British Rail's distributed Band III radio network

摘要

British Rail (BR) split the UK into control areas each area havingncontrol equipment to link it into the trunk telephone network. A fullynequipped control area can handle 40 fixed stations, four telephone trunknjunctions, six direct lines to electric control rooms, one direct linento the train control office, one line to emergency operator and twoninterfaces into the BR teleprinter network. Fixed stations are arrangednin non interfering groups and channel free ALOHAs are sequenced aroundnthese groups. All fixed stations operate on the same control channel butnare allocated a separate traffic channel. The traffic channel allocationnis arranged so that fixed stations can operate without the need fornguarding although the control system can cater for this if futurenexpansion dictates that guarding will be necessary. The ALOHA number isnset at three