Information access system and active-type contactless information storage device

An information access system for accessing information stored in a contactless information storage device, said information access system comprising:

• an active contactless information storage device having a memory, a first control unit, a battery, a timer for measuring time, first and second receiver units for sensing carriers of RF signals at first and second different frequencies for detection, and first and second transmitter units for transmitting respective response signals at third and fourth frequencies different from said first and second frequencies in response to reception of ID request signals,
• a first reader/writer device connected to an information processing apparatus, and having a second control unit, a third transmitter unit for cyclically transmitting an ID request signal at said first frequency under the control of said second control unit, and a third receiver unit adapted to be continuously ready to receive an RF signal at said third frequency, and
• a second reader/writer device connected to an information processing apparatus, and having a third control unit, a fourth transmitter unit for cyclically transmitting an ID request signal at said second frequency under the control of said third control unit, and a fourth receiver unit adapted to be continuously ready to receive an RF signal at said fourth frequency, wherein
• said first control unit controls said first and second receiver units to simultaneously sense carriers of RF signals at said first and second frequencies in predetermined periods occurring in a predetermined cycle,
• when said first receiver unit senses and detects a carrier of an RF signal at said first frequency in a particular predetermined period, said first control unit causes said first receiver unit to receive further the ID request signal, and, in response to the ID request signal, causes said first transmitter unit to transmit a response signal at said third frequency corresponding to said first frequency that carries an ID of said active contactless information storage device stored in said memory;
• when said second receiver unit senses and detects a carrier of an RF signal at said second frequency in the particular predetermined period, said first control unit causes said second receiver unit to receive further the ID request signal, and, in response to the ID request signal, causes said second transmitter unit to transmit a response signal at said fourth frequency corresponding to said second frequency that carries an ID of said active contactless information storage device stored in said memory;
• in the carrier sensing, said first control unit causes said first and second receiver units to be in an active state and said first and second transmitter units to be in an inactive state in the particular predetermined period and a subsequent predetermined period;
• when said first receiver unit attempts to sense a carrier of an RF signal at said first frequency in the particular predetermined period but detects no carrier, said first control unit controls said first receiver unit and said first transmitter unit to maintain the inactive state during a non-carrier sensing period between the particular predetermined period for carrier sensing and the subsequent predetermined period for subsequent carrier sensing;
• and
• when said second receiver unit attempts to sense a carrier of an RF signal at said second frequency in the particular predetermined period but detects no carrier, said first control unit controls said second receiver unit and said second transmitter unit to maintain the inactive state during a non-carrier sensing period between the particular predetermined period for carrier sensing and the subsequent predetermined period for subsequent carrier sensing.

An active contactless information storage device comprising:

• a memory,
• a battery,
• a timer for measuring time,
• a receiver unit for sensing and detecting carriers of RF signals at first and second different frequencies from a first or second reader/writer device in respective predetermined periods, when said active contactless information storage device is in a communication range of said first or second reader/writer device,
• a transmitter unit for transmitting a response signal at a third or fourth frequency different from said first and second frequencies, when said receiver unit receives an ID request signal, and
• a control unit for controlling said receiver unit and said transmitter unit, wherein
• said control unit controls said receiver unit to sense a carrier of an RF signal at said first frequency in first predetermined periods occurring in a predetermined cycle and sense a carrier of an RF signal at said second frequency in second predetermined periods occurring in said predetermined cycle;
• when said receiver unit senses and detects a carrier of an RF signal at one of said first and second frequencies in a particular predetermined period, said control unit causes said receiver unit to receive further the ID request signal, and, in response to the ID request signal, causes said transmitter unit to transmit a response signal at a corresponding one of said third and fourth frequencies that carries an ID of said active contactless information storage device stored in said memory;
• in the carrier sensing, said control unit causes said receiver unit to be in an active state and said transmitter unit to be in an inactive state in the first and second predetermined periods;
• and
• when said receiver unit attempts to sense a carrier of an RF signal at said first frequency in the first predetermined period but detects no carrier, said control unit controls said receiver unit and said transmitter unit to maintain the inactive state during a non-carrier sensing period between the first predetermined period for carrier sensing and the second predetermined period for subsequent carrier sensing.

An active contactless information storage device comprising:

• a memory,
• a battery,
• a timer for measuring time,
• first and second receiver units for sensing and detecting, in the same predetermined period, carriers of RF signals at first and second different frequencies from a first or second reader/writer device, when said active contactless information storage device is in a communication range of said first or second reader/writer device,
• first and second transmitter units for transmitting respective response signals at respective third and fourth frequencies different from said first and second frequencies, when said first and second receiver units receive ID request signals, and
• a control unit for controlling said first and second receiver units and said first and second transmitter units, wherein
• said control unit controls said first and second receiver units to simultaneously sense carriers of RF signals at said first and second frequencies in predetermined periods occurring in a predetermined cycle;
• when said first receiver unit senses and detects a carrier of an RF signal at said first frequency in a particular predetermined period, said control unit causes said first receiver unit to receive further the ID request signal, and, in response to the ID request signal, causes said first transmitter unit to transmit a response signal correspondingly at said third frequency that carries the ID of said active contactless information storage device stored in said memory;
• when said second receiver unit senses and detects a carrier of an RF signal at said second frequency in the particular predetermined period, said control unit causes said second receiver unit to receive further the ID request signal, and, in response to the ID request signal, causes said second transmitter unit to transmit a response signal correspondingly at said fourth frequency that carries the ID of said active contactless information storage device stored in said memory;
• in the carrier sensing, said control unit causes said first and second receiver units to be in an active state and said first and second transmitter units to be in an inactive state in the particular predetermined period and a subsequent predetermined period;
• when said first receiver unit attempts to sense a carrier of an RF signal at said first frequency in the particular predetermined period but detected no carrier, said control unit controls said first receiver unit and said first transmitter unit to maintain the inactive state during a non-carrier sensing period between the particular predetermined period for carrier sensing and the subsequent predetermined period for subsequent carrier sensing;
• and
• when said second receiver unit attempts to sense a carrier of an RF signal at said second frequency in the particular predetermined period but detected no carrier, said control unit controls said second receiver unit and said second transmitter unit to maintain the inactive state during a non-carrier sensing period between the particular predetermined period for carrier sensing and the subsequent predetermined period for subsequent carrier sensing.