Passive tag with variable output

This invention relates to a passive RF information tag which provides status reports through a varying output. A passive RF tag receives a number of varying inputs. The RF tag is preferably associated with a vehicle, and the inputs are indicative of diagnostic information from a vehicle braking system. The passive RF tag receives a signal from a transmitter that causes the RF tag to query the current status of the several inputs. The RF tag then sends a signal back to the transmitter/receiver indicative of the current status.