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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.
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 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.
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 link-and-pin coupler consisted of a tube-like body that received an oblong link. During coupling, a rail worker had to stand between the cars as they came together and guide the link into the coupler pocket. Once the cars were joined, the employee inserted a pin into a hole a few inches from the end of the tube to hold the link in place.
Railway interlocking is of British origin, where numerous patents were granted. In June 1856, John Saxby received the first patent for interlocking switches and signals. [2] [3]: 23–24 In 1868, Saxby (of Saxby & Farmer) [4] was awarded a patent for what is known today in North America as “preliminary latch locking”.
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To clip and scotch a set of railway points (Amer. a switch) uses two pieces of equipment to temporarily lock a set of points into a particular position. [1] The point clip clamps the end of a moving rail (the switch rail ) of a set of points to its associated stock rail , and the scotch is a timber wedge used to ensure that the other moving ...