language difficulties. Each word is accented on the
capitalized syllable. You should memorize the phonetic
alphabet and use it along with correctly pronounced
numbers, as described earlier in chapter 3, for all
telephone and lookout reports.
REVIEW 1 QUESTION
Q1. You are manning the sound-powered telephone
in a repair locker. DC central calls and wants the
serial number of the P-100 pump (23DBCX14)
in your repair locker. How should you say this
number over the phone?
SOUND-POWERED TELEPHONES
Learning Objectives: When you finish this chapter,
you will be able to—
R e c o g n i z e
t h e
c o m p o n e n t s
o f
t h e
sound-powered telephone.
Identify the procedures to follow when using
sound-powered telephones.
Sound-powered phones are just what the name
implies—phones that operate on your voice power and
require no batteries or external electrical power source.
When you speak into the mouthpiece, the sound
waves of your voice cause a diaphragm to vibrate. The
vibrations are transferred from the diaphragm through a
drive rod to an armature centered in a wire coil. The coil
is located in a magnetic field supplied by two permanent
magnets. Movement of the armature in the magnetic
field causes a current to be induced into the coil. The
current then is transmitted to a receiver (the earpiece)
where the process is reversed, and the person at the other
end of the circuit hears the same sounds you
transmitted.
The mouthpiece and earpiece, though shaped
differently, function in the same manner and thus can be
used interchangeably. You can talk into an earpiece and
hear through a mouthpiece. This feature is important to
remember not only in the event of a breakdown of one or
the other pieces but also because undesired noises can
be fed into the system through an earpiece turned away
from your head.
THE HEADSET
Figure 4-1 shows a headset type of sound-powered
telephone. The mouthpiece is suspended from a yoke
that is attached to a metal breastplate. The earpieces are
connected by an adjustable band. The mouthpiece and
earpiece are connected by wire from a junction box on
the breastplate. The plug cord is also connected into this
junction.
The headset is delicate and can be easily damaged.
When you pick up the set to put it on, hold the entire unit
in your left hand. You will find the headset is hung over
the transmitter’s supporting yoke and the lead wires are
coiled.
To put the gear on—
1. Unhook the right side of the neck strap from the
breastplate, put the strap around your neck, and
then fasten it to the breastplate again.
4-2
Student Notes:
Figure 4-1.—Headset.
