Tiny radios in your pocket

     Did you ever wonder how that hotel room key card works, when it never enters a slot and doesn’t even have to leave the cardboard sleeve? It is a technology called a Radio Frequency Identification (RFID) tag.  An RFID tag is really a tiny radio that can both transmit and receive data that is stored in a memory device on the card. 

Photo by Scott Hamilton RFID tag from laser printer toner
cartridge used to track cartridge life.

     The RFID tag is less than a hundredth of an inch in size, and usually has an antenna attached that is around a tenth of an inch in size. Sometimes the antenna is larger to make it possible to read the card from a longer distance. RFID tags can store digital information much like a USB drive or computer hard-drive. The real difference is that they are much smaller, cannot store very large amounts of information, and can be read and written to without a physical connection to the reader/writer.

     Most modern hotels use RFID cards to secure their rooms because they can modify the code on both the card and the lock randomly for every visitor to the hotel, greatly increasing the security of the rooms. Other uses of RFID tags are product tracking and security, inventory, and theft prevention. 

     The technology used in these products was originally created to assist large cattle ranches in tracking and identifying cattle. It is now used to track products in every industry and may eventually replace the bar code seen on products today. The main advantage of RFID is that a system can read multiple tags simultaneously without physically making contact with or seeing the tag. 

     RFID tags can make the future of grocery store checkout as simple as walking through a gate with your cart full of groceries and your debit card. The gate is a large RFID reader that will seemingly instantaneously read the tags in all the products in your cart and the tag in your bank card. The system will charge your card, e-mail your receipt, and you are on your way.

     RFID technology has been around since 1970, but only recently has become inexpensive enough to produce that it has come into wide use. The early technology used inductive coupling, which basically means that it used complicated metal coils that reacted in a specific way with a magnetic field, creating a specific current, or radio signal. This technology was difficult to manufacture and every tag had a unique shape and design. 

     The inductive designs were replaced by capacitive coupled tags, which used conductive carbon ink to create disposable tags that could be printed on-demand. This new technology used a microchip to store just 96-bits of information. This technology was not widely adopted and the company that developed it shut down in 2001.

     The latest innovations in RFID technology have combined the two methods to create a robust tag system that can either be constantly powered by an integrated battery (active); powered on demand with an integrated battery (semi-active); and powered by proximity to the reader (passive). 

     Active and semi-active tags are the most expensive and used to track expensive equipment like railroad cars and truckloads of inventory. They can be read from more than twenty feet away and are not considered disposable. When a product connected to an active RFID tag, like a railway car, is retired, the tag is moved to another product.

     Passive RFID tags are used in everything from your toll road pass sticker on your car windshield and your hotel room key to the bottle of shampoo you bought last week at the store. The tags can either be write-once-read-many, or read-write tags. You can get applications for your smartphone that can read, store, and simulate RFID tags. If you want to play around with RFID technology, old hotel room keys can usually be rewritten with card writer applications. You can then use them to automatically start applications on your phone, like turning on Pandora when it detects the tag in your car. You can also copy the RFID tag from your room key to your cell phone and use your phone as a room key. RFID technologies are coming en masse to our lives and I leave it to you to decide if this is good or bad.