Patent ID: 8310379

Claim:
A monitoring device for a tracking system adapted for use in at least one vehicle, comprising: a communication circuit adapted for communication with at least one radio frequency identification (RFID) tag on an article to be transported by the vehicle; a position system (PS) circuit adapted for determining a location of the vehicle; a control circuit having a microprocessor and a memory, the control circuit being electrically connected to the communication circuit and the PS circuit, the microprocessor being adapted to acquire the RFID tag data and the location data in the memory, to operate the communication circuit to interrogate the RFID tag, to operate the PS circuit to determine a location of the vehicle, and to associate the RFID tag data with the location data of the vehicle; an alarm electrically connected to the microprocessor; and whereas the monitoring device is adapted to determine or approximate the distance of the RFID tag from the monitoring device based on a time delay in receiving the RFID tag's response to interrogation and to activate the alarm if a distance threshold of the RFID tag from the monitoring device is exceeded, whereas this distance threshold is lower than the maximum physical range of the RFID tag, wherein the microprocessor is arranged to perform a threshold test before an alarm is set, wherein the threshold test determines if the RFID tag has failed to respond to a predetermined number of consecutive interrogations or has failed to respond to interrogation for a predetermined time interval.