Patent ID: 8466773

Claim:
A method for granting access to a restricted area, said method comprising the steps of: transmitting by a user of a portable radio terminal a request to a central computer for an access code to enable access by the user to a restricted area wherein the central computer contains access codes and contains information corresponding with the identity of at least one of authorized users of the restricted area and of portable radio terminals authorized to obtain access to the restricted area; verifying in the central computer that information corresponding with at least one of the identity of the user of the portable radio terminal and the identity of the portable radio terminal included with the request received by it from the portable radio terminal corresponds with stored identification information in the central computer relative to allowed access to the restricted area by authorized users and by authorized portable radio terminals; after verification in the central computer of allowed access by at least one of the user and the portable radio terminal, transmitting from the central computer via radio waves a stored access code to the portable radio terminal possessed by the user; transmitting from the portable radio terminal over a short-range radio link to a transmitter unit associated with the restricted area to which access is sought by the user the access code received by the portable radio terminal from the central computer; transmitting to the central computer from the transmitter unit associated with the restricted area the access code received by the transmitter unit from the portable radio terminal; and comparing in the central computer the access code received from the transmitter unit associated with the restricted area with the stored access code that the central computer transmitted to the portable radio terminal, to allow access to the restricted area by the user of the portable radio terminal when the access code received from the transmitter unit associated with the restricted area corresponds with the stored access code that was transmitted by the central computer to the portable radio terminal, thereby creating a closed circuit for comparing an access code transmitted by the central computer with an access code received by the central computer, wherein the closed circuit is created by sequentially transmitting the access code from the central computer to provide the access code to the portable radio terminal as a received access code, by transmitting the received access code from the portable radio terminal to provide the received access code to the restricted area, and by transmitting the received access code from the restricted area to the central computer for comparison with the transmitted access code.