Car navigation,car gps vehicle tracker VT310,fleet management system Listen-in Two-way Audio Inbuilt Tremble Sensor ... SOS help Car navigation,car gps vehicle tracker VT310,fleet management system Features:Track by SMS/GPRSTrack on Mobile PhoneListen ... start: 42 sec., averageAltitude Limit: 18,000 meters (60,000 feet) max.Velocity Limit: 515 meters/second (1000 knots) max.LED ...