contents - History of Ericsson - History of Ericsson

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and the brothers Erickson of the Strowger Company who constructed the first
automatic telephone exchange with group selectors and final selectors. It was
installed during 1897 at Augusta, Ga.
This paved the way for large automatic exchanges and the first plant for
1 000 subscribers came into existence in December 1900 at New Bedford,
Mass. It was followed the next year by a similar but improved exchange at
Fall River, Mass.
Call meters came into use in 1902 at a 10 000 line exchange in Chicago. The
device was necessitated by the telephone charge being reckoned per call. The
meters employed recorded all connections established, no matter whether
answer was obtained or not. On the other hand calls were not counted in the
event the called number was busy.
In 1904 the Strowger Company introduced the pre-selector, the Keith preselector,
at an exchange in Wilmington, Del. In earlier plants there had
been a first group selector for each subscriber's line. Thanks to the preselector
it was now possible for 100 subscribers to make use of ten first group
selectors in common. This meant a saving of 90 % in the cost of first group
selectors. Of course, there was the expense of pre-selectors, but the final
gain was still considerable.
Up to the years 1904—1905 local batteries were employed at all automatic
exchanges for microphone feed. The advantages of the central battery system
were becoming more and more recognized and it was therefore quite natural
that the question of its adoption also for automatic exchanges became nunc
discussed. It was done for the first time with the exchange at South Bend,
Ind., completed in May 1905, this being moreover the first exchange which
had pre-selectors, first and second group selectors, final selectors and call
meters, that is a connecting scheme in which even the automatic technician
of our day would be quite at home.
The machine-driven automatic systems were due to the brothers George,
James Hoyt and Egbert S. Larimer. The middle of the three was originally
a lawyer, but a lawyer in the predicament that his life interest was electrical
experimenting. He quickly abandoned the law — his employer not being the
least to encourage the change — and sought contact with Romaine Callender
who had already given proof of his inventive talent by a design for organs.
These two along with the other Lorimer brothers established in 1896 the
Callender Telephone Exchange, which company —• Callender having by then
quitted it — made application on 24th April, 1900, for patent relating to the
first machine-driven automatic system.
Clement in 1910 constructed the first automatic relay system.
Naturally it was the United States which first gained the benefit of the
new technics. It was only in 1898 that Europe came into close contact with
it, when A. E. Keith demonstrated a trial plant at London before a representative
gathering of telephone technicians. In the summer of 1899 an
exchange of 400 numbers was ordered for Berlin. It was put into service in
1901. It was not, however, until around 1910 that any large automatic
telephone plants came into existence in Europe and then it was at Graz and
Munich.
By 1912 there were 131 automatic telephone exchanges in the United States.
The largest were Los Angeles with 24 000 subscribers, San Francisco with
16500 subscribers, Columbus with 14000 subscribers, Portland with 12000
subscribers and so on. At Chicago there was at that time an exchange for
20 000 subscribers under construction.
In Europe in the same year the number of automatic exchanges was comparatively
small. Within the German Empire postal union there were automatic
or semi-automatic exchanges at Hildesheim, Altenburg, Dalgow, Raesen,
Dornarp, Neudietendorf and Durrheim. Exchanges at Posen and Dresden f° r