by such an arrangement of local trunks, but the growth in lines and in
traffic has developed in most instances certain weaknesses which make
it advisable to find speedier, more accurate, and more reliable means.

For the serving of a large traffic from a large number of lines, as is
required in practically every city of the world, a very great
contribution to the practical art was made by the development of the
multiple switchboard. Such a switchboard is merely such a device as
has been described for the simpler cases, with the further refinement
that within reach of each operator in the central office appears
_every line which enters that office_, and this without regard to what
point in the switchboard the lines may terminate for the _answering_
of calls. In other words, while each operator answers a certain
subordinate group of the total number of lines, each operator may
reach, for calling purposes, every line which enters that office. It
is probable that the invention and development of the multiple
switchboard was the first great impetus toward the wide-spread use of
telephone service.

Coincident with the development of the multiple switchboard for
manually operated, central-office mechanisms was the beginning of the
development of automatic apparatus under the control of the calling
subscriber for finding and connecting with a called line. It is
interesting to note the general trend of the early development of
automatic apparatus in comparison with the development, to that time,
of manual telephone apparatus.

While the manual apparatus on the one hand attempted to meet its
problem by providing local trunks between the various operators of a
central office, and failing of success in that, finally developed a