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In the simplest case with three signal boxes on a stretch of line without junctions, the central of the three boxes will receive a request for a train to be accepted, the signaller will set any relevant points (turnouts) and signals and signal acceptance, and then request acceptance by the next signal box along the line.
The signal box provided a dry, climate-controlled space for the complex interlocking mechanics and also the signalman. The raised design of most signal boxes (which gave rise to the term "tower" in North America) also provided the signalman with a good view of the railway under his control. The first use of a signal box was by the London ...
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.
An example is the process of signalling a train in the up direction (from A to C) past a signal box B. The signal box in rear is A and the signal box in advance is C. [2] The block indicators at B are in the Normal position. The signalman at A "offers" the train to B by sending an "Is Line Clear?"
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.
Modern point machines have an electric motor and gears to convert the rotational motion of the motor into the linear motion required to switch the points. The gear assembly also provides the required transmission ratio so that it can generate necessary force to move switch blades. The machine performs the following functions: Moving switch blades.
Box B sends 4 bells to box A. (Acknowledgement, if in the position to accept the train giving permission for box A to signal the train into the block controlled by B.) (when the signalled train enters the portion of line between A and B.) Box A sends 2 bells to box B (Train entering section) as the train passes box A and enters the block ...
Some stop signals are in the form of a fixed signal, generally a white board with a red solid circle. There is usually a panel underneath with instructions to the driver as to what circumstances he may pass the signal. Examples of such signals are used on lines signaled by the radio electronic token block system.