New South Wales Government Railways

by John Hinson

Rockdale signal cabin
Photograph 28/9/67, by Dr J W F Scrimgeour

Rockdale is a suburban station 6½ miles from Sydney on the four-track Illawarra line, with four through platforms and a terminal bay.

The box is of typical large-scale rugged construction of the period from 1910 onwards as power signalling developed. Brick bases were usually employed, owing to the weight of the early power apparatus, and the size of the apparatus often necessitated a deeper box than might be provided for a mechanical frame.

An interesting feature of the architecture here is the bevelled corners of the operating floor windows, although the roof is still squared.

Interior of Rockdale box
Photograph 28/9/67, by Dr J W F Scrimgeour,

A peek inside the box reveals something a little unexpected. This is an electro-mechanical box - the nearby points are worked from the lever frame (of McKenzie & Holland construction) whilst the signals and remote points are controlled by the GRS type "pistol-grip" frame above.

The diagram has all the track circuits indicated on it. Like that at Newcastle, it is "normally lit", meaning that the lamps are extinguished when a section of line is occupied. This less common system meant that the failure of a bulb gave a "right-side" failure, but with the lamps lit for most of the time this often led to scorching of the diagram, as can be seen here.

Diagram at Rockdale box
Photograph 28/9/67, by Dr J W F Scrimgeour,

An additional diagram (without the track circuit indications) was provided at the left-hand end of the frames, and here you can see most of the layout controlled by Rockdale. Interestingly, the power slides and mechanical levers are numbered in the same sequence, leading to a logical numbering system as if all was controlled from one frame.

Notice that the sequence of levers/slides to be operated for every route are listed at the foot of the diagram.

Ritchie Hurn, who was a signalman at Rockdale in 1954/5, visited this site in 2002 and signed the "Train Register".

Comments about this article should be addressed to John Hinson