In an information access system, an active contactless information storage device senses a carrier of an RF signal at a first frequency in first predetermined periods occurring in a predetermined cycle and senses a carrier of an RF signal at a second frequency in second predetermined periods occurring in the predetermined cycle. When the storage device senses and detects a carrier of an RF signal at one of the first and second frequencies in a particular predetermined period, it receives further an ID request signal, and, in response to the ID request signal, transmits a response signal at a corresponding one of the third and fourth frequencies that carries an ID of the active contactless information storage device. This reduces possible interference between reader/writer devices for communicating with the information storage device.
