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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.
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.
D-ATC indicator used on the E233 series trains. The digital ATC system uses the track circuits to detect the presence of a train in the section and then transmits digital data from wayside equipment to the train on the track circuit numbers, the number of clear sections (track circuits) to the next train ahead, and the platform that the train will arrive at.
The diagram from Beard's 1897 coupler patent [1]. Janney couplers were first patented in 1873 by Eli H. Janney (U.S. patent 138,405). [2] [3] Andrew Jackson Beard was amongst various inventors that made a multitude of improvements to the knuckle coupler; [1] Beard's patents were U.S. patent 594,059 granted 23 November 1897, which then sold for approximately $50,000, and U.S. patent 624,901 ...
On straight track, the link and pin coupler is used. Since the vertical curve between the straight track sections and the ramp between the lock chambers has a very small radius, the difference in height would be too great for a link and pin coupler, so the locomotives must be pushed through these sections uncoupled by using the side buffers.
The train could then proceed, and a second train could follow. In the earliest days, the second train could proceed after a designated time interval, as on double lines at the time. However, after the Armagh rail disaster of 1889, block working became mandatory. Seeing the train staff provided assurance that there could be no head-on collision.
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.
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.