RFID readers, also called interrogators, first and foremost are used to query RFID tags in order to obtain identification, location, and other information about the device or product the tag is embedded in. The RF energy from the reader antenna is collected by the RFID tag antenna and used to power up the microchip. There are two types of RFID readers:
RFID read-only readers. As the name suggests, these devices can only query or read information from a nearby RFID tag. These readers are found in fixed, stationery applications as well as portable, handheld varieties.
RFID read-write readers. Also known as encoders, these devices read and also write (change) information in an RFID tag. Such RFID encoders can be used to program information into a "blank" RFID tag. A common application is to combine such a RFID reader with a barcode printer to print "smart labels". Smart labels contain a UPC bar code on the front with an RFID tag embedded on the back.
Readers can receive information from tags via cellular, HF/NFC, WiFi, USB, Bluetooth, WWAN, or POE (Power Over Ethernet) in a fixed or handheld format. Some readers feature integrated antennas, which can also be linear or circular polarized.