Английский язык. Зайцева И.А. - 28 стр.

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SUPPLEMENTARY READING
RAILWAY SWITCHES OR POINTS
The terms “points” and “switches” (the latter is more common in American English) are used to denote
devices, usually comprising tapered metal blades or tongues, for setting alternative routes of running rails. In
the somewhat more general sense of a curved track leading from one track to another, the term “turnout” is also
used in this connection. The most common form of switch is the split switch in which one rail of the main track
and the inner rail of turnout are continuous. There are various other types of railway switches, sometimes
embodying a combination of two split switches (double turnout). Where two tracks simply cross each other
without provision for trains being routed from one track to another, the term “crossing” is usually employed. In
some cases, however, more particularly when the two intersecting tracks form a small angle with each other,
the crossing may take the form of a so-called crossing switch (also known as “slip points”).
The operation of all these devices is similar in principle and can best be explained with reference to
the ordinary split switch. When the straight tongue is in contact with one rail (I) and the curved tongue is not in
contact with another one (II), the switch is set for running straight ahead on the main track. When the switch is
set so as to divert a train coming from the left on to the turnout track, the curved tongue is swung into contact
with the rail II and the curved tongue is now no longer in contact with the rail I. The point of intersection of
the inner rails is called the “frog” of the switch. It is usually in the form of a V-shaped unit. As a safeguard
against derailment the rails opposite the frog are provided with guard rails, and the frog itself is assisted initially
(i.e., at its point) by wing rails to carry the weight of the wheels passing over it.
RAILWAY SIGNAL BOX
MECHANICAL SYSTEM
The switches (points) and signals on a section of railway track are worked by controls accommodated in
a signal box (or tower). On lines carrying scheduled train services these controls are operated in accordance
with predetermined timetables.
In the signal box are pulleys, each connected to an operating lever. When the signalman moves
the lever, the pulley is rotated a certain amount, depending on the desired switch position. A catch secures the
lever in position. A steel wire rope passes round the pulley. The end of this rope is attached to the switch
actuating mechanism or to operating wheel of the main signal. The tensioning device keeps the wire rope
constantly taut. Now when the signalman swings the operating lever, the actuating wheel of the switch
mechanism is rotated through a certain angle by the wire rope, so that the actuating lever (connected to
the wheel) is likewise swung about its pivot and thus shifts the tongues of the switch to the desired position.
The main signal is similarly worked, the arm of the signal being moved by a rod attached to the actuating
wheel.
ELECTRIC SYSTEM
Operating a mechanical signal box involves the exertion of considerable physical force by the signalman.
For this reason in modern installations the points and signals are worked by small electric motors. On a control
desk in the signal box each switch has its own control key (electric switch). Also, there are similar keys for
controlling the signals. The signal box also contains, at eye level, an illuminated diagram showing the track
layout and all the switches, crossings and signals of the section of the railway line. The switch and signal
positions are indicated on this diagram by means of small colour lights. A glance at the panel also shows
whether any particular track is free or occupied by a train. An illuminated diagram of this kind greatly
facilitates the signalman’s task.
A further development, providing even greater convenience and reliability of operation, is the “track
plan” signal box. In this arrangement the signalman’s control desk itself is laid out as a track plan showing all
the signals and switches. Each of these is provided with a key or push-
b
utton by means of which
the corresponding signal or switch on the track can be operated. The tracks themselves are represented on
the control desk by small illuminated compartments. Unoccupied tracks and track sections which at any

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