Abstract: A radio telephone system has a plurality of base stations 3, 4 and a plurality of mobile radios. The position of the mobile radios are determined by combining information at the base stations 3, 4 with information from additional position indicators, such as beacons 16a, 16b, 16c placed at intervals alongside a railway track 8. This enhanced information on the positions of the mobile radios enables channels to be reused on mobile radios with less physical separation than hitherto, thereby improving the efficiency of channel allocation.

Abstract: Radio telephone apparatus for use in an underground railway system comprises two base stations 3, 4 respectively located at successive railway stations 1, 2. The base station 3 feeds a radiating cable 7 extending in the tunnel bore towards the base station 4 which feeds a radiating cable 12 extending in the tunnel bore towards the base station 3. When a train travels from the station 1 to the station 2, the mobile radio on the train effects call handover, ie transference of communication with cable 7 to communication with cable 12. To ensure no interruption in a call during handover, an attenuator 16 is incorporated in the cable 7 adjacent its end, such that the mobile radio effects call handover to the cable 12 before losing communication with the cable 7, even at the maximum possible speed of the train.

Abstract: A radio telephone system is installed in an underground railway system. The telephone system has base stations A, B at respective railway stations 1, 2 and the base stations serve leaky cables serving the railway stations and further cables extending along the tunnel bores interconnecting the railway stations. To improve the availability of channels available as station calls to users of mobile radios within the areas of the railway stations, switches 20 are incorporated to prevent any channel occupied as a station call being directed into the cable serving the tunnel. This enables channels allocated as train call channels at one base station to be re-used as station call channels at an adjacent base station.