Use of a portable identifier with two communication protocols

Abstract

Described is a method for using a portable identifier to communicate with a vehicle system using a first communication protocol and a second communication protocol. The portable identifier includes an electrical energy source. The method includes determining the remaining energy level in the electrical energy source, measuring the temperature, detecting that the determined remaining energy level is below a predetermined energy threshold and that the measured temperature is below a predetermined temperature threshold, and then changing the communication from the first communication protocol to the second communication protocol. The second communication protocol is configured so that the voltage across the terminal of the electrical power source remains above a predetermined voltage threshold.

Dependencies are inferred from the claim text.