THE SIGNAL BOX

OVERSEAS

MIDLAND JUNCTION "B"
Western Australia Government Railways

by John Hinson

Midland Junction 'B' cabin
Photograph from the collection of Dr J W F Scrimgeour, 1969

Apart from the locomotive, there is little in this view that was not manufactured by McKenzie & Holland. The all-timber cabin and the somersault signals with revolving discs are all from their workshops and are of typical design. Notice how the signal on the right has been modified after insects have eaten away at the base.

Interior of Midland Junction "B"
Photograph from the collection of Dr J W F Scrimgeour, 1969

This view shows the McKenzie & Holland lever frame, together with the signalling instruments and the layout diagram.

The block instrument on the left is of considerable interest, being of the Dowson's three-position type. Harold Dowson was the Signal Engineer of the WAGR from 1898 to 1926, and later worked for the Bombay, Baroda & Central India Railway. He invented this instrument as an improvement on Winter's blocks, having three indications and extra security in the provision of a treadle release to confirm that trains have left the section. They were manufactured in the WAGR workshops.

Dowson's block instrument at Midland Junction 'B'
Photograph from the collection of Dr J W F Scrimgeour, 2/69

The Dowson's three-position block instrument controlled the double-line section between Midland Junction "B" and Bellvue.

Sketch of Dowson's blockThe left dial was the red needle, used for trains approaching the box. The right dial had a black needle and applied to departing trains. The Black Button was used in conjunction with the Red Switch, whilst the Red Button and the White Button were used for cancelling and for clearing in the event of treadle failure. The Red Switch was normally free, but became locked when at ON LINE and remained so until the arrival of the train was detected by a treadle release.

Operation was as follows:

At the time these pictures were taken, this section was the last to be signalled with Dowson's blocks. They are now long-gone, in fact there is not even any nechanical signalling now remaining in Western Australia.


Comments about this article should be addressed to John Hinson