Official Guide to the Government Court: N.Z. Centennial Exhibition
Post & Telegraph Department
Post & Telegraph Department
The Post and Telegraph Department has two Courts—one a working Post Office, including money-order and savings-bank, telegraph and telephone. Souvenir home savings-bank boxes, bearing the Centennial emblem, have been specially manufactured and enclosed in neat little cartons with address labels ready for posting. These boxes are on sale at that office. Attached to this Court is a Post and Telegraph philatelic bureau and stamp exhibition, which includes displays of stamps from overseas as well as issues of New Zealand and its dependencies. Dies, plates and rollers used in the preparation and printing of stamps are also exhibited.page 25
The second Court contains interesting working exhibits included in which are:
A Pageant of Progress.
This exhibit depicts by a cavalcade of events the romantic development of the Department during 100 years, the principal events in each five-year period being shown in colourful models and cut-outs in a panoramic setting on a moving escalator with which is synchronised a sound film with commentary, lighting and changing sky effects.
Mechanical air-mail map showing the Empire, Pan American and South African routes. Grouped in front of the map are three binnacles containing press but- tons. On a member of the public operating the buttons, coloured lights indicate the route taken by the air-mail and the approximate number of days taken to fly to each point.
Cook Strait Communication Services:
This exhibit is in the form of a relief map representing part of the North and South Islands in the area surounding Cook Strait. It is arranged to give some indication of the multiplicity of communication services between the two islands, including telegraph and telephone cables and also communication service with ships and aircraft. Arrangements have been made by means of illuminations to indicate the location of submarine telephone cables, and, as each is illuminated, a corresponding descriptive sign is illuminated to indicate the service given by the particular item represented. This applies also to radio stations and to such special facilities as marine radio beacons, which are employed in conjunction with lighthouses as navigational aids to shipping in Cook Strait. Another service represented is that of messages to and from ships in radio communication with the mainland. As with the radio beacon, arrangements have been made to reproduce representative morse signals to give an accurate idea of the way in which the signals are transmitted and received. In connection with the radio beacons, an interesting feature is the manner in which the several beacon stations around Cook Strait transmit in an orderly sequence. The signals emitted from Baring Head, for instance, are followed immediately by those from Cape Campbell. By this arrangement, the navigator of a vessel making use of the radio bearings is enabled to compare one with another without complicated adjustment of his receiving apparatus, and by means of reception from several stations can, if desired, determine his actual position entirely by radio.
A Radio-Telegraph Transmitter:
This is a full-size item of equipment as used in the Department's radio stations for communication with ships at sea, aircraft in flight, and intercommunication with the Pacific Islands.
The Magic Dial:
The purpose of this exhibit is to show the manner in which ultra-short radio waves can be used for communication purposes. A number of electrical devices are arranged on the stand, and in order to control their operation a telephone dial mounted on a small box is employed. This box is entirely disconnected from the other apparatus and may, if desired, be carried about within the confines of the stand. The box is virtually a low-power, ultra-shortwave radio transmitter, and, by transmitting signals in accordance with the number indicated by the dial, a sequence of operations in a receiving set is-established which, in turn, switches on the particular device it is desired to operate.page 26
A Radio-Telephone Channel in Miniature:
Telephone communication between this country and Australia, with extension to other countries, is maintained by means of shortwave radio stations operating on wavelengths between 20 and 40 metres. In addition to the radio transmitters and receivers themselves, there is a complicated arrangement of exchange apparatus and radio aerial systems employed for this service. Some indication of the nature of the latter is given in this exhibit, which is really a model transmitter and receiver connected to miniature aerial systems such as are employed for communication with Australia. Owing to the limitations of space the apparatus has been made to work at a much shorter wavelength—between 2 and 3 metres. The network of wires and receiving and transmitting aerials is necessary in order to obtain directional transmissions and to realise a minimum of interference with telephone conversations.
