Signal (transportation)

“ They direct by signs, which are quite as intelligible as words, the drivers of the trains starting from inside the station, as well as those of the trains arriving from outside. By pulling a lever-handle, a distant signal, perhaps out of sight, is set some hundred yards off, which the approaching driver—reading it quickly as he comes along—at once interprets, and stops or advances as the signal may direct. ”

“ As soon as possible after a fog comes on, a man is stationed at the foot of each distant signal, and generally of each home signal also, who by means of detonators, red and green flags and a hand-lamp, conveys information to the driver of every train as to the position of the semaphore arm. ”

“ Just as the carriage comes to a stop, the engineer or motorman, as we would call him, pulls his lever, thereby fastening the car to the ribbed side of the tube. At once a signal is given and the long, thin but strong rope descends to draw the carriage to the surface.
A perfect system of communication is established from one end of the ponderous tube to the other. It frequently happens when an attempt is made to fasten the car that the clamps fail to work and consequently the carriage commences its second journey toward the center. ”

“ Distant-signals to be distinguished by notches cut out of the ends of the arms, and to be controlled by home or starting signals for the same direction when on the same post. A distant-signal arm must not be placed above a home or starting signal arm on the same post for trains going in the same direction. ”

“ Just consider for a minute the position of an engine-driver with an express train, timed to run at fifty miles an hour without stopping! how many distant signals he has to pass in that distance which he never catches the least glimpse of whatever! and how many times he has to trust to chance, sooner than lose time! ”

“ With a modern interlocking frame, and assuming the normal position of all the signals to be at danger, then before a signal can be lowered for an approaching engine or train all the switches and corresponding signals, from any lines or sidings connecting with the line to be signalled clear must first be set so as to prevent any engine or train coming out of such connecting lines or switches on to the line to be made clear. ”

“ A succession of short blasts means danger ahead—and is used, too, to scare cows and horses off the track.
There is yet another class of signals, which are given with the signal-cord which runs overhead through every passenger-coach. Every one, of course, has seen this cord, and has also seen the conductor use it to signal to the engineer. It is connected with a little valve over the door of the car, and every time the conductor pulls it, there is a little hiss from the valve as of escaping steam. ”

“ The distant signal is placed at varying distances behind the home signal according to the gradient of the line and other circumstances, but on a straight and level railway it would be about 1,000 yards back, and its function is to repeat the action of the home signal, so that if the latter is at danger the driver has timely intimation of the fact, and can at once reduce the speed of his train so as to stop at the home signal. ”

“ Some roads now have the engineman sound a prescribed signal, after the station whistle, to indicate orders to be executed. The objection to this is that valuable time may be lost by the conductor before being sure whether or not he heard the signal. A condition should not be indicated in a negative manner by the failure to do something. All indications should be of a positive nature, that a positive understanding may result and positive action be taken. ”

“ To avoid an accident taking place from the failure of either rodding or gearing, the signal-detector has been devised, so as to prevent the possibility of pulling over the signal wire until the points and locking-bar are both in their proper positions. ”

“ On all railroads there are certain fixed signals for the guidance and information of employees. When caution is called for, the light is usually green and the semaphore horizontal. Now, as the writer looks at it, when any signal indicates caution, it is not to be looked upon as a permissive or conditional signal to be interpreted at will by different enginemen. According to the rules and to common sense when a train, at the time a cautionary signal is sighted, is running thirty or forty miles an hour, it calls for a positive and not a theoretical reduction in speed. ”

“ That is to say, if the despatcher desires to make a meeting point for two trains, he will send the same order simultaneously to both of them. If a train is leaving his end of the division and he desires to make a meeting point with a train coming in, before giving his order to his conductor and engineer, he would telegraph it to a station at which the incoming train was soon to arrive, and from whence the operator would repeat it back word for word, and would give a signal signifying that his red board was turned. ”

“ In fact, the first rule under the “Use of Signals” is that a signal imperfectly displayed, or the absence of a signal from a place where one is usually shown, must be regarded as a stop signal.
The railroads are trying all the time to find some « 77 » third colour which can be used satisfactorily in signalling. Red for danger and green for safety are very well, as far as they go; but a caution signal is badly needed—one which will not absolutely stop a train, but which will warn the engineer to get it under control and proceed carefully. ”

“ If a train, arriving at the signal-box, has to call at the siding, the breakman, or person in charge, intimates the fact to the signalman, who, by the insertion of an ordinary carriage key into the electrical apparatus, disconnects the wire. ”

“ Imagine one of our gigantic locomotives having its opposite drivers electrically insulated from one another!
Figure 18 represents the signal system described in William Bull's English patent of October 31, 1860. In this system, it will be observed, the rail sections used are short, "twenty feet, more or less," and are the terminals of line wires which connect with the battery and magnet at the station. The signal at the station is visual and consists of an indicator operated by wheel work actuated or controlled by the electro-magnet M shown in the diagram. ”

“ The signal and telegraph stations are fifty miles apart, sometimes more. In these long runs the motorman stops only when a signal is turned against him or if by accident he discerns a train in the Tube ahead of him. ”

“ The thin end of a pair of facing points can be jerked far enough open, while a train is passing over at great speed, for the wheels of any carriage to strike them on the reverse side, as soon as the wheels of the previous carriage have travelled about two-thirds the length of the points. Thus it will be seen, that in any of the above-named distances between the wheels upon a vehicle, or between the wheels of one vehicle and those of that following it, if the signals are placed at “danger” before the whole train has passed, the facing points can be jerked open. ”

