INVISIBLE SERVANTS

Wairarapa Times-Age, 28 November 1939, Page 6

INVISIBLE SERVANTS

POST AND TELEGRAPH EXHIBIT. HOME USE FOR RADIO. One of the most fascinating exhibits in the Government Court at the Centennial Exhibition is the radio section of the Post and Telegraph Department’s display, which includes several modern wonders of science adaptable for domestic use. This section includes devices by which a bell may be rung merely by waving the hand; a telephone dial, which will set all sorts of domestic electrical appliances in operation, by the twirl of a finger; and a machine which enables visitors to look at the sound of their own voices on a screen. The magic dial, as it is called, demonstrates the use of ultra-short radio waves for communication purposes; a radio set, electric lights, and other apparatus may be set in operation by the dialling of their particular number. The telephone dial, which is mounted on a small box, may be carried around within the borders of the stand, and in the home it could be used in any part of the house for turning on an electric stove, water jug, radio or toaster. The fascinating possibilities of the magic dial are impressed on visitors, who leave the stand with rosy visions of setting their coffee-pots and toasters and wirelesses in operation in the morning by dialling from their beds without having to go to the kitchen. The box, with its magic dial, is an ultra-short wave radio transmitter, which transmits signals in accordance with the number indicated by the dial. These signals are picked up bj’ receiving sets, which, in turn, switch on the particular device. LOOKING AT SOUND. A device, which is revealing new possibilities as astounded visitors show their enthusiasm at seeing their voices on a screen, is the machine which demonstrates how the counterpart of sound waves in air may be dealt with for radio transmission and telephony. This exhibit gives a visual demonstration of the nature of electric currents corresponding to sounds of different kinds. A number of buttons producing different pitches of pure musical sound are arranged so that, as any of the buttons is pressed, its sound is recorded on the screen of a cathode ray oscillograph. Sounds of different pitch produce different patterns on the screen of the oscillograph, illustrating the high and lew electrical frequencies of the varying notes of the musical scale. Normal speaking tones may also be shown on the screen, and it has been found that the sounding of pure vowels in speaking produce more distinct patterns than those produced by slovenly speech. On many occasions visitors have sung into the mouthpiece of the instrument, transmitting the waves to the screen, andtvaluable visible proof of the purity of their notes and enunciation is given simultaneously. A tall ehromium-plated standard is the form taken by the invisible bell push. By waving a hand a few inches in front of it. it is possible to ring a bell in a distant part of the exhibit. This, again, is an intriguing example of how a development in the science of radio may bring magic to the homes of the people. It is easy to imagine how effective it would be just to wave a hand and a few moments later have a servant appear at the door. The Post and Telegraph Department is making magic an everyday business.