Patent ID: 7176783

Claim:
A device for identifying authentic information and enabling an action, comprising: a) a base unit and a key unit transmitting information to the base unit, the base unit detecting the information and comparing it with predetermined information, the base unit enabling the action when the detected information matches the predetermined information; b) the base unit and the key unit include respective accurately-timed digital generators running essentially synchronously with respect to one another and generating digital output information that changes at predetermined time intervals; c) the key unit combining the digital information of the key unit digital generator with a stored identification code in accordance with a predetermined coding rule to form a coded information item, the key unit including: a central evaluating and control unit controlling the key unit digital generator; an identification code memory; a coding unit; and a ring-connected shift register, the shift register being loaded at predetermined time intervals with a different coded information item generated by the coding unit using the digital information from the key unit digital generator and contents of the identification code memory, and the shift register cyclically reading out the different coded information items, the cyclical readings output from the shift register are supplied as an input signal to a frequency modulator, the frequency modulator generating an auxiliary-carrier frequency which is a multiple below the frequency of the radio-frequency generator of the base unit and a multiple above the cycles of the shift register, and the auxiliary-carrier frequency is supplied to the controllable electronic switch; d) the base unit using the predetermined coding rule to code the predetermined information with the digital information of the base unit digital generator to form a predetermined coded information item, and comparing the predetermined coded information item with the coded information item communicated by the key unit, the base unit enabling the action when the coded information item communicated matches the predetermined coded information item; e) the base unit transmitting a radio-frequency carrier signal; f) the key unit including a controllable electronic switch switching an antenna between an essentially matched state and a mismatched state in accordance with the coded information item, and the antenna reflecting the received radio-frequency carrier signal in accordance with the time changing digital coded information; and g) the base unit receiving and evaluating the reflected signal.