Remember the old Hallmark cards slogan, "when you care enough to send the very best"? When it comes to RFID, there may be a similar message in the offing.

Two main types of tag
RFID is a generic term that refers to more than just the cheap tags that companies slap onto pallets to comply with the edicts of retailers like Wal-Mart, Tesco and Marks & Spencer. In actuality, there are many types of RFID systems. Wal-Mart requires passive RFID tags. But the "very best" for your company's needs may be active RFID tags and the infrastructure that supports them.

    Passive tags are not powered, and must be "woken up" by a reader that is only a few feet away. The current generated in the tag's antenna by the signal from the reader is just enough for the tag to transmit the little bit of data that it holds - but it has a very short range. The orientation of a passive tag must be just right or the reader won't find it (as it won't generate enough signal in the antenna). Passive tags also have difficulty sending data through liquids or metal.

  • Active tags, on the other hand, can have a range of as far as 300 feet, are battery-powered, and can either transmit constantly or be activated by a signal from the reader. Two major suppliers of active tags are Axcess and WhereNet. Each has carved out a slightly different, but at times overlapping, niche for its business.

Get the right tag for your application
Both active and passive tags allow data to be captured and put into a database. Add business rules that relate to the tag or groups of tags, and presto! A higher-level application is created. The difference between active and passive is in the kinds of applications the enterprise can build on top of the information that each transmits.

Active tags shine in high-velocity, chaotic environments, according to Tim Harrington, vice president of product strategy at WhereNet. One WhereNet customer handles 60,000 incoming and 40,000 outbound shipping containers every year. Because there can be 2,000 gate moves per day at the height of the buying season, passive tags would be useless; each truck would have to stop and get scanned. With active tags, however, the trucks roll in and out. And not only does the manager know when each container has arrived, but even in a yard hundreds of acres large, he knows exactly where everything is at all times.

Snooping and security needs active tags
Chaos isn't confined to containers, however. Axcess has its active tags deployed at a Las Vegas casino, where waiters and waitresses are tagged for the purpose of time and motion studies. Allan Griebenow, CEO and president of Axcess, says the casino uses the tags to measure the time it takes to complete a cycle of taking, picking up, and delivering an order so that managers can add staff when needed.

Active tags can also be used for security. A laptop, for example, might be tagged and associated with an employee pass card. If the two don't match as the employee goes through an exit, an alert can be triggered. A passive tag won't work in this case because there is no way of ensuring that the tag will be read as it passes the reader (and it would be easy for a thief to ensure that it is not read).

Both companies also have customers in the health care industry, where tags are used on patients and hospital equipment alike.

Passive may save money, but lose in the long term
Before you decide to deploy an RFID system, think about your company's long-term needs. Passive tags are less expensive, but sometimes a situation calls for the very best. If you start with less-expensive passive tags only to discover that what you really wanted were the more capable active tags, you'll end up spending more or having to settle for a limited solution.