“ For instance, when a pointsman is letting a train in or out of a siding by hand signal upon the ground, or attending to main line points, during shunting, he is generally upon the spot, and has, of course, the points close under his eye, so that he can at once see whether they are properly closed or not. ”

“ Suppose a train moving along the track, A, A, from left to right in a direction indicated by the arrow. Upon reaching the point, a, the wheels and axles of the train will form an electrical connection between the opposite insulated rails, and a circuit will be formed between the conductor, C, and the conductor, Z, traversing wires, 1 and 2, magnet, M, and wire, 3, and the signal attached to M will consequently be displayed. ”

“ The only things in sight were a water-tank, a pump-house and the telegraph office; and I wish you could have seen that office. It was simply the bed of a box-car, taken off the trucks and set down with one end towards the track. A small platform, two windows, a door, and the signal board perched high on a pole completed the outfit.
I arrived at six-thirty in the morning and there wasn't a living soul in sight. An hour later, a big broad shouldered Irishman who proved to be the pumper, came ambling along on a railroad velocipede. ”

“ The enormous train service on some of these first-rank lines demands the highest efficiency in the signalling and interlocking arrangements, and the use of any devices which will ensure increased facility and safety in the working of the traffic. With a crowd of trains passing a signal-cabin in both directions, and often over four lines of way, it is quite possible for a signalman to make a mistake which cannot be rectified in time to prevent an accident. ”

“ When the electric bell is silent there is no train within half a mile and the crossing is safe; it is not safe while the bell is ringing. As it now stands the law usually provides that the prescribed signals, either bell or whistle, shall be given from the locomotive as it approaches the highway, and at a fixed distance from it. The signal, therefore, is given at a distance of several hundred yards, more or less, from the point of danger. ”

“ Even when a satisfactory form of appliance has been discovered, the manner of using it is by no means simple. It is clearly no use placing such an apparatus im- mediately alongside a stop signal, as the driver would receive the intimation too late for him to be able to stop at the required spot. To place devices of this description at or near every stop signal in a large station or busy junction would involve a multiplication of wires or rods which is undesirable. Every such apparatus should certainly be capable of giving an " all-right " signal as well as a " danger " signal. ”

“ A siding may be a hundred or a hundred and fifty yards from the signal-box. On a dark, and perhaps foggy night, the usual way of performing shunting at the present time is, for the signalman to depend upon the man in charge to show him a white light by hand lamp, or give a signal on a gong worked by electricity, when the main line is all clear for another train to pass. Now the former is a very dangerous system, for where shunting is taking place, the guards and the men in charge have each lights in their hands; there are also lights on the engine, and on the train which is being shunted. ”

“ In more recent years the weight of opinion has been that in all systems of danger signals the normal position, and that to which such signals should automatically move, is that indicating danger. So arranged, the indicator will always be in a position to stop trains unless it is moved to another position to show that there are no orders for them. It becomes a standing order to "hold," and, when an order is forwarded for a train, the fact of its receipt requires that the signal be simply left in its normal position and the train thus stopped. ”

“ There is a code of bell signals drawn up for the guidance of the men, but it will be sufficient to say here that when the train has finished its work at the siding and is ready to go forward, the breakman communicates this by bell signal to the signal-box, and at the same time, by the turning of a button in the front of the instrument at the siding, renews the flow of current, thereby again locking the siding lever and unlocking the signals at the signal-box. ”

“ The signal must be returned to red as soon as a train has passed. It must only be fastened at white when no operator is on duty. This signal must also display red to hold trains running in the same direction the required time apart. Operators must be prepared with other signals to use promptly if the fixed signal « 91 » should fail to work properly. If a signal is not displayed at a night office, trains which have not been previously notified must stop and inquire the cause, and report the facts to the superintendent from the next open telegraph office. ”

“ Moreover, while a train is actually travelling through the points, it is itself master of the situation; not even the signalman can, either intentionally or inadvertently, change their position or disturb them until the whole train is safely passed. When he gives a clear signal for a main line, he cannot open a point crossing to it; when he gives a clear signal for a crossing he must show danger for all the lines which it crosses. And this is the meaning of the numbers marked on the different levers. ”

“ The conductor of the “train,” who is seated by our side, gives the signal for starting by pulling a wire and striking upon the engineer’s bell—far away up the incline and up the vertical shaft, and some distance beyond that again in the engine-house—a certain number of strokes. Instantly we start, and soon are darting up the steep iron way at a terrific rate of speed. ”

“ Special signal installations are sometimes provided away from road junctions to facilitate crossing of the carriageway by pedestrians at points where both vehicular and pedestrian traffic are heavy. The modern types of signals are actuated by vehicle detectors placed in the carriageway and by push buttons or similar devices operated by the pedestrians desiring to cross. ”

“ We will now suppose that the express is yet between B and C, and that another train, approaching in the same direction, whistles to the man at B for leave to go on. This is refused until the C signal-man telegraphs that the line is clear. The same plan is carried out at every signal-box the train has to pass, of whatever nature it may be, whether "express," running at the rate of fifty-five miles an hour, or "goods," steaming along easily at a pace of twenty-five. ”