Radio Broadcast (May 1928-Apr 1929)

384 RADIO BROADCAST ADVERTISER ill OS If r J The Nerve Center of Your Radio BECAUSE Cunningham Radio Tubes carry the true tone and reproduce pure harmony, they are rightly called the nerve center of your radio. Tubes that have had long, constant use should be replaced with new, correct Cunningham Tubes to enable you to enjoy modern broadcast reception. I Never use old tubes ^71 with new ones — use |» new tubes throughout JJ E. T. CUNNINGHAM Inc. New York Chicago A Austria's president signs a "fultograph" Dr. Siepel, President of Austria, is at the left, signing a photograph of himself transmitted by radio by the method perfected by Captain Otho Fulton {in the center, with his hand on the table). Captain Fulton developed his apparatus, the "Fultograph" , in Vienna; the British Broadcasting Company is now considering its adoption. By WILLIAM J. BRITTAIN R EGULAR broadcasting of pictures is promised for Great Britain by October. The British Broadcasting Corporation is now considering the adoption of the "Fultograph," the apparatus of Captain Otho Fulton, an Englishman who has been experimenting in Vienna for three years. Captain Fulton gave me a demonstration of his apparatus when I met him in Vienna. The photograph to be transmitted is printed on a copper foil coated with sensitized fish glue. Exposure to light makes part of the glue surface insoluble. Washing removes the soluble parts, which have not been exposed to light, and a half-tone picture in glue is left. The foil is then placed on the transmitting machine. All you can see is a box containing a small clockwork motor, and at the side a cylinder which can move slowly round, like the one on Edison's first phonograph. The foil is wrapped round the cylinder, which is then set going. Over the foil a metal needle passes. When the needle is touching a part of the bare foil a current passes and is transmitted. When it touches a part where the glue is, the glue acts as an insulator, and no current passes. In receiving the picture broadcasts a one-tube set is sufficient for distances within a mile of the broadcasting station; for greater distances a receiver of two or more tubes is necessary. You can hardly tell the receiving set from that at the transmitting end. Round the brass cylinder a piece of paper dipped in chemicals, and still damp, is placed. A platinum needle passes over it, and when current is being sent out at the transmitting end a current passes between the needle and the cylinder, and the paper is stained brown through the action of the current on the sensitized paper. Thus the picture is traced out. In his early experiments, Captain Fulton told me, he synchronized reception and transmission by means of a pendulum device devised by himself and Mr. T. Thorne Baker, of London, with whom he formerly collaborated. Both receiving and transmitting instruments were fitted with a long pendulum which made an electric contact at every beat of i| seconds and released the cylinders for a new revolution. With this method it was found that unless there was absolute stability, the picture was ruined; so now Captain Fulton has devised a series of relays giving him electro-magnetic synchronization. This enabled him in a test to take his apparatus on a ten-day steamboat trip along the Danube and receive pictures from his laboratory in Vienna during the entire trip. The fact that the glue on the copper foil is easily scratched calls for some remedy. One is to "burn in" the picture; another, used by Thorne Baker, is to roll the glue picture between polished steel, so that the picture sinks into the metal, like a picturesque commutator. For the chemicals in which the semi-absorbent paper is dipped, several mixtures are used. One is a potassium iodide and starch solution, which gives a coloration with the passage of a current of less than two milliamperes; and another solution, used in the Jenkins laboratories, contains ammonium nitrate, ammonium chloride, and potassium ferrocyanide. "All the time I have tried to simplify radio picture apparatus for the man at home," Captain Fulton told me. " I consider my latest apparatus is as simple as a cart: a cart has only the wheels and the body, and if you take either away it isn't a cart any more. My assistants and 1 have worked hard and now we have made a home set to be sold to the public for about seventy-five dollars. They have already been adopted in Vienna." The pictures are 45 inches by 3J inches, and those I saw received were as distinct as hurriedly produced newspaper photographs.