DEFENSE SWITCHED NETWORK
The Defense Communications System (DCS)
Defense Switched Network (DSN) is a
telecommunications telephone interconnected
network. This system is found on most military and
other Federal Government installations in the United
States and overseas.
This system upgraded the Automatic