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654
X. INTERNAL COMMUNICATIONS.
means of a method first employed by Professor Pupin, been artificially given
electric characteristics which make possible, on the one hand, a more distinct
transmission of speech over long lines, and, on the other, allow of the employment of a
cheaper material (wire of smaller dimensions) in the construction of such lines. The
total length of the Telegraph Service’s loaded bare wire- and cable circuits was,
at the close of 1913, some 29 967’6 km. On the whole, it may be said that
Sweden possesses one of the best constructed long-distance networks in the world.
A practical application of the progress made in telephone technics is the
so-called phantom lines, or the arrangement that three conversations are
transmitted simultaneously on two lines. As a result of the calculations and
inventions of Professor Pleijel, the devices employed for this purpose in the State
telephone network have reached an exceedingly high degree of perfection, and,
at the close of 1913, there were in use 9 846 km of such superposed connections.
It is two officials of the Telegraph Service, O. E. Egnér, C. E., and the
principal of the Service’s training school, G. Holmström, C.’ E., to whom
should be ascribed the honour of having invented the first practical
strong-current telephone for use on long lines. By its means, a conversation can,
without difficulty, be carried on over unloaded lines of ordinary dimensions
between Stockholm and Paris. The patent for Sweden has been bought by the
Telegraph Service, and a fairly large number of instruments is already in use.
Switch-boards and telephones were, at the beginning of the State Telephone
Service’s existence, for a long sequence of years, supplied by L. M. Ericsson’s
world-renowned factory, in Stockholm. Afterwards, however, the workshops of the
Telegraph Service gradually began to provide, on an ever increasing scale, the
telephones that were needed, and the establishment in question has also designed
and executed most of the new plants and carried out the necessary work for the
maintenance and improvement of the offices. Since, as mentioned above, the
Swedish Telegraph Service was among the first administrations that realized the
necessity of, and carried out, the change from single lines to double ones,
the exchange apparatus necessary for the new line-system had to be invented
and constructed within the country. The switch-board system employed at the
central and sub-exchange offices are, therefore, as a rule of Swedish manufacture.
The distribution system applied in Stockholm and Gothenburg, which has, too,
been adopted at Hamburg for an 80 000 lines’ plant was the invention of A.
Avén, telephone controller. The central-battery system, introduced at a number
of other offices, such as Malmö, Norrköping, Hälsingborg, Jönköping, Gävle,
etc., is a modification of the world-renouned system invented and manufactured by
the firm of L. M. Ericsson. Essential improvements in the old magneto system,
which is still made use of at smaller and medium-sized stations, have been
elaborated chiefly by A. H. Olssön, line-engineer, and have been utilized at the
stations at Härnösand, Karlstad, Kristianstad, Västerås, Östersund, etc.
Automatic exchange-stations, although on a small scale, on a system invented by G.
A. Betulander, C. E., engaged at the workshops of the Telegraph Service, have
been in use since 1903, and very promising experiments for larger stations have
been made by other officials of the Service. A central exchange for 2 000
subscribers, with a semi-automatic system on an American model, has just been
opened at Landskrona.
Chiefly in consequence of the well devised and well executed exchange systems,
but also as a result of systematic selection, exercise and superintendence of the
staff, the rapidity of service in the State telephone — offices has reached such a
degree of excellence that what, in many other countries, is merely a heart-felt
wish, is in Sweden already an accomplished fact. Even some ten years ago,
the average time elapsing between the subscriber’s making a call and his obtaining
a response from the attendant, at the largest exchanges in Sweden, had been
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