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Consider a railway with two block sections as in the diagram. Section 1 has frequency A injected at the left-hand end and received at the right-hand end. Section 2 continues from the right hand end of section 1 where frequency B is injected and then received at the right-hand end of section 2. Track circuited railway with two block sections
In any given country, rail traffic generally runs to one side of a double-track line, not always the same side as road traffic. Thus in Belgium, China, France (apart from the classic lines of the former German Alsace and Lorraine), Sweden (apart from Malmö and further south), Switzerland, Italy and Portugal for example, the railways use left-hand running, while the roads use right-hand running.
Double junction, or level junction (left hand running). A double junction is a railway junction where a double-track railway splits into two double track lines. Usually, one line is the main line and carries traffic through the junction at normal speed, while the other track is a branch line that carries traffic through the junction at reduced speed.
The electrical bonding jumper connects the two rails to maintain continuity of the track circuit. Jointed track is made using lengths of rail, usually about 20 m (66 ft) long (in the UK) and 39 or 78 ft (12 or 24 m) long (in North America), bolted together using perforated steel plates known as fishplates (UK) or joint bars (North America).
Absolute block signalling is a British signalling block system designed to ensure the safe operation of a railway by allowing only one train to occupy a defined section of track (block) at a time. [1] Each block section is manually controlled by a signalman, who communicates with the other block sections via telegraph.
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.
In the three-rail configuration, wear and tear of the common rail is greater than with the two other outer rails. In dual gauge lines, turnouts (railroad switches) are more complex than in single-gauge track, and trains must be safely signalled on both of the gauges. Track circuits and mechanical interlocking must also operate on both gauges. [4]
A level junction (or in the United Kingdom a flat crossing) is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front of opposing traffic at grade (i.e. on the level).