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.

Table of Contents

VOLUME I

FUNDAMENTAL PRINCIPLES _By K. B. Miller and S. G. McMeen_[A]

Acoustics--Characteristics of Sound--Loudness--Pitch--Vibration of
Diaphragms--Timbre--Human Voice--Human Ear--Speech--Magneto
Telephones--Loose-Contact Principle--Induction Coils--Simple Telephone
Circuit--Capacity--Telephone Currents--Audible and Visible
Signals--Telephone Lines--Conductors--Inductance--Insulation

SUBSTATION EQUIPMENT _By K. B. Miller and S. G. McMeen_

Transmitters--Variable Resistance--Materials--Single and Multiple
Electrodes--Solid-Back Transmitter--Types of
Transmitters--Electrodes--Packing--Acousticon Transmitter--Switchboard
Transmitter--Receivers--Types of Receivers--Operator's
Receiver--Primary Cells--Series and Multiple Connections--Types of
Primary Cells--Magneto Signaling Apparatus--Battery Bell--Magneto
Bell--Magneto Generator--Armature--Automatic Shunt--Polarized
Ringer--Hook Switch--Electromagnets--Impedance, Induction, and
Repeating Coils--Non-Inductive Resistance
Devices--Differentially-Wound Unit--Condensers--Materials--Current
Supply to Transmitters--Local Battery--Common Battery--Diagrams of
Common-Battery Systems--Telephone Sets: Magneto, Series and Bridging,
Common-Battery

PARTY-LINE SYSTEMS _By K. B. Miller and S. G. McMeen_

Non-Selective Party-Line Systems--Series and Bridging--Signal
Code--Selective Party-Line Systems: Polarity, Harmonic, Step-by-Step,
and Broken-Line--Lock-Out Party-Line Systems: Poole, Step