of the conventional radio receivers on the mobile tags the mobile tags are programmed not to transmit uwb signals unless they can detect the presence of the surrounding infrastructure by checking for receipt of the hailing signal via the conventional radio channel therefore the tag will not transmit uwb signals outside of the building in which the location system is installed and the location system is able to advantage of any relaxed regulations concerning indoor only uwb systems in a further aspect of the proposed location system each tag is equipped with a uwb transmitter and a conventional radio transceiver and each base station is equipped with a uwb receiver and a conventional radio transceiver tags in such a system can both receive messages from and send messages to the associated infrastructure components via the conventional radio link this arrangement has the advantage that it is possible to track many tags in the location system the system can employ uwb technology which is not capable of coding the identity of the transmitting tag in the uwb signal emitted by a tag whilst still allowing base stations to identify tags within the system the tag simultaneously transmits its identifier on the conventional radio channel together with an uncoded uwb signal a base station receiving a uwb signal can ascribe it to the correct tag by associating that signal with the conventional radio message which it will receive at the same time a tag suitable for use in the location system is illustrated in fig2 the tag 2 comprises a tag controller 4 for example a pic16lf877a microcontroller made by microchip inc a uwb transmitter 6 and a conventional radio transceiver 8 such as the cc1020 made by chipcon.