A mobile object monitoring system

A mobile object monitoring and tracking system includes a tracking unit 10 which is fitted to a mobile object. The unit 10 comprises a GSM transceiver 16 for receiving mobile object locating signals from and transmitting mobile object identification signals to an array of GSM sites in a GSM-based area network defining a broad area of coverage. The unit 10 further includes a signpost receiver 20 for receiving mobile object locating signals from a strategically located array of signpost stations in a dedicated area network defining a restricted area of coverage falling within the broad area of coverage. The tracking unit is also provided with a transmitter 18 for transmitting mobile object location and identification signals to a central control station for identifying the mobile object and determining its approximate location. The system provides a number of activating inputs 26 for activating the tracking unit 10 and a number of arming inputs 28 for transmitting emergency signals to the unit 10.