P. & T. ENGINEERS

New Zealand Times, Volume XLVI, Issue 10614, 12 June 1920, Page 8

P. & T. ENGINEERS

PRESENTATION TO CHIEF THE SCOPE OF HIS INVESTIGATIONS. \i a mooting of the Institute of Post lin’d Telegraph Engineers, opportunity was taken to wish bon voyage to -W-r Shrimpton, ohief telegraph engineer, who is ' leaving for America ano Europe shortly to inquire into modern telegraph and telephone developments. Mr Shrimpton outlined the scope of his proposed technical (investigations while ahreiad. Suggestions relating thereto wero received from telegraph cn. gineers in various parts of the Dominion and discussed by those present. Doling the discussion reference was made loathe great strides that had boon made in all branches of telegraph and telephone engineering. Among the many subjects to bo investigated during the chief engineers visit to America and Europe, and which have a direct bearing upon the technical policy of the department, are the following ; _(l) Wireless telegraphy and telephony; (2) multiplex- wireless telegrapny ; i3> automatic telephone system; (4) multiplex telegraphy and telephony; (5) recent developments in submarine telephone cables mid telephonic transmission over long land lines; (,6j teloplionic repeaters for long lines. It must be understood (hat all the above have, been fully developed up to a commercial stage, Ho far wireless telephony over any considerable distance has mainly been, accomplished by expensive apparatus and large expenditure of energy. Multiplex wireless telegraphy is a development of the war period, and consists in the sending out of waves of different frequencies from the same aerial at the one time. In effect it enables one wireless station to send several simultaneous messages. By moans of a multiplex telegrapii system such as that which is shortly to be introduced into New Zealand, it is possible for one who has had no special training in tile Morse alphabet to send telegraph messages, the messages being signalled by depressing keys similar to those of a‘typewriter. Eight messages may pass over one wire at the same time and be automatically type-printed at the receiving station on the usual telegraph forms. In one system, at the completion of a message, the sending operator depresses a switch -which automatically turns over the page at the receiving end, leaving a fresh page exposed ready to receive the next xnes-

TELEPHONE TRANSMISSION.

With reference to "telephone transmission” it is found that speech is attenuated and distorted when speaking’ over submarine cables and over long Jaml iines, owinjy to the magnitude of a certain electrical property of telephone linos called "capacity.” Tho effect of this capacity can he overcome by the I insertion in the lino or cable at frequent intervals of vrhtrfc are called loading coils, which are coils of wire specially designed for the purpose. . As these loading; coils are comparatively large, and as they have to be inserted at frequent intervals, it will be seen that the cost of a cable is increased, as is the difficulty of laying and maintaining _it. Thera lire other developments winch overcome these mechanical difficulties, and these will come under the investigations of tho chief engineer. Telephone repeaters in their most modern form consist of what Is called in wireless work vacuum, tubes or thermionic valves. Instead of having ono long continuous line to talk over, the line is divided into separate parts, tho parts being separated from one another by means of telephone valves or relays, which repeat the voice currents into the adjacent section. The speech currents reaching the distant lend of the 'line are by this means made greater in volume than they would be if they had to traverse the whole length of the line without being reinforced. A PRESENTATION. After the, discussion, Mr .Slmimpton was presented on behalf of the institute with n smokers’ outfit. In making the prosentation Mr Gibbs referred to the fact that from the variety and complexity of modern telegraph and tiephono systems and apparatus, and the great development that has taken place of recent years, it would bo appreciated that Mr Shrimpton! would have e very strenuous ns well as intensely interesting mission. Various other, members also spoke, wishing Mr Shrimpton bon Voyage, to which Mr Shrimpton suitably responded.