The TyreGuard 400 Booster / Repeater is designed to enhance the signals from the sensors to the monitor should the vehicle that the TPMS is fitted to exceeds 8.0 meters. While the system has been tested and will function up to 18 meters (60 ft), there may be occasions where a vehicle will emit electronic interference causing the loss of signal from the sensors. The chance of losing signals increases with distance (monitor to rear tires), extreme cold and battery deterioration.