An RFID reader is a technological apparatus, which, depending on its design and purpose, either produces a magnetic alternating field of low range or high frequency radio waves.
If an RFID transponder gets into the electromagnetic field produced by the reader, coupling will take place with the reader, which enables the RFID transponder to be read out. The reading process is controlled by software on the reader. This usually has interfaces to other computer systems. Depending on the design, it is also possible to describe transponders and thereby modify information saved on the chip.
Modern RFID readers are able to read several transponders at the same time. This group capacity is a central advantage of RFID technology compared to other processes for identifying objects – for example, identification via a barcode.
To enable RFID readers to communicate with several tags at the same time, various anti-collision processes have been developed, in which transponders are allocated different access times or frequencies, for example. This should prevent interference of the signals.