Depending on the frequency that is used and its performance, an RFID reader sends radio waves of between one centimeter and 30 meters or more. If a transponder enters this electromagnetic region, it detects the activating signal from the reader. The RFID reader decodes the data stored in the integrated circuit of the transponder (silicon chip), and communicates them, depending on the application, to a host system.
The majority of these devices can both read and write, so data transfer will also work in the reverse direction from the system to the data medium or tag.
The reader is consequently the major component of the system, responsible for activating the transponder and thus for initiating data communication.
RFID readers are differentiated by their features, the main ones being stationary or mobile.
Stationary devices are intended for firm incorporation in existing systems, and are the commonest type found. The necessary antenna is attached through an interface. Detected data can be conducted to a host on standard interfaces like RS232, Ethernet or USB.
Mobile readers serve for detecting data on various objects and are notable for their compactness. The antenna is integrated in the device or directly attached to it. Data transfer to a host uses wireless standards like WLAN or DECT.