Part 13 (1/2)

[Illustration: FIG 98--Points open to main line]

[Illustration: FIG 99--Points open to branch line]

It ht that the wheels would buap This is prevented, however, by the bent ends E E (Fig 98), on which the tread of the wheel rests until it has reached so the point of V The safety rails S R keep the outer wheel up against its rail until the V has been passed

POINTS AND SIGNALS IN COMBINATION

Let us suppose that a train is approaching the junction shown in Figs

98 and 99 froh that the driver should know that the tracks are clear He must also be assured that the track, o, is open; and on the other hand, if he were approaching froht, he would want to be certain that no train on the other line was converging on his Danger is avoided and assurance given by interlocking the points and signals

To the left of the junction the ho two semaphore arms on each post These are interlocked with the points in such ato either line can be pulled off only when the points are set to open the way to that line Moreover, before any shi+fting of points can be ence of trains is prevented by interlocking, which renders it inals at ”All right” simultaneously

WORKING OF BLOCK SYSTEM

We nalling trains fronal-box (except, of course, those at termini) has electric communication with the next box in both directions The instruments used vary on different systems, but the principle is the same; so ill concentrate our attention on those most commonly employed on the Great Western Railway

They are:--(1) Two tapper-bell instruments, connected with similar instrus one beat in the corresponding box every tinoletti disc instru with the box in the rear; and the other, in connection with the forward box, having no keys Their respective functions are to give signals and receive the, behind which s”--”Train on line” in white letters on red ground, and ”Line clear” in black letters on a white ground The keyed instrument has a red and a white key When the red key is depressed, ”Train on line” appears at the opening; also in that of a keyless disc at the adjacent signal-box A depression of the white key siives ”Line clear” A piece of ith the ends turned over and passed through two eyes slides over the keys, and can be made to hold either down In addition to these, telephonic and telegraphic instrunalmen to converse

SERIES OF SIGNALLING OPERATIONS

[Illustration: FIG 100--The signaling instruments in three adjacent cabins The featherless arrows show the connection of the instrunal the passage of an express train Signalnalman B's attention by one beat on the tapper-bell B answers by repeating it to show that he is attending A asks, ”Is line clear for passenger express?”--four beats on the bell B, seeing that the line is clear to his clearing point, sends back four beats, and pins down the white key of his instru, and also at that of A's keyless disc A lowers starting signal Trainsection” B pins indicator at ”Train on line,” which also appears on A's instruer B asks C, ”Is line clear?” C repeats the bell code, and pins indicator at ”Line clear,” shown on B's keyless disc also B lowers all signals Train passes B signals to C, ”Train entering section” B signals to A, ”Train out of section,” and releases indicator, which returns to nor at theB signals to C, ”Train on line,” and sets all his signals to danger C pins indicator to ”Train on line” C asks, ”Is line clear?” But there is a train at station D, and signalative The driver, on approaching C's distant, sees it at danger, and slon, stopping at the ho signal D, when the line is clear to his clearing point, signals ”Line clear,” and pins indicator at ”Line clear” C lowers starting signals, and train proceeds C signals to D, ”Train entering section,” and D pins indicator at ”Train on line” C signals to B, ”Train out of section,”

sets indicator at norer And so the process is repeated from station to station Where, however, sections are short, the signalman is advised one section ahead of the approach of a train by an additional signal signifying, ”Fast train approaching” The block indicator renalman of the whereabouts of the train Unless his keyless indicator is at nornals back ”Line clear” to the box behind, a train is not allowed to enter his section In this way a section of line with a full conals is always interposed between any two trains

THE WORKING OF SINGLE LINES

We have dealt with the signalling arrange that a syste into the back of its predecessor Where trains in both directions pass over a single line, not only has this eleer to be dealt with, but also the possibility of a train being allowed to enter a section of line from each end _at the same time_

This is effected in several ways, the essence of each being that the engine-driver shall have in his possession _visible_ evidence of the pernalle line

A SINGLE TRAIN STAFF

The sith of line a ”train staff”--a piece of wood about 14 inches long, bearing the names of the stations at either end This is adopted where only one engine is used for working a section, such as a short branch line In a case like this there is obviously no danger of two trains , and the train staff is merely the authority to the driver to start a journey No telegraphic conals are placed only at the ends of the line

TRAIN STAFF AND TICKET

On long lengths of single line where more than one train has to be considered, the line is divided into blocks in the way already described for double lines, and a staff is assigned to each, the staffs for the various blocks differing fronals are provided at each station, and block telegraph instru that one disc, of the key pattern, is used for trains in both directions On such a line it is, of course, possible that two or more trainsintermediately in the opposite direction

This would be impossible if the staff passed unifored by the introduction of a train staff _ticket_ used in conjunction with the staff

No train is permitted to leave a staff station unless the staff for the section of line to be traversed is at the station; and the driver has the strictest possible instructions that he must _see_ the staff If a second train is required to follow, the staff is _shown_ to the driver, and a train staff ticket handed him as his authority to proceed If, however, the next train over the section will enter from the opposite end, the staff is _handed_ to the driver

To render this system as safe as possible, train staff tickets are of the same colour and shape as the staff for the section to which they apply, and are kept in a special box at the stations, the key being attached to the staff and the lock so arranged that the key cannot be withdrawn unless the box has been locked