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

RFID is a generic term that refers to more than just the cheap tags that companies slap onto pallets to comply with retailers' edicts. 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, so they have a range of just a couple of metres. A reader must "wake them up", at which point they transmit the little bit of data that they hold. The orientation of a passive tag must be just right or the reader won't find it. 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 100 metres, are battery-powered, and can either transmit constantly or be activated by an actuator. Two major suppliers of active tags are Axcess and WhereNet.

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. For example, 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.

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.

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.