SEEING BY WIRELESS.

Hokitika Guardian, 5 February 1924, Page 1

SEEING BY WIRELESS.

ll is well known that pictures can he reproduced at a distance by special wireless instruments, hut it inis remained for a clever young inventor, Mr J. L. Baird, to show how persons, view-, and even moving scenes can he instantaneously visualised by similar means. How this is done is difficult to explain without diagram.,, but it is hoped that readers a ill lie able to get some idea of the apparatus used from tlie following description. Some dimensions which have been adopted for the first model are given to make the explanation more easily understood. At the sending station the scene to ho transmitted is focussed by a lens on the surface of a rotating disc, which is perforated with a series of holes arranged in one spiral turn. The disc is 20 inches across, and the image, which measures 2 inches square, is close to the rim. As the disc revolves each hole passes a narrow strip of the image, the first hole of the spiral passing the outermost strip, and the last covering the innermost one. Light from the scene shines through the holes on to a substance behind the disc, which changes its electrical resistance instantaneously and proportionately with the variations in the intensity of tile tight thrown upon. it. If, therefore, this substance is placed in an electric circuit- we shall got variations in the current corresponding with the lights and shades of the strips. This varying current, after being amplified, is transmitted to the- receiving station. Here the strips are represented bv nit equal number ot vertical rows of minute electric lamps, which are mounted in a. picture frame. The received currents are led to the fulcrum of an arm. with a copper brush at the end. which rotates round a ring ol tiny contacts, each of which is connected to one lamp. The J' sc at the sending end, and the arm at the receiving end, are synchronised to rotate in unison, hence while each hole in the disc is passing its strip of the image the brush on the arm i- sweeping over the contacts lor the corresponding row of lamps. Since tile disc and arm rotate at twenty revolutions a second, the complete image is tepmduced in the varying brightness ol the lamps at this rate, which is fast enough to avoid flickering. Lamps of only one-eighth inch in diameter are already procurable, and these would give at least as good a representation as a newspaper print. But it is probable that smaller lamps could he made, by means of which finer results could he obtained. At present the. apparatus is complex and expensive, hut no doubt as time passes it will he simplified and cheapened, so that- wo may shortly he able to sit- at home in comfort and watch a thrilling run at an international football match ot the finish of the Derby.—(Chambers Journal).