For example, in cards used by occupants of a condominium…?
There is no battery in the cards used to enter a building. The reader emits radio waves, which the transponder in the card captures and uses to reflect back a signal. This is what is known as a passive RFID tag or transponder.
—Mark Roberti, Founder and Editor, RFID Journal
Is Killing an RFID Tag at the Point of Sale a Good Idea? »