Absolute block signalling
[citation needed] A train approaching a section is offered by a signalman to his counterpart at the next signal box.[2] This communication traditionally takes place by bell codes and status indications transmitted over a simple telegraph wire circuit between signalmen using a device called a block instrument, although some contemporary block working is operated wirelessly.[4] This was insufficient to prevent a train colliding with the rear of one that had stopped unexpectedly, as happened at the Clayton Tunnel rail crash.[11] Within station limits, the signalman controls the safe movement, and in normal circumstances he can directly see the position of trains there.In July 1837 William Fothergill Cooke installed a demonstration system on the Euston to Camden Town section of Robert Stephenson's London and Birmingham Railway for signalling rope-hauling of carriages (as the locomotives could not cope with the steep incline).[12] Cooke also put forward the idea of dividing a single line into grand divisions of between 15 and 20 miles (24 and 32 km), each subdivided into stages 2 to 5 miles (3.2 to 8.0 km) long that were to be connected together by telegraph, with instruments that showed the state of each stage.The standard British Railways block instrument brought them together in a single small cabinet; its front face displaying two indicators, a commutator handle, a bell and a tapper.The upper indicator shows the state of the forward block – along the line leading away from the signal box.[citation needed] Each bell has its own distinctive sound so that the signalman knows which box is communicating with him.Each communication starts with a single strike of the bell meaning “Call attention”.The recipient signalman then shows that he has received the message by repeating it back to the sender.All subsequent bell messages are acknowledged promptly by repeating back to the sender – with the single exception of six strikes which indicate “Obstruction danger” which is not echoed back until all relevant signals have been set to “Stop”.[18] It is a generalized guide intended to assist signalling staff in prioritizing trains according to their importance as well as ensuring that any special instructions that may apply at a specific location are carried out.
Automatic block signalingsignalling block systemrailwaytrack circuitstelegraphsignalmanbell codesClayton Tunnel rail crashElectrical telegraphcurrent electricityCooke and Wheatstone systemWilliam Fothergill CookeEustonCamden TownRobert StephensonLondon and Birmingham Railwayclearing pointtrain operating companyfreight operating companyEast London LineSaxby and FarmerHeritage railwayRule 55Channel 4Cooke, William FothergillPan BooksRailway signallingBlock systemsCentralized traffic controlCommunications-based train controlDirect traffic controlEuropean Train Control SystemMoving blockRadio Electronic Token BlockTrack Warrant ControlTrain order operationSignalling controlBlock postIntegrated Electronic Control CentreInterlockingLever frameRail operating centreSolid State InterlockingWestlock InterlockingSignalsApplication of railway signalsCab signallingNorth American railroad signalsRailway semaphore signalAxle counterTrack circuitTrack circuit interrupterTreadleTrain protectionAdvanced Civil Speed Enforcement SystemAutomatic train controlAutomatic train operationAutomatic train protectionAutomatic Train Protection (United Kingdom)Automatic train stopAutomatic Warning SystemAutomatische treinbeïnvloedingBaliseCatch pointsChinese Train Control SystemCityflo 650 CBTCContinuous Automatic Warning SystemContrôle de vitesse par balisesEBICABIntegra-SignumInteroperable Communications Based SignalingCrocodileKorean Train Control SystemLinienzugbeeinflussungPositive Train ControlPulse code cab signalingPunktförmige ZugbeeinflussungRS4 CodiciSelTracSistema Controllo Marcia TrenoSlide fenceTrain automatic stopping controllerTrain Protection & Warning SystemTrain stopTrainguard MTTransmission balise-locomotiveTransmission voie-machineLevel crossing signalsCrossbuckWigwagE-signalWayside hornAdtranzAlstomAŽD PrahaFederalGeneral ElectricGriswoldHitachiHyundai RotemMagneticProgress RailSafetranSiemensSmith and YardleyThalesUnion SwitchWestinghouse Brake & SignalWestinghouse Rail SystemsTransport CanadaAustraliaBavariaBelgiumCanadaFinlandFranceGermanyGreeceNetherlandsNew ZealandNorth AmericaNorwayPolandSwedenSwitzerlandThailand