"...An RFID system is based around a reader and a tag. A tag stores information, whereas an RFID reader retrieves or modifies information stored on the tag. To transmit this information through the air, both devices use high frequency electric current oscillations (the frequency of such current oscillations is also known as radio frequency or RF) which when applied to a piece of wire (referred to as an antenna) have a tendency to extend themselves well beyond the actual antenna wire boundary in the form of electromagnetic waves.
Such waves consist of two parts; magnetic and electric. Each of these contributing parts has an area of influence which depends on the distance from the emitting antenna. Another important feature of the waves is their ability to induce electric charge or current in a conductor placed in the path of such wave propagation. If a tag is placed in the path of an electromagnetic wave emitted by a reader, there will most certainly be electric current induced in the tag's antenna. Also, the direction of propagation can be roughly controlled by the shape of the emitting antenna, although in reality waves tend to scatter among a multitude of directions..."
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Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer