Near-field communication uses low-frequency waves to communicate between two antennae at very short ranges under a few inches. One example of this technology uses a cellphone to transmit a weak radio signal to a magnetic tag embedded in a nearby poster, piece of merchandise or electronic pay device. The active device, or the cellphone, generates a small magnetic field, whereas the passive tag in the object reacts to that field.
The magnetic fields between the active and passive near-field communication devices create a weak radio transmission. Special applications on smartphones decode the radio signal generated between the phone and the tag to provide information to the user. Near-field communication allows just one transmission at a time because of the short distances involved.
When two active devices get near each other, information is often exchanged. For instance, when two cellphones with the same near-field communication app get close to each other, vital contact information may be exchanged in just a few seconds. This type of active communication obviates the need for verbal communication of contact information, which may take a few minutes rather than a few seconds. Eavesdropping on near-field communications is highly unlikely due to the short distances required for the transmission.
Near-field communication technology is based on radio frequency ID tags that use inductive coupling to transmit information. Inductive coupling creates a magnetic field between two objects to cause electrons to flow through a conductor.