The Telephone System of To-day

New Zealand Tablet, Volume XXXV, Issue 3, 17 January 1907, Page 15

The Telephone System of To-day

Since its first invention, the only alteration in ■ the telephone itself (says ' Indian Engineering ') has been the substitution of a new form of transmitter : "instead of .relying solely upon the energy contained- 'in spoken sound, an , battery supplies the current while vibrations initiated by\ the voice" simply ' cause fluctuations in this current by varying the pressure between contacts in the circuit, and thereby altering its resistance.- "the usual form taken by these contacts' isthat between^ granules of hard carbon resting between two carbon discs ; but this arrangement may be varied in almost any manner without affecting qualitatively the essential result : piles of. nails, plumb-bobs touching mercury, streams of conducting solutions, and the arc light itself, have served by way. of experiment ; while in place of. the ordinary diaphragm, boiler heads an inch Jbhick, and even the sides of steamships have been used. - These, taken especially in connection with the most surprising fact that variations in pressure between two surfaces in contact affect resistance iq the same ratio as do fluctuations in the distance of an armature aflectr -the .strength of a magnet, are most highly suggestive concerning the nature- of magnetism itself ; but, resisting, temptation: to- theorise on the subject, we would" rather turn towards- those developments which have rendered the telephone system of~ to-day one of the most successful among engineering enterprises. The lesson here' taught:- is highly ' moral :_ results have not been obtained by" fortunate guesses or by lucky inventions, but have followed - as the certain reward of sound administration-- and the concentration of many minds on one object. The Switchboard " - —without which the commercial success of " the" system would be impossible— is the product oorf r nearly as many minds as- it has terminals. The : cost of a switchboard, of course, increases much more rapidly, than does the number of subscribers for which it provides': clearly the number of connections required for.tf subscribers varies .as n"2 — n ; and with, all our present methods of_ special machinery and the organised application of skilled labor, it requires as" long to make and instal a- large switchboard as it does to "build 1 and equip a merchantman. A minute glow-lamp' has replaced the old drop-shutter as signal ; and a ' click ' heard by the operator on inserting the second plug serves to" indicate' that the -desired line is in use -elsewhere. " A switchboard for Kg ooo telephones . has tw^> and a, ' half million soldered connections and 10,000 _miles"' of wire. "~"~ ■_ ■ *"~ -. /. - . „.- . Turning to the '.telephone. .line,- -perhaps our most important invention in this respect is that" of Mr. " Doolittle—the production-' of hard-drawn copper wire : which alone has rendered possible self-supporting aerial- wires of -copper. Interference by induction in the case of overhead wires is minimised • by transposing the telephone wires to various positions on the cross-arms, while the wires of underground- cables are laid in twisted pairs so as to be immune to inductive influence. '"An' aVmy of 'workers* exposed to every vicissitude of climate, and one-third of the gross revenue of - a telephone company are devoted to "maintenance alone. It was estimated, that during a recent winter in North America damage done to aerial lines of" all sorts in the New England. States exceeded Ihe whole loss from .shipwreck on the corresponding coast line. " . ' Most of the troubles of the "telephone linesman are shared by his elder brother in the telegraph ' department. The first lines erected in Mexico were quickly wrecked ' by. parrots and ring-tailed monkeys who nightly visited them J in great numbers- for gyibnastic exercise. - The line - run by the King of the Belgians across his territory in Central 'Africa- was" •• carefully supported on iron poles so' as to be safe against the attacks of white ants, but the sportive and humorous elephant exhibits a lively curiosity concerning *.„ the roots of. .these strange- trees : doubtless — being an optimistic gentleman— he concludes frpm the ..non-edible nature of' the insulators and wires -that the succulent portion of these plants must be situated near their lower extremities. - t Bears have been known to. "-gnaw down wooden poles in search of that hidden hive from which proceeds the ceaseless humming ; and along the South. Atlantic coast fish-hawks build upon the poles and fiercely attack intruders, while in some countries wasps find homes beneath the hollow insulators. Truly the linesman's lot, though lively, is not a wholly happy one.