[Source: Nick Catford]
The signalling system is not the same from Dullingham to Cambridge and Dullingham to Chippenham and the equipment reflects this. Replacing the old block bells is the train describer. That is the screen and keyboard at the far end of the desk, near the window. If Cambridge sends a train the headcode is put in by the panel in Cambridge power box. It shows on the train describer screen, and a warning sounds. When the train reaches a certain point, it illuminates a track circuit (two of the red lights at a time) on the diagram, above the desk.
The signalman at Dullingham can run that train into the loop and into the station by setting the points, the switches with white lights on the box under the diagram. He will clear the relevant signals with the higher switches with the coloured lights. The train will then run into the platform and the signal opposite the box is where it will stop. That train approached under track circuit single line regulations. Now a train is coming from Chippenham Junction. The headcode will be put in at Chippenham and will appear in the train describer. The signalman at Chippenham will press the offer button on the tokenless block equipment which triggers a buzzer, and if the line is clear, the Dullingham signalman will put his switch in the accept position. This is the small grey box with a white indicator dial to the right of the big signalling box on the desk.
When the train passes Chippenham the indicator will show section is occupied and another buzzer sounds. When the train occupies the track circuits on the approach to Dullingham the signalman will close the gates to road traffic, releasing a key from each gate. These are placed in the slots in the grey box at the right of the desk in front of the train describer, and locked in. The train from Chippenham can now be allowed into the platform with the home signal. Once it has arrived with tail light and the signalman has pressed the train arrived button on the tokenless block, he can offer the one waiting to Chippenham, change the points at the end of the loop and clear the signal for that to leave. Cambridge accepts the one waiting on the other platform by unlocking the signal controlling access to the single line and assuming the points have been set and Dullingham operates the section signal, it will be away.
The signalman can now release the gate keys, unlock the gates and put the kettle on. The green box with 2 white lights on top of the tokenless block equipment monitors Woodditton crossing. It shows that the crossing is operating and if it is down too long it alarms and shows the failure, or if the barriers go down at the wrong time, i.e.fail, it shows that. White lights show all is well, and red lights show the barriers in other than the up position. The switches cancel the alarm sound, one for each side. All functions of locking and release of the gate lock keys are performed on the silver box at the right end of the desk. The box at the left of the desk is the phone console, all signal phones crossing phones and circuit phones were worked from there. The white phone on top is a nearly modern phone that can connect to the rest of the world. The blue tube on the windowsill is where the detonators were kept after health and safety took over. They used to be just laying on the window sill.