Signalling and Signal Boxes

All traffic on a railway was controlled by a system of signals and these were controlled from the signal boxes.

A signal box was usually a two story building with the mechanism for operating the signals on the ground floor and a control room upstairs. In this control room would be the levers to operate the signals for the area of railway controlled from that signal box. The boxes were always located with good visability and extensive windows so that the signalman could see his signals, points, any level crossing that he controlled and the trains themselves of course.

Signalling was traditionally done by semophore signals and these were divided into two types called Home and Distant. These gave the driver of a train instructions depending on what position the coloured cross bar, or signal arm, across the top of the signal post was in.

The Home Signals have arms across the top which are red (indicating danger) on one side and they apply to any trains approaching their red side. These signals were placed close to points, level crossings, stations or any position where a train may be required to halt. If the arm was in the up or horizontal position then this meant danger and the driver of a train was to halt at that position. If the arm was in the down, or all clear, position (a 45 degree down angle) then the train could proceed.

The Distant Signals have arms across the top which are yellow (indicating caution) one side and apply to any trains approaching their yellow side. These signals were placed at a distance before Home Signals and alerted an engine driver that a Home Signal was coming up. If the arm was in the horizontal, or up, position then this meant proceed with caution as the next Home Signal was probably in the up, or danger position, informing the driver to halt his train. This gave trains enough time to come to a halt. If the arm was in the down, or all clear, position (a 45 degree down angle) then the train could proceed normally.

At the end of each signal arm was a lamp with a two coloured lens infront of it and these were used for signalling at night or in bad weather. Both types of signals had a green lens which showed when they were in the down, or all clear, position but when the signals were in the horizontal up position then the Home Signal had a red lens for danger and stop while the Distant Signal had a yellow lens indicating proceed with caution.

Also controlled from the signal box were the points on the railway. These points were trackwork used to switch trains from one line to another. As with the signals they were controlled by the levers in the signal box.

Signal boxes were connected with other signal boxes by a complex system of electric bell codes. When a train passed a signal box the signalman would press a button that rang a bell in the next signal box down the line. This alerted the next signalman that a train was on the way to his section of railway. The first signalman would then send a coded message telling what type of train was approaching by pushing the button several times. For example, three short bell rings would indicate that a passenger train was on the way and different trains had different bell codes. The signalman further down the line would then send a signal back to the first signalman by pushing a button of his own that rang a bell in the first signal box thus acknowledging that the message had been recieved.

Signal boxes could also contain the electric token system when they operated a section of single track railway line. This was a safety feature and it insured that no two trains could be together on the same single track railway line and perhaps collide. A train was only allowed into the section of track if it had a token.

The system used a token which looked like a very large key. At either end of the section of railway line would be an electric token machine, usually within the signal box, and these machines contained the tokens. They were linked electricaly and once a token was removed from one of them another couldn't be removed from either until that token had been replaced in one of the machines.

A train entering the section of single track was given the token at the start of the section and it returned it at the end where it would then be given to a train heading in the opposite direction and about to enter the section or it would be placed in the machine at that end. Once replaced in one of the machines another token could then be removed form either machine.

Sometimes a train wouldn't bother to stop to hand in its token but the train crew would throw it in through an open window of the signal box as they went past to save time. Occasionaly they missed and the token broke the window or rebounded off the wall and fell to the ground. Many times there were frantic searches at night to find a lost token somewhere outside the signal box so that the next train could depart. Either way the signalman had to know when to duck as a large metal token flew towards him from a passing train.

Level Crossings
A level crossing was a point where a road crossed a railway line. For safety they were usually provided with gates that could be closed, either across the road, or across the railway. Usually the road was left open for traffic and the gates closed across the railway but when a train was approaching the gates would be moved to close the road.

The gates were operated either by a crossing keeper (who lived nearby in a purpose built cottage) or from a nearby signal box. When operated from the signal box the gates were opened and closed by a large wheel (looking like a ship's wheel), such as the one in our signal box, and then locked in place by one of the levers.

One of the paintings in the Railway Gallery shows the level crossing and signal box at Sarnau with the gates closed across the railway and the nearby Home Signal in the up or danger position to halt any approaching train.

The Automatic Train System
The Automatic Train System was introduced to improve safety on Britain's railways during the first half of this century. It operated by means of a ramp positioned between railway lines on the approach to a signal. When the locomotive passed over this ramp an electrical contact was made and a bell began ringing in the engine cab alerting the driver to the signal coming up. If this bell was not acknowledged immediately by the driver pressing a button then the brakes were automatically applied. This insured that a train couldn't run away out of control if the engine crew met with an accident and it informed the crew to look out for signals which could, of course, tell them to halt their train.

The Telegraph System
Signal boxes were equiped with the Telegraph during the 19th Century. This item enabled the signal box to communicate with other boxes and stations on the railway by means of morse code. This was a very useful device because other signal boxes could be informed of accidents or delays and could then take appropriate action. For example, if wagons had broken loose and were rolling out of control down the line then the next signal box along could be informed via the telegraph and change points on the line to divert the runaways away from any trains. Trains could also be prevented from entering a section of line where there was a problem by alerting the next signal box. During the 20th Century the telegraph system was replaced by the telephone.