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Automatic block signaling (ABS), spelled automatic block signalling or called track circuit block (TCB [1]) in the UK, is a railroad communications system that consists of a series of signals that divide a railway line into a series of sections, called blocks. The system controls the movement of trains between the blocks using automatic signals.
Conventional "trapped key" pin tumbler locks (held in fixed position by solenoids) are mounted in key-release units set up at each end of controlled single line. The number of locks in each unit is determined by the expected traffic frequency; optionally at times short sections may be combined to reduce the number of stops ( see Long section ...
EU Commission funded the project ALARP (A railway automatic track warning system based on distributed personal mobile terminals) in the years 2010–2013 by the total amount of €3,941,877.20. [6] The aim of the project was to improve the safety of track workers through the development of an innovative ATWS using low-cost, rugged, wireless ...
The basic principle is that a track is broken up into a series of sections or "blocks". Only one train may occupy a block at a time, [citation needed] and the blocks are sized to allow a train to stop within them. [1] That ensures that a train always has time to stop before getting dangerously close to another train on the same line.
Under automatic block signalling, signals indicate whether or not a train may enter a block based on automatic train detection indicating whether a block is clear. The signals may also be controlled by a signalman, so that they only provide a proceed indication if the signalman sets the signal accordingly and the block is clear.
A rail break between the insulated rail joint and the track circuit feed wiring would not be detected. Failure modes that result in an incorrect "track clear" signal (known usually in North America as a "false clear") may allow a train to enter an occupied block, creating the risk of a collision. Wheel scale and short trains may also be a problem.
The system is set up by having an axle counter sensor installed at each end of a section. As each train axle passes the axle counter sensor at the start of the section, a counter increments. An axle counter sensor comprises two independent sensors (so the device can detect the direction and speed of a train by the order and time in which the ...
A mechanical lever frame inside the signal box at Knockcroghery in Ireland Waterloo station A signalbox, LSWR (Howden, Boys' Book of Locomotives, 1907). Mechanical railway signalling installations rely on lever frames for their operation to interlock the signals, track locks [1] and points to allow the safe operation of trains in the area the signals control.