Signalling and Interlocking.

Probably no branch of engineering has developed more rapidly and been subject to more changes than signalling during the past 15 years. The development from the older type of mechanically operated signals and points, with which most people are familiar, to the latest development of centralised traffic control, by means of which points and signals are operated from a central point over lengths of line of 50 miles and more, is a very great advance. These developments have been possible only through the perfecting of signal apparatus and the adoption of many of the most ingenious inventions. Modern signal apparatus is complicated, but it can, when properly installed, do almost anything except think.

As is generally conceded, signals provide for the safety of traffic, but in addition to this, signals assist in the expeditious control of traffic. This latter function is not always quite so clearly appreciated.

The New Zealand Railways have followed the development of signalling fairly closely and, although at the present time there are no installations of centralised traffic control, automatic signalling has been installed over 318 miles of the railway. In addition to this, there are 107 mechanical interlockings for operating yards, and 27 interlockings operated by electric or pneumatic power. All facing points on the Main Line between Auckland and Invercargill not controlled by complete interlocking are key locked, and detected in such a way that the safety of the Main Line is assured.

To most people signalling only means a series of posts by the side of the railway, at any one of which a train stops when the signal is at “danger.” There is little realization of the complicated control and apparatus—usually out of sight—by means of which the indications of the signals are controlled to ensure reliable working, to continually safeguard the passage of trains, and in all weathers and at all times to give the necessary indications and assurance to the engine-driver that he can safely maintain the speed of his train, knowing that his road is safe.

Supplementing the signals, the tablet system, which has been installed throughout the Main Lines and on the major Branches, gives assurance to the driver that his section is clear for the passage of his train.

A description of the possibilities of signalling in expediting traffic would require too much space to be dealt with here, but there is one phase of the question which may be touched upon, and that is, that it is only by close co-operation and by making the fullest use of the facilities afforded by signalling that the best results can be obtained in traffic working.

In order that the best and most flexible schemes may be devised, it is necessary that the very fullest information should always be available in regard to the traffic operations which the signalling is required to control.

It is sometimes stated that signalling costs a good deal of money, and this is true to the extent that reliable apparatus cannot be cheap; but the decision as to whether anything is expensive or cheap must be measured by results.

The results of signalling are safety and efficiency in traffic operation — both almost impossible to calculate in pounds, shillings and pence, but nevertheless real; and railways throughout the world, even in these financially difficult times, are still installing signalling, particularly of the automatic type, and to quote a leading English authority upon economic working, “Signals mean Salvation.”

Communications.

The recent activities of the Branch have been very largely concerned with improvements in the communication systems of the Railway by telephone and telegraph operation.

During a number of years, additional points of communication have been required and these were added from time to time to the existing lines, nearly all of which were of the old iron wire type. In the days that these were installed, this was the general practice, but later requirements have demanded line improvements page 13 to take advantage of the modern developments in communications. It is hardly necessary to emphasize how great these improvements have been. The recent introduction of radio to almost every home for instruction or entertainment during the evenings, is one striking instance.

Possibly the most useful among later inventions for communication systems is the Fleming valve and its allied developments.

Electro-Pneumatic Signalling In New Zealand.
(Photographic study by W. W. Stewart.)
The A Signal-box at Auckland (128 levers) controlling traffic operations over 1 1/2 miles of track.

Another development in reorganising the communication services of the railways is the use of one pair of wires to carry more than one circuit. By this means, superimposed over telephone wires, morse can be operated, and so two channels of communication can be given where only one was the usual practice in the past. Further developments of this system may be used in the future, by introducing the carrier current system, by means of which it is possible to have a large number of telephone conversations travelling at the same time over the same pair of wires.

The general scheme for the installation of selective telephones for train control purposes, approved by the Management some two years ago, is now nearing completion. Some sections are completed and in use, and with the completion of the major scheme this year, many additional facilities will be provided for the efficient operation of trains.

The importance of communications needs no emphasis, as it is by these alone that co-operation in the working of traffic can be efficiently carried out.

Electrical.

The provision of electric lighting has become almost a necessity in these days, and the Department has recognised this by the fact that it has completed only last year a programme for the provision of electric lighting at the majority of stations. There have been installed a total of 39,185 lighting points and 2,401 heating points. Then there is the provision of power for the driving of machinery and tools, and the Signal and Electrical Branch has been responsible for the design and installation of electrical plant for the Railway Workshops, numbering among them four of the largest industrial works in the country.

Electrical drive for smaller workshops and running sheds has also been installed, with many minor installations throughout page 14 the system for pumping, cooking and other purposes.

The extent to which electrical power is used by the Department is indicated by the size of the total installed load, which is equivalent to approximately 18,000 B.H.P. at the present time. When it is considered that practically all this development has taken place during the past ten years, it will be realised that the Department has taken full advantage of the facilities afforded by the development of electrical power in New Zealand.

In these days it is hardly necessary to point out the cleanliness of operation by means of electric power, the convenience with which that power may be switched on and off as required, and the quietness of operation compared with the older forms of mechanical drive, and the many other advantages which do not need to be stated as they are obvious to everyone living in New Zealand where electrical power is so generally used.

Electric Traction.

The design, installation and maintenance of electric traction is also under the supervision of the Signal and Electrical Branch. Up to the present the New Zealand Railways have not yet any long sections of line operated by electric traction, but this method of operation is one

In The Snow-Capped Mountains Of Switzerland.
Basle-Milan through Express, St. Gothard Railway.

which is now engaging the attention of most railways throughout the world. Many very large installations have been carried out and there is no question that, without going so far as to say that the Railways should be electrified en bloc, there is a number of places where the adoption of electric traction presents many advantages and economies. The cleanliness and general convenience to passengers needs no emphasis to any that have traversed the Lyttelton Tunnel under steam and electric traction conditions.

It will be appreciated that in a brief article of this description only outlines can be given, but sufficient has been said to indicate upon broad lines the functions of the Signal and Electrical Branch and its place in the operation of a modern railway system.

Electrical facilities will, in the future, be made use of even more than at present, and for many purposes not contemplated at the present time. The Management's appreciation of the value of electrical development, as indicated in the foregoing brief summary, would indicate that the New Zealand Government Railways will not be behind in taking fullest advantage of any increased facilities offered by new developments in the application of electricity in the future.