Bar code: a standard method of identifying items based on lines of varying widths and spacing are visually read by a scanner. Bar codes are a one-time use technology. Once the code is printed, information cannot be added to it and the code cannot be reused.

Closed loop: refers to an RFID system in which RF tags remain under the control of a single company. Because tags are continuously recycled, the cost of the tag is amortized over many process cycles. Closed-loop systems are typically used for higher value applications, such as assembly lines.

Inlay: an RF tag embedded within label material so that it can be attached directly to cartons, containers, parts bins, racks and totes.

Interface: the device that translates signals from the reader into a computer language and transfers that information to a PC or a PLC.

Open loop: refers to an RFID system in which tags must be compatible at different steps in the supply chain. Because tags typically are not reused, they are less expensive than in closed-loop applications. Open-loop systems are primarily used in retail and distribution environments.

Passive tag: an RF tag that draws its electrical power from radio waves. It lasts longer and is less expensive than an active tag. Passive tags are typically used in open-loop applications.

Range: the distance at which successful reading can be accomplished. In assembly applications, a short reading distance from 1 to 5 inches is often desired. However, in retail and distribution applications, a longer reading distance--up to 15 feet--is preferred.

Reader: the device that powers the antenna. It receives tag data from the antenna, then filters, boosts and transmits the data to the controller interface.

Read-only: refers to RF tags that cannot be changed unless the microchip is reprogrammed. Read-only tags are less expensive than read-write tags.

Read rate: the maximum rate at which data can be read from a tag expressed in bits or bytes per second.

Read-write: refers to RF tags that can receive new data while they are attached to product, such as tags that store a record of shipment information or track work in progress. They are often used on reusable containers, parts bins, racks and carriers found along assembly lines. When the contents of a container or carrier are changed, new information is written to the tag.

RFID: an acronym for "radio frequency identification." An RFID system uses radio frequency waves to transfer data between a reader and items that have RF tags affixed. Unlike bar codes, RFID systems offer enhanced data collection advantages, such as the ability to read without a direct view of a tag.

RF portal: the effective broadcast area of the antenna.

RF tag: also known as a transponder or data carrier, each RF tag consists of a memory chip, a substrate and an antenna. Unlike printed codes, RF tags can be reused and they can withstand harsh environments. Tags come in many different sizes and shapes, and are typically used for either product identification or carrier identification.