[Illustration: A TYPICAL CENTRAL OFFICE FOR RURAL EXCHANGE Line
Protectors on Wall at Left.]




Foreword


The present day development of the "talking wire" has annihilated both
time and space, and has enabled men thousands of miles apart to get
into almost instant communication. The user of the telephone and the
telegraph forgets the tremendousness of the feat in the simplicity of
its accomplishment; but the man who has made the feat possible knows
that its very simplicity is due to the complexity of the principles
and appliances involved; and he realizes his need of a practical,
working understanding of each principle and its application. The
Cyclopedia of Telephony and Telegraphy presents a comprehensive and
authoritative treatment of the whole art of the electrical
transmission of intelligence.

The communication engineer--if so he may be called--requires a
knowledge both of the mechanism of his instruments and of the vagaries
of the current that makes them talk. He requires as well a knowledge
of plants and buildings, of office equipment, of poles and wires and
conduits, of office system and time-saving methods, for the
transmission of intelligence is a business as well as an art. And to
each of these subjects, and to all others pertinent, the Cyclopedia
gives proper space and treatment.