This article was originally published in MMTB News July/August 1966 Vol 3 No 6 as The Signal Box Helps Get Them Home, and was written by Driver A.R. Bailey of Glenhuntly Depot. It refers to the operation of the signal box located at St Kilda Junction from 1929 until the redevelopment of St Kilda Junction in the late 1960s.
I wonder how many people, even within the service that is except platform staff pay any attention to the signal boxes that help the flow of traffic, and facilitate the movement of trams across traffic-choked intersections. Like, perhaps, at St Kilda Junction.
Lets see what does happen, taking the St Kilda Road Junction box as an example.
A tram arrives at the junction. The driver brings his vehicle to a halt, sees the points move to make whatever track he is to take, gets the All Clear from the signal lights and the starting signal from his conductor, and moves the tram away. Sounds simple doesnt it? But theres quite a lot behind it all. In simple, non-technical terms, here is what happens.
The equipment used by the signalman to operate the points and signals consists of five machines known as Table Interlockers. These are numbered and labelled as follows:
The interlockers were made for the M&MTB in the United States by the General Railway Signal Company of Rochester, New York, and were installed at the junction early in 1929 by Mr Jack Hicks, who is now Foreman, Light and Power, at Coburg Electrical Distribution Branch.
When the equipment arrived in Melbourne, it was taken to Malvern Depot, where it was tested and assembled ready for use, and then transported to the junction where it was raised up, installed, and connected to the power.
The interlockers are worked with 12 volts DC which also energises the relays that work the signals and points. The signal lights are powered with 110 volts DC connected in series with small lights in the interlockers that correspond with the light indications at the Junction. The globes used in the signal lights are of the 60 watt traction type (as used in all trams). The motors that move the points are operated by 600 volts DC.
Each one of the Table Interlockers is interlocked with the others electrically and mechanically, by means of a system of rods, thus preventing the signalman from making opposing moves. (i.e. sending a tram to ST KILDA BEACH at the same time as giving All Clear to an up tram in High Street.
The machines themselves are a compact unit, and take up little room in the signal box. As mentioned above, each interlockers is fitted with colour lights corresponding with the appropriate signal indication as shown to the tram driver at the junction. The order of light appearances in the interlockers is as follows:
As well as the colour lights there also appears small semaphores or banners in the interlockers with the name of the road set printed on them. (For example, signalling a tram from Wellington Street, to the City, a white light will appear together with a small banner with the words WELLINGTON ST, printed on it, and this returns to blank and the light to Red when the signal is returned to danger.)
To work the signals and points a small lever is provided on each interlocker, and is operated in conjunction with a button which is pressed to obtain the correct signal indication and points setting.
There are three main lever positions on the machines Left, Centre, and Right, marked L, C, R and the levers are moved to correspond with the direction the tram is to travel, so that if a tram arrives at the junction bound for East Brighton or Malvern, the signalman moves the levers on interlockers 1 and 2 both to the left, presses the buttons, and this sets the points for the left curve and gives the Orange light appropriate for that road.
Similarly, if a St Kilda Beach tram arrives, the signalman moves the levers on 1 and 2 to the right, presses the buttons and this sets the points for the right curve and registers the White light, but for down trams to High Street, the No 1 lever is moved to the left and the No 2 lever to the right and the buttons pressed to give the straight line and the Green light.
For an up tram in High Street, one need only move the lever on No 4 machine to the right to obtain the correct signal, and for an up tram in Wellington Street, the lever on No 3 is moved to the right. For an up tram in Fitzroy Street, the No 5 lever is moved to the left and as the points for this line are normally set for the curve there is no need to press the buttons. However, for cross junction movements east and west, it is necessary to press the buttons to change the points.
Although the signal box uses power supplied by the St Kilda substation, power from the SEC can be switched in if there is a power failure. The big spotlights that illuminate the Junction at night are also operated from the signal box.
From casual observation it would seem that a signalmans job is a fairly uncomplicated and easy life. Not so. At peak time there are more than 100 trams an hour through the Junction, and in the afternoon peak the signalman on duty has to keep careful watch of the signals being given to homegoing traffic by the traffic police on duty.
About 1048 trams go through the Junction every weekday, not counting school specials, scrubbers, and other unscheduled cars.
With the reconstruction of the St Kilda Junction soon to begin, and the relocation of the tram tracks onto reserved sections, it will mean the end of the signal box, and with the completion of work, trams will then be signalled through by means of automatic signals actuated by the trams themselves using overhead line contactors such as are already in use in many other parts of the system. So the old will give way to the new, and another phase of development will be completed which will eventually make our transport system the envy of every other city.
I express my thanks to:
Mr R.C. Drummond, Traffic Manager
Mr S. Bramich, Operations Engineer, Coburg
Inspector Bruce Davey
Signalman Leo Allenden
Driver Alan Jungwirth
and many others for their willing help, co-operation and in formation that made the writing of this short article on the operation of signal boxes possible.