Tag name:Railway


10th April 2020

General Notes

The simulation is based on how the Romsey Signal Box was operated just before its closure in 1982. The simulation therefore uses BR standard bell codes and allows passenger services to use the eastern crossover points as these were electrically operated and locked.

Control of the Simulation

The larger you can make the browser window for the simulation the better. While I have attempted to make the simulation responsive to the size of its window, my main testing was done on a 1920x1280 display. On my tablet it looks reasonable and can be used. On my mobile phone it will display but it is very hard to use - particularly if the phone is in portrait mode!

To move a lever you can simply click on it. If the lever is unlocked it will move to its other position. If a lever is locked hovering of it (for those using a mouse) will display text indicating why the simulation has locked the lever.

To make a bell push simply click the large button. A gap between pushes of a second or less will be treated as a short gap, a long gap is up to two seconds. The remote boxes use a cadence of one second for a short gap and 1.5 seconds for a long gap.

To move the commutator between Normal and Line Clear or Train On Line click on the buttons (the greyish squares) next to the desired position of the commutator control.

If you want to see what the simulation thinks the remote box is doing, you can hover (again for those using a mouse) over the image of the remote box's bell to see what it is up to

To add a train or a complete schedule of trains to the simulation, choose the train or schedule from the pull down in the bottom right of the simulation. Once the Add button is pressed the selected train or schedule will be added to the simulation. The complexity of the task roughly increases from the top to the bottom of the entries on this pull down.

The simulation can be speeded up using the speed controls. This only affects the speed of the trains themselves, the timing of the bell code ringing will be unaffected by the simulation speed.

For those new to signalling

In absolute block working, a block section (or simply section) is a section of railway line between one signalbox and another – in absolute block, lines are paired, with an up and a down line which run in opposite directions.

The block instrument consists of a small cabinet; its front face displays two indicators — telegraph needles — and has a commutator handle (some early designs of block instruments had miniature semaphore arms instead of needles). The upper indicator shows the state of the forward section, on the line leading away from the signal box. The commutator is used by the signalman to indicate the state of the section approaching his signal box, and the lower indicator repeats the commutator position. All indications are repeated on a similar instrument at the other end of the block section, in the associated signal box. The commutator has three positions and each of the two indicators has three positions: normal (or line blocked), line clear, and train on line. Either integral to the instrument or separately mounted, there is a single-stroke bell and a bell operating device, either a tapper or a plunger.

In a simple double line configuration where the signal boxes are A, B and C in succession, the signal box at B will have two block instruments, one for trains in down and up direction in the section between AB (trains leaving station B and trains approaching station B), upper and middle part of the first instrument and one for trains in up and down direction in the section between BC (trains leaving station B and trains approaching station B) upper and middle part of the second instrument.

The signalling bell, also known as a block bell, is used in conjunction with the block instruments if the bell is not integrated with them. It is a single stroke design and relays the codes from adjacent signal boxes. Each bell has its own distinctive sound to alert the signalman which instrument needs to be attended to.

Example block-bell exchange

Box Sends Meaning
A 1 Calling Attention
B 1 Attending
A 3-1 Is line clear for a Class 2 train?
B 3-1 Line is clear for a Class 2 train

An example is the process of signalling a train in the up direction (from A to C) past a signal box B. The signal box in rear is A and the signal box in advance is C. The block indicators at B are in the Normal position. The signalman at A "offers" the train to B by sending an "Is Line Clear?" code on the block bell; for example to offer an express passenger train, he sends four beats consecutively; an ordinary passenger train is offered by sending three beats, and after a pause one more beat, usually written as 3-1. If the signalman at B can accept the train safely (if there is no other train in the section, and the line is clear up to B's clearing point[3]) he "accepts" the train by repeating the bell signal, and placing the commutator on his block instrument for the section from A to "Line Clear". The "Line Clear" is repeated at box A, and allows the signalman at A to clear, or "pull off", his signals. In case the line is not clear, B simply does not acknowledge A's "Is Line Clear?", and leaves the commutator in the Normal position.