Looking at Sound:
In telephony and in radio transmission it is necessary to deal with the electrical counterpart of sound waves in air. Sound waves are used to control electric currents which, when required, are again converted into sound energy. The object of this exhibit is to give visual demonstration of the nature of the electric currents corresponding to sounds of different kinds. A number of buttons are arranged whereby pure musical sounds of different pitches may be produced in a loud-speaker and simultaneously observed on the screen of a cathode-ray oscillograph. It will be observed that sounds of different pitches produce different patterns on the oscillograph, illustrating the high and low electrical frequencies of the various portions of the musical scale. To indicate the nature of the electric currents involved when music or speech is transmitted, an additional button provides for passing speech through the-equipment, reproducing it on the loudspeaker, and simultaneously showing it on the-oscillograph. The complicated nature of the speech waves in comparison with the-pure tones is very marked when observed visually.
Teleprinter Exhibit (Working Exhibit):
|(a)||Standard tape transmitters and tape printer: This is the standard machine-used by the Department on circuits linking the larger provincial towns with the main centres. It provides for messages being sent in both directions simultaneously at a speed of six letters per second. The messages to be transmitted are first converted into a series of holes on a tape by means of a keyboard perforator—a machine somewhat like a typewriter—and this tape feeds into a transmitter which causes electrical signals to be sent over the line. At the distant end of the line these electrical signals operate a printer, and cause the letter corresponding to each particular series of electrical signals to be printed on a paper tape.|
|(b)||Page Printer: This machine, as used in New Zealand, is for special point-to-point services, such as between aerodromes and between meteorological offices and aerodromes for weather reports, etc. The depression of a key causes a certain set of electrical signals to be sent to the distant station where the receiving machine prints the letter corresponding to the key depressed. The received message is printed in page form, special signals causing the page to move onwards one line and to move back to the beginning of a line.|
Display of Old-Type Telegraph Apparatus:
This consists of a display of telegraph equipment showing the development in. design from the early days of telegraphy in New Zealand to the present time.
Underground Cable Manhole:
An underground cable manhole with side walls cut away to enable the interior to be seen. Cables, which consist of paper-insulated copper conductors enclosed in a lead sheath, are laid in pipes in the ground, the manhole being the point at which page 27 the cables are led into the pipes and, later, where the different lengths of cable are jointed together. At certain times a cable jointer demonstrates the method of jointing the cable.
An exhibit of the essential parts of a mole drain-plough in action in the laying of a cable.
The blade of the plough supporting the mole to which is attached the cable being drawn in, is shown in section below ground. The use of the mole drain-plough, which is hauled by a tractor, enables cable to be laid much more cheaply and quickly than by manual methods. It is applicable mainly on country roads.
Short samples of various types of telephone cable.
Certain statistical comparisons between cable and aerial line communication requirements.
A number of selected films illustrating certain phases of the Department's activities are shown in the Cinema at intervals.
Historical Display of Telephones:
This exhibit consists of a series of telephone installations showing the improvement in design and appearance of subscribers' telephones from one of the earliest types used in New Zealand to the most modern and efficient types now in use.
The earliest type shown is a Blake Telephone, which was first used in New Zealand in 1877; the latest type is the very efficient handset telephone.
The Small, Private Automatic Exchange:
This exhibit shows the type of equipment supplied for use in large business premises to provide an efficient telephone service for from 20 to approximately 200 telephones. Such an exchange enables a number of telephone extensions to communicate automatically with one another, and to originate and receive calls to and from the public exchange. The installation consists of two units—an attendant's switchboard and an automatic switching unit. The switchboard is for the purpose of extending incoming calls to the required extension. The other unit contains the mechanism to enable the extensions to call one another automatically, or to call any subscriber on the public exchange without the aid of an attendant.
An Inlaid Table.
A table manufactured from 22 New Zealand timbers and made by Mr. J. Williamson who was employed in the Post and Telegraph Workshops for 16 years.