Patent ID: 7149556

Claim:
A radio frequency (RF) device for authorizing user access to portions of a computer system composing: a power supply; processing circuitry that accesses the power supply according to a location of the RF device; an antenna tat transmits communication signals from the processing circuitry to a transponder that is coupled to the computer system; the processing circuitry being configured to operate at a first power level while the RF device is located outside a first range of the transponder, until the communication signals indicate that the location of the RF device is within the first range of the transponder, the processing circuitry being configured to begin operations at a second power level in response to detecting that the RF device has moved within the first range of the transponder; and the processing circuitry being configured to operate at the second power level until the communication signals indicate that the location of the RE device has moved outside of a second range from the transponder, the second range greater than the first range.