At this point, B will not clear any of his signals. Firstly, he cannot clear his starting signal without a "Line Clear" from C. As a result, B will not clear his home signal – he can only clear it when he either has a clear run through (which he does not have without a "Line Clear" from C), or is confident that the train will be able to stop at his starting (or section) signal (this is not done until the train is in view and visibly under control). Finally, his distant will not clear without both his home and starting signals being clear.

Box Sends Meaning
A 2 Train Entering Section
B 2 I acknowledge your train entering section

As the train passes the starting signal at A, the signalman there sends the "Train Entering Section" signal (2 beats) on the block bell to B, and the signalman at B acknowledges the signal and moves the commutator to "Train On Line". His lower indicator on the block indicator to A repeats the position of the commutator.

B immediately offers the train on to C, after calling for attention, by sending the "Is Line Clear?" bell signal (repeating the same steps A had done while offering the train to B); if C accepts it he repeats the bell signal and places his block indicator to "Line Clear", which moves the position of the upper needle indicator in B's block instrument to repeat that indication. B may now clear his signals for the train.

Box Sends Meaning
B 1 Calling Attention
A 1 Attending
B 2-1 The train has now cleared the secion
A 2-1 I acknowledge that the train has cleared the section

After an interval, the train will arrive and pass B; as it does so, B sends "Train Entering Section" on the block bell to C. Then C acknowledges the bell signal and places the block instrument to "Train On Line". As the train passes, he restores his signals to danger, and when the whole of the train passes B complete with tail lamp attached, B sends the "Train Out Of Section" bell signal (2-1) to A and when A acknowledges it, he places his block indicator to "Normal". The block section between A and B is now normal and A can offer B another train, if he has one.

When the train has reached C, the signalman there sends "Train Out Of Section" on the block bell and when B acknowledges it, C places the block indicator to "Normal".

Direction Lever

As the line between Romsey and Eastleigh was singled in 1972, a direction lever is used to control the single line. There is a direction lever in both the Romsey and Eastleigh signal boxes. When a train needs to be signalled through the single line, block bells are used in the same manner as for a double line. However rather than a block indicator being used, the direction lever is used instead. To indicate that a line is clear for a train, the direction lever at the far end of the line is pulled to make that indication. The signal protecting the entry to the single line cannot be pulled (to indicate to the train that it can proceed) unless the direction lever at that far end has been pulled. Once the far end has acknowledged that the train has entered the section, the direction lever is replaced to its normal position.

Text on absolute block signalling taken from Wikipedia and used under terms of the Creative Commons Attribution-ShareAlike 3.0 Unported License. The text used on this page was added to Wikipedia by Wikipedia users (and IP addresses) JonRoma, Denelson83, Afterbrunel, Signalhead,, Danny252,,, Just a guy from the KP, Sir Ross BA, BD2412,,, Hairy Dude, and

Romsey Signal Box Simulation Plugin Details

10th April 2020


This plugin adds support for my simulation of the preserved Romsey Signal Box by:
  • adding a shortcode, romseySignalBox, to add the simulation. Examples of use: [romseySignalBox]Text that will appear at the bottom middle of the simulation. Typically this would display instructions or hints.[/romseySignalBox]
  • Also, as is standard for my plugins, it adds a shortcode to add the current version number of the plugin: [romseySignalBoxVersion]
  • Version: 3.161.0
  • Author: David Vines
  • Last Updated: 2021-09-09T14:09:19Z
  • Requires WordPress Version: 4.0 or higher
  • Tested up to: 6.0
  • License: Uses sounds by Alexander available from Orange Free Sounds used under the "Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)" license and the segment display by Rüdiger Appel available from 3quarks used under the "Attribution 3.0 Unported (CC BY 3.0)" License. Javascript (other than that for the segment display) and php code in the plugin may used under the 3 Clause BSD license.

Change Log


Currently none, but possible enhancements include:

  • Add the missing repeater instruments
  • Align the repeater instruments with their corresponding lever
  • Allow the commutator control to be turned as well/instead of the buttons
  • Addition of the lights for the automatic half barriers at Halterworth
  • Addition of (a much simpler) simulation of the Halterworth crossing box before its automation
  • Addition of a tutorial mode
  • Correctly handle shunt movements
  • Get Eastleigh to honour the direction lever
  • Possibly add a 1909 variant (either just the timetable (most likely) or its map as well)
  • Add (fake) position lights for the sidings and add some train movements for those too

3.161.0 - 09 September 2021

Fix update detection logic

3.157.0 - 21 July 2021

Common up wordpress plugin updating logic with my other plugins

Fix updating logic!

3.153.0 - 21 July 2021

3.108.0 - 29 March 2021

Update URL of the details page

3.101.0 - 13 March 2021

  • Fix estimated time to leave section when something happpens between parts of the traversal of the section.

3.100.0 - 01 March 2021

  • Add a timetable for 19 Feb 2021 when there were major engineering works in southampton so the GWR services were diverted via Eastleigh and the SWR service terminated at Romsey (and used line to Eastleigh to change platforms), all while the freight services are also diverted via Eastleigh and an Engineering Train from Southampton needs to return to base.

3.99.0 - 01 March 2021

  • Refactor code of how change of destination works fixing some minor bugs in the process

3.76.0 - 28 January 2021

  • Add support for self-hosted update notification

3.64.0 - 29 May 2020

  • Adjustment to the overlaps for the platforms. Adjusted the train's movement on the up line to extend the track circuit for C to include the track between the platform and the points controlled by lever 8

3.63.0 - 28 May 2020

  • Only one pull on levers 3 and 13 is permitted after the line is cleared by the relevant remote box

3.62.0 - 24 May 2020

  • Track circuits now overlap (based on the actual overlaps recorded on the 1973 track plan). There still some tweaking to do here, particularly for the artificial track circuits for the platforms
  • Improved train timings. Again based on the 1973 track plan. The current trains use modern train speeds (i.e. 80 mph for the passenger trains)
  • Commutator locked up to the signal box

3.56.0 - 02 May 2020

Many changes including:

  • Additionally lock levers based on the track circuits occupied
  • Reduce the time gap between Train Entering Section and the next track circuit being occupied
  • Revised how the timetable and active trains are shown
  • Have the remote boxes complain if things are out of sequence (including a missing Train out of section, or a commutator is not reset)
  • Trains now verify points are as expected by the train (and the driver will complain if mis-set
  • Train driver will call if they are held at a signal for over a minute
  • Adding multiple trains will add the trains with different train codes (up to ten, then numbers will cycle)
  • Train drivers will check the next track circuit is unoccupied before entering the next section (note: this should only occur if signals are not replaced by the signaller after trains pass them)
  • Remote boxes will wait five seconds before offering a new train once a train leaves the section
  • Remote boxes will ignore offers while the line is occupied
  • The code that recognises bell pushes has been overhauled. Long pauses are now only recognised if it is where a long pauses could be and if it is at least quarter of a second longer than the average for the other pauses

3.50.0 - 11 April 2020

Minor adjustments to train timings. Minor refactoring of how the remote boxes handle bell pushes when they expecting a train entering section bell code.

3.49.0 - 10 April 2020

Initial Version

The information on this page was retrieved by Plugin Information Version 3.202.0.

Romsey Signal Box Simulation

5th April 2020

Up Line

Down Line


Down Line

Up Line





Down Main Outer Home & Distant
Down Main Inner Home
Down Main Starting
Down Branch Distant
Down Branch Home
Direction Lever From Eastleigh
Down Main Points
Up Branch Points
FPL on No. 8
Cross over Points East
Up Main Points
Up Siding No. 1 Points
Up Branch Starting
Up Siding No. 2 Points Release
Cross-over Points West Release
Up Branch Inner Home (Platform Starting)
Up Main Advance Starting
Up Main Inner Home (Platform Starting)
Down Main Draw Ahead
Up Main Outer Home & Distant
From Up Main Shunt
From Down Main Shunt
From Up Siding No. 1 Shunt
Time Box Bell Code
This is a simulation of the levers and other controls inside the preserved Romsey signal box. Note that this is much easier to operate than the real thing since the map diagram is dynamic and shows current point and signal settings on the map. More details on the operation and implementation of the simulation are available. This is Romsey Signal Box Simulation Version 3.161.0
Train Origin Destination Location Status


  • From: Kimbridge Box

This is Kimbridge Signaller. I have yet to receive a Train Out of Section for 1S27. Is there a problem?

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