Dduallt Up Home Signal

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Dduallt Signalling - circa 1970

When the initial phase of signalling the FR, circa 1970, took place, Dduallt was a terminus station with two northward non-passenger extensions – the original formation towards the old Moelwyn tunnel and the deviation which was slowly being extended. Passenger services to Dduallt had been started in 1968 with a run-round loop, the entry facing points with an FPL (facing point lock) and electric staff for the single line between Tanybwlch and Dduallt. See Yellow Signalling Opening Notices for the Signal Opening Notice, 71/4 dated 31st. May 1971.

Dduallt had no power supply, thus the signalling had to be purely mechanical, and the station was normally unmanned with the ground frame being worked by the traincrew. The signalling provided was an Up Home Signal, splitting running shunts at the facing points and a Limit of Shunt (LOS) to allow engines to run round their train with a train in-section to Tanybwlch. A second ground frame was provided at the top end and the points fitted with an FPL.

The tallest available signal post was used for the Home signal, but due to the curvature of the line and the rising mountainside a mechanical banner was provided to give adequate sighting for heavy passenger trains on the upgrade. The Home signal was upper quadrant, whilst its banner repeater was lower quadrant. Not ideal but that was what was available.

The ground frame levers were:

1 Facing Points

2 FPL (facing point lock)

3 Up Shunts

4 Up Home


A hinged sign was provided at the ground frame, similar in design to the changeover signal U-signs at the intermediate passing Loops, with the indications:


‘S’ in black on a white background: Signalman on duty; trainmen must not operate the Ground Frame unless authorised to do so by the Signalman.

Unlettered black board: No Signalman on duty; if the trainmen have the Electric Train Staff in their possession, they may operate the Ground Frame themselves. If they do not have the Train Staff, trainmen must telephone Control for instructions.


The Up Shunts were a pair and, as at Harbour, were worked from one lever with a point detector selecting which disc would come OFF when the lever was reversed. The upper disc led to the Main, left hand, line, and the lower disc for the turnout, which led to the siding which was used for engine run rounds and thence to other sidings used by the Deviationists and the PW.

Space was restricted for the shunt signals. The signals had to be on the left hand side of the line in order for the driver of a double engine, running round a train, to see them, as for much of the operating season the fireman worked the ground frame. The other sighting issue was that the shunt signals were running shunts, that is, they needed to be observed, and obeyed, by UP trains running into the station. Initially the shunt signals were on the wall of Rhoslyn cutting, about six feet above rail level. However, the sighting of these running shunts was still poor for UP trains, so they were then mounted higher on a platform supported by an ex-LSWR short lattice post. The commissioning of the signalling at Dduallt was done in stages as each bit was got ready:


By 1st. May 1971 4-lever ground frame installed and working


31st. May 1971 Up Home & Down Limit of Shunt brought into use


Soon after Up Caution Board installed (made in Boston Lodge – carriage work caused the delay)


By 24th. September 1971 Banner Repeater working


By 22nd. May 1972 Double discs installed but not connected


19th.August 1972 Double discs brought into use


Late 1972 Double discs mounted on a lattice post


Early 1973 Top ground frame brought into use.


The following drawings in the S&T reference folder 1969 illustrate what was installed at Dduallt:


SG-4a Upper quadrant semaphore

SG-4b SR shunt target

SG-13 Schematic mechanical point detection

SG-23b Stevens ‘knee’ ground frame

SG-63 SR shunt signal