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Tyneside IECC
Heighington and Shildon Signal Boxes
General Method of Operation
Block Instruments

Tyneside IECC

Heighington and Shildon Signal Boxes


These signal box representations have been provided to complete the Bishop Auckland branch which is effectively a dead-end. Trains would otherwise leave Darlington and then return some time later. Instead, a simplified representation of these boxes' lever frames are supplied as well as simple block instrucments. The intention is to provide a basic level of Absolute Block functionality with the emphasis on the IECC side of the simulation so the purists may cry!

There are no train describers for either of these two signalboxes, except a fringe train describer which lets Darlington workstation know what is approaching from Heighington. You should keep track of train identities by any means convenient such as sticky notes or good old fashioned pen and paper.

General Method of Operation


Each lever is shown as an N or R at the top or bottom of each slot respectively. The N indicates the "normal" position, i.e. back in the frame, in its upper position. The background colour of the lever indicates its function - red for signals; black for points.

Each lever can be reversed by right clicking on anywhere in that lever's slot (including the N area). The lever can be restored to normal by left clicking anywhere in the slot (including the R area). If a lever is locked in position by other levers or locking then it will not move.

Some levers are mechanically linked to signals or points so they will change state quicker than, for example, motor worked points or remote colour light signals.

The screen shows the lever number relating to each signal or point - generally signal numbers are shown above or below the signal (except Shildon's 4 and 25 signals), while point numbers are shown between the two ends of the point if double ended, or adjacent to the single end if not.

The two Distant signals either side of Newton Aycliffe are fixed: that is, they always show a caution indication and cannot be changed.

The three repeater signals operate automatically and do not need any user interaction.

As no route locking exists, as a train occupies a track, it will flood the entire track red no matter which way any points lie.

In the lever frame sequences below, each entry consists of a number and a suffix of N or R. For example, 99R means move lever 99 to the reverse position, while 98N means move lever 98 to the normal position.


  • No time locking, such as Welwyn, is provided
  • Sequential clearing of signals is not required and indeed may not be needed (further information would be appreciated)

Block Instruments

One block instrument is provided for each line. The "receiving" box operates the instrument, while the "sending" box has indications as to what the receiving box has selected. In real life the sender would send a bell code asking "is line clear?" at which point the reciever sets his instrument to "Line Clear" (if it really is clear, of course!). The sender can now clear his signals towards the receiver. Once the train enters the section, the sender sends a bell code indicating the train is on its way. The receiver sets his instrument to "Train On Line". When the train arrives at the receiver's box, he can then set the instrument back to "Line Blocked". The sender then sends a bell code back to the sender to indicate the same (train out of section).

In the simulation we don't have the bell codes but the operation of the block instrument is the same. Left click on the large roundel appropriate to the state you wish to set it to.

Note that the "home" signal - H31 or S25 - must be at danger in order to send "Line clear".


The SimSig layout at Heighington is an amalgamation of old and new. The signalling is from around the 1990s but some time in the 2000s it was rationalised slightly (fewer signals), and more recently a new siding to a depot at Heighington was added. At this stage the lever frame was abolished and replaced with a panel.

The levers are shown in descending numerical order due to the orientation of the real life signal box - the signaller's view is of Darlington to the right and Shildon to the left.

The interlocking at Heighington generally behaves as expected. Note that points 30 are locked Normal if a route is set from Darlington, and that points 37 are locked Normal until the slot towards Darlington has been granted.

To accept a train from Darlington and send towards Shildon:

  • (Preconditions 30N, 37N)
  • 38R
  • 36R
  • 35R

As the rear of the train passes each signal, restore that signal to the normal position.

To accept a train from Shildon and send towards Darlington:

  • (Preconditions 38N)
  • Set up the train description in the berth provided (right-click on the four squares and select Interpose)
  • 31R
  • 32R
  • When train arrives at Heighington station, press the "Step Description" circle to transmit the train description to Darlington
  • Request slot by clicking on the hollow green circle
  • When given: 37R
  • 33R

Restore signals as the rear of the train passes each one. Once train is clear of pointwork, normalise lever 37 too.

An Auto Working button is provided which will carry out most of the steps above automatically. It is not foolproof and does not use the block instruments but should help if you don't wish to control the signal box.


The layout to the left of Shildon has changed slightly over the years, swapping the positions of crossovers 4 and 5, and moving signal 25 slightly closer to Heighington. The entry/exit to/from Locomotion is nowadays a ground frame released by Shildon. As the simulation is more about Tyneside IECC than Shildon signal box, this subtle change is not replicated in the simulation.

Only the main sequences of sending a train from Heighington to Bishop Auckland and back are provided here. The other sequences are left for the user's discovery!

To send a train to Bishop Auckland:

  • (Preconditions 5N, 7N, single line and platform at Bishop Auckland clear of trains and locking, 35N)
  • 25R
  • Once train is clear of pointwork:
  • 25N
  • When ready to go to the single line:
  • 24R
  • 27R
  • Once train is on the single line and clear of pointwork:
  • 27N
  • 24N
  • Approaching Bishop Auckland:
  • 29R
  • Once train arrives at Bishop Auckland:
  • 29N

To send a train from Bishop Auckland to Heighington:

  • (Preconditions 7N, 24N, single line clear of trains and locking, 35N)
  • 34R
  • Once train is clear of the platform:
  • 34N
  • Once train is approaching Shildon:
  • 33R
  • 32R
  • 31R
  • Once train arrives in Shildon:
  • 33N
  • When rear of train passes 32:
  • 32N
  • When rear of train passes 31:
  • 31N

An Auto Working button is provided which will carry out the steps above automatically. It is not foolproof and does not use the block instruments but should help if you don't wish to control the signal box. Any irregular moves such as to/from the sidings or the Eastgate line, or terminating and going back to Heighington without going to Bishop Auckland will have to be handled manually.

Tyneside Contents

Last edited by Steamer on 26/05/2019 at 16:45