sound signals. As a Seabee, you normally use the radio
as the main source of communication while on a convoy
because most of your vehicles have radios mounted in
them.
Normally, wire and messengers are the primary
means of communication in defense. Radio is used when
wire service is interrupted after the enemy has made
contact or when ordered by a higher command. Two or
more wire lines should be installed over different routes
to connect two units. This allows communication to be
quickly reestablished if one line goes out. Visual and
sound signals may be used to supplement wire in the
defense, but only when they do not compromise
security.
Visual signals include panel sets, pyrotechnics,
Figure 11-1.--Radio Set AN/PRC-77 components.
smoke of various types and colors, arm and hand signals,
flashlight, tracer ammunition, improvised lights, and
flags. Higher headquarters normally prescribes the use
of pyrotechnics or smoke signals to call for shift, lift,
TA-312/PT and TA-1/PT telephones
fire, or illumination.
1. The TA indicates the type of equipment
Sound signals are normally used for alarms to warn
(telephone apparatus).
of air, chemical, biological and radiological (CBR), or
2. The numbers 312 and 1 indicate the model
ground attack Whistles, horns, bells, small arms, or
other noisemakers may be used for sound signals.
numbers.
No matter what type of communication is used,
3. The P indicates the installation (pack,
assume that you are being monitored by the enemy. This
portable).
is particularly true of radio, which is the LEAST secure
4. The T indicates the type and purpose of the
means of communication.
equipment (telephone [wire] transmitting).
SB-22/PT switchboard
1. The SB indicates the type of equipment
UNDERSTANDING RADIO AND
(switchboard).
TELEPHONE NOMENCLATURE
2. The number 22 indicates the model number.
The radios, telephone, and the switchboard
3. The P indicates the installation (pack,
discussed in this section are those presently on the
portable).
NMCB Table of Allowance (TOA). To help you
4. The T indicates the purpose of the equipment
understand the component nomenclature and their
(telephone [wire] transmitting).
family names, the following examples are provided:
AN/PRC-77 and AN/PRC-104 radios
AN/PRC-77 Radio
1. The AN indicates the users (Army/Navy).
2. The P indicates the type of installation (pack,
The AN/PRC-77 radio set shown in figure 11-1 is a
portable).
short-range, man-packed, portable, frequency-
modulated (FM) receiver-transmitter used to provide
3. The R indicates the type of equipment (radio).
two-way voice communication. The AN/PRC-77
4. The C indicates the purpose (communi-
operates on low power and at very high frequencies
cations).
(vhf). The location of the equipment greatly affects its
5. The numbers 77 and 104 indicate the model
operating range. Normally, a line-of-sight range can be
numbers.
expected; that is, when the other station can be seen,
11-2