other devices. Programming: Writing data to an RFID tag. 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. Q return to top R return to top Radio Frequency Identification (RFID): 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. Range: See read range . Read: The process of turning radio waves from a tag into bits of information that can be used by computer systems. Read rate: The maximum rate at which data can be read from a tag expressed in bits or bytes per second. Reader (also called an interrogator): The reader communicates with the RFID tag via radio waves and passes the information in digital form to a computer system. Reader field: The area of coverage. Tags outside the reader field do not receive radio waves and can't be read. Read-only tags: Tags that contain data that cannot be changed unless the microchip is reprogrammed electronically. 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 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 (see above), which requires the tag to be within a few feet of the reader. Read-write tags: RFID tags that can store new information on its microchip. San Francisco International Airport uses a read-write tag for security. When a bag is scanned for explosives, the information on the tag is changed to indicate it has been checked. The tag is scanned again before it is loaded on a plane. Read-write tags are more expensive than read only tags, and therefore are of limited use for supply chain tracking. RFID tag: A microchip attached to an antenna that 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 are stuck on boxes; smart cards and key-chain wands for paying for things; and a box that you stick on your windshield to enable you to pay tolls without stopping. RFID tags can be active tags, passive tags and semi-passive tags. S return to top 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. Semi-passive tag: Similar to active tags , but the battery is used to run the microchip's circuitry but not to communicate with 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 cost a dollar or more. Sensor: A device that responds to a physical stimulus and produces an electronic signal. Sensors are increasingly being combined with RFID tags to detect the presence of a stimulus at an identifiable location. Silent Commerce: This term covers all business solutions enabled by tagging, tracking, sensing and other technologies, including RFID, which make everyday objects intelligent and interactive. When combined with continuous and pervasive Internet connectivity, they form a new infrastructure that enables companies to collect data and deliver services without human interaction. Smart label: A label that contains an RFID tag. It's considered "smart" because it can store information, such as a unique serial number, and communicate with a reader. Smart cards: See contactless smart cards . T return to top Tag: See RFID Tag Time Division Multiple Access (TDMA): A method of solving the problem of the signals of two readers colliding. Algorithms are used to make sure the readers attempt to read tags at different times. Transponder: A radio transmitter-receiver that is activated when it receives a predetermined signal. RFID tags are sometimes referred to as transponders. U return to top Ultra-high frequency (UHF): Typically, tags that operate between 866 MHz to 930 MHz. They can send information faster and farther than high- and low-frequency tags. But radio waves don't pass through items with high water content, such as fruit, at these frequencies. UHF tags are also more expensive than low-frequency tags, and they use more power. Uniform Code Council (UCC): The nonprofit organization that overseas the Uniform Product Code, the barcode standard used in North America. Uniform Product Code (UPC): The barcode standard used in North America. It is administered by the Uniform Code Council. V W Write rate: The rate at which information is transferred to a tag, written into the tag's memory and verified as being correct. X return to top XML: See eXtensible Markup Language . XML Query Language (XQL): A method of querying a database based on XML. Files created using the Auto-ID Center's Physical Markup Language can be searched using XQL. Y Z