The sections on Telephony cover the installation, maintenance, and
operation of all standard types of telephone systems; they present
without prejudice the respective merits of manual and automatic
exchanges; and they give special attention to the prevention and
handling of operating "troubles." The sections on Telegraphy cover
both commercial service and train dispatching. Practical methods of
wireless communication--both by telephone and by telegraph--are
thoroughly treated.

The drawings, diagrams, and photographs incorporated into the
Cyclopedia have been prepared especially for this work; and their
instructive value is as great as that of the text itself. They have
been used to illustrate and illuminate the text, and not as a medium
around which to build the text. Both drawings and diagrams have been
simplified so far as is compatible with their correctness, with the
result that they tell their own story and always in the same language.

The Cyclopedia is a compilation of many of the most valuable
Instruction Papers of the American School of Correspondence, and the
method adopted in its preparation is that which this School has
developed and employed so successfully for many years. This method is
not an experiment, but has stood the severest of all tests--that of
practical use--which has demonstrated it to be the best yet devised
for the education of the busy, practical man.

In conclusion, grateful acknowledgment is due to the staff of authors
and collaborators, without whose hearty co-operation this work would
have been impossible.