Semaphore Signals Flashcards
What must you always do with a semaphore signal?
You must always observe a signal, never presume what it will be.
What are the types of semaphore signals?
- Stop
- Distant
- Subsidiary
- Shunt
What does a semaphore stop signal look like?
It has a red background with a white vertical stripe.
What aspects can a semaphore stop signal show?
It is capable of showing a red or green aspect.
What does a white diamond represent on a semaphore signal?
It represents track circuit present.
What does a horizontal semaphore signal indicate?
This is classed as ‘on’ or stop; a red aspect will show at night.
What does a 45° angled semaphore signal indicate?
This indicates that the signal is ‘off’, and the train can proceed.
What does an upright semaphore signal show?
In the upright position, a green aspect is shown.
How may semaphore signals differ in the West Midlands?
In the West Midlands, signals go down 45°.
What does a Semaphore Distant signal look like?
A yellow board with a fishtail end and a black chevron.
What aspects can a Semaphore Distant signal display?
It can display a yellow or green aspect.
What does the horizontal position of a Semaphore Distant signal indicate?
It informs the driver that one of the stop signals ahead is currently on, so they should approach with caution. A yellow aspect would be displayed.
What is the purpose of a Distant signal?
A Distant signal gives a warning about the stop signals ahead; it can only be cleared when the stop signals have been cleared as they are interlocked.
Where is a Distant signal located in relation to the stop signal?
A Distant signal is at Braking Distance from the stop signal in front.
What does a Distant signal at a 45° angle indicate?
It indicates that the stop signals under this signaller’s control are in the off position, allowing you to proceed at normal line speed.
How can a Distant signal be identified?
It can be identified on its plate by an R or a triangle.
What does the rear of a Distant signal look like?
The rear is both white with either a black line or chevron, and there is no aspect showing in the rear.
What should you do if you cannot tell if the signal has cleared correctly?
You must stop immediately and contact the signaller to both report and question.
What are the station limits of a signal box?
Each signal box has its own station limits, from the first stop signal it controls to the last.
What is the typical order of signals in a signal box?
The order typically goes Distant, Home, Section (DHS).
How is signal control typically operated?
This type of signalling is operated in a signal box with wires and pulleys, with interlocked levers.
What is required for a train to clear the block signal?
The train must pass at least 400m into the next block.
How does the distance requirement change with colour light signalling?
This distance is decreased if colour light signalling is used.
What defines a block section in signalling?
A block section is from the last signal controlled by the signal box in the rear to the first stop signal controlled by the signal box in advance.
What does block signalling ensure?
Block signalling ensures that only one train is allowed in one section at one time.
What is an intermediate block signal (IBS)?
An IBS is an additional signal provided at locations with a long block section.
How can an intermediate block signal (IBS) be identified?
The IBS can be identified by a white signal plate with a black line down it.
What controls the intermediate block signal (IBS)?
The IBS is controlled by the signal box in the rear.
What is used to notify the signaller when a train arrives at the IBS?
A track circuit is used on the IBS home signal.
What does the track circuit notify when a train leaves the block section?
It notifies the signaller that the train has safely left the block section and the signals are returned to danger.
What additional signal is related to the intermediate block signal (IBS)?
An intermediate distant signal is also added relating to the IBS.
What can some signals have that can be used as identification?
Some signals have signal plates which can be used as ID.
How do signallers communicate?
Signallers communicate by means of ‘bell codes’ and ‘block instruments.’
How many home signals can you have before the section signal?
You can have up to 4 home signals before the section signal.
What is used before each intermediate block signal (IBS)?
There is a track circuit before each IBS to notify signallers when a train is in that area.
What happens if the block section is too short for the distant signal?
The distant signal B can be combined with section signal A to allow adequate braking distance for a train leaving signal box A.
Who controls the distant signal B when it is combined with section signal A?
The distant signal B is still controlled by signal box B.
What is interlocked to prevent distant signal B from showing an off indication?
The stop and distant signals are interlocked to prevent distant signal B from showing an off indication when section signal A is at danger.
What must the train be able to do if the distant signal is on?
The train must be able to brake for the home signal.
What should you be prepared to do if the home signal clears?
You must still be prepared to stop at the section signal.
When can the distant signal be cleared?
The distant signal can only be cleared when the signaller has first cleared all associated signals.
Can trains on branch lines be held at home signals?
Yes, trains on branch lines can be held at home signals.
When can the signaller clear the branch home signal?
The signaller can clear the branch home signal when the station limits are clear.
What is the position of the subsidiary signal in relation to the main signal?
The subsidiary signal is positioned beneath the main signal.
What information does the subsidiary signal provide?
It provides information on how to proceed.
What colors may the subsidiary signal display in darkness?
It may display red, white, or no light.
What does it mean when the subsidiary signal is cleared and displays the letter ‘S’?
You are permitted to shunt ahead of the signal.
You are permitted to only go as far forward as the move requires.
Where might a subsidiary signal be positioned?
It may be positioned where it is necessary to gain access to a yard or siding.
What does it mean when the subsidiary signal is cleared and displays the letter ‘C’?
You are permitted to proceed but the line ahead may be occupied.
You must proceed cautiously and be able to stop short of any obstruction.
Where can the subsidiary signal displaying ‘C’ typically be found?
It may be found at the entrance to a station.
What can subsidiary signals do in relation to the main aspect?
These can override the main aspect.
What are shunting signals used for?
Shunting signals are used to control movements in sidings or yards and from one running line to another.
What does the shunting signal indicate in the first image?
In the position shown on the 1st image, the signal means stop.
The signal will also show a red light in darkness.
What does the shunting signal indicate in the second image?
In the position of the 2nd image, the signal means ‘proceed at caution as far as the line is clear.’
The signal also shows a green light for hours of darkness.
How are semaphore signals arranged at diverging routes?
At locations of diverging routes, semaphore signals are ‘stepped.’ The highest signal relates to the main route, while lower signals relate to progressive routes to the left or right.
How should stacked shunting signals be read?
When shunting signals are ‘stacked,’ they are read top to bottom, left to right.
What may be found on the same post at some locations?
A distant and stop signal may be on the same post.
Why are distant and stop signals interlocked?
They are interlocked so it is not possible for the distant to clear without the stop clearing.
What do stop signals display?
Stop signals display either green or red.
What do distant light signals display?
Distant light signals display yellow or green.
What indicates that a signal is not in use?
A large ‘X’ is placed on the arm.
What may you find upon approaching a stop signal?
You may find a fixed distant.
What does a shunting signal displaying a yellow aspect indicate?
It applies only to movements in the direction to which the signal can be cleared.
What can other movements do at a shunting signal displaying a yellow aspect?
Other movements can pass the signal without it being cleared.
What may a driver do when a signal is in the stop position?
The driver may pass the signal into the shunt neck or siding and not the running line.
What is a co-acting signal?
An additional aspect may be put on the same pole to act on behalf of a hard-to-see signal.
What is a Fringe Box?
A Fringe Box is where signalling systems transition from Track Circuit to Absolute Block or vice versa.
What is a No Block Line?
A No Block Line is where a signaller does not monitor the condition of the block section.
