CHAPTER   XXI

RECEIVING  APPARATUS  FOR  WIRELESS  TELEPHONY  .  .       309

Quantitative  response  of  detectors — Magnetic  and  electrolytic
detectors — Crystal  detectors — Characteristic,  sensitiveness  and
response  curves  for  detectors — Vacuum  detectors — Valves  and
Audions — Properties  of  Audion  detectors  and  Audion  amplifiers
— Heterodyne  receivers  for  speech—  The  ultraudiou  receiver.
xii  TELEPHONY  WITHOUT  WIRES

CHAPTER   XXII

PAGE

KECEIVING  AMPLIFIERS         .  .  332

Types  of  amplifiers — Microphonic  amplifiers — Brown's  tele-
phone relay — Electron  and  vacuum  amplifiers — High-frequency
amplification — Use  of  "return-coupling" — Audion  amplifier  and
crystal  detector — Combined  valve  amplifier  and  detector — Low-
frequency  amplification — Crystal  detector  and  Audion  amplifier —
Multivalve  amplifiers.
CHAPTER   XXIII

INTERFERENCE  PREVENTION.  .         :    .  .  .       347

Interference  from  other  stations  and  by  atmospherics — Methods
of  reducing  interference — Balanced  aerials — Balanced  valves  and
balanced  crystals  —  Austin's  interference  preventer  —  Vacuum
valve  interference  limiter  —Effect  of  type  of  receiver  upon  response
to  atmospherics — Atmospheric  interference  and  the  limitation  of
amplification.
CHAPTER   XXIV

FIELDS  OF  USE  FOR  WIRELESS  TELEPHONY  .  .       356

Competition  with  wire  telephony — Use  of  wireless  where  wires
cannot  be  maintained — Communication  with  railway  trains  —
Trans-ocean  work — Wire  telephony  by  cables— Attenuation  and
distortion  —  Ship-to-ship  and  ship-to-shore  work  —  Essential  •
.  features  of  practical  wireless  telephone  apparatus — Relaying  on
to  land  lines  —  Duplex  working  —  Comparison  of  the  various
methods.
