LATE RESEARCH IN SPEECH PRODUCTION.

Star (Christchurch), Issue 18056, 17 January 1927, Page 6

LATE RESEARCH IN SPEECH PRODUCTION.

TELEPHONE, RADIO AND PERFECT REPRODUCTION. (Contributed.) It was mentioned in a recent issue that fundamentally the transmission of sound for the purposes of conversation was identtical whether the system used came under the category of radio or telephony as it is known to subscribers to an ordinary city exchange. Research in the older branch of the Science is entitled to an enormous amount of credit for the success that is now attending the efforts of recent years in the radio field. Developments have been more rapid and more clearly foreshadowed in radio only because of its dependence on telephone research generally. Since Graham Bell informed his assistant over the first completed telephone circuit that the world was on the verge of a marvellous discovery, the apparatus used has undergone tremendous changes and emerged from the crudest stages into that which can almost be designated human. The original receiver remains unaltered as the most efficient and delicate mechanical detector extant. On the other hand the transmitter has been made in various forms and sizes, all of which have proved more or less successful. Just as complex traffic problems have spurred telephone engineers on to the consummation of a mechanical switching system that would bring the human element down to an irreducible minimum, so have demands for long distant conversations spurred#the same officials on to the consummation of. a dependable telephone system that would be applicable where wires were impossible or otherwise unavailable. JThe telephone system, however, does not lead radio all the way. The vacuum tube invented by Fleming ostensibly for the detection of wireless waves was later improved and modified in a direction that enabled it to be used as a repeater on long distance telephone circuits. This is the. article that will make successful speech between subscribers in the northern and southern portions of New Zealand possible. Research in vacuum tubes has revolutionised radio and its older sister. In their present form these tubes can function as transmitters, receivers on “ boosters ” according to requirements. In radio they detect, rectify, amplify and magnify electric currents passing through the circuits of which they form a part. Another form of “ booster ” on tele-

phone circuits not familiar in this country is the loading coil used to artificially maintain the characteristics of the line wires at their most suitable values for clear speech of the required

volume. This artificial loading at prearranged and regular intervals counteracts the tendency of the line wires to distort and attenuate the rapidly changing sound wave impulses.

Research in connection with transmitting apparatus has resulted not Only in the perfect reproduction of the tone of the voice and articulation, but also in the outline of the speaker’s facial features at the same moment.

Another research development that has improved overseas cable transmission is the production of a highly nonmagnetic material called permalloy. The same principle of “ loading ” obtaining in the case of land lines for speeding up transmission is applied to submarine cables by means of permalloy wrappings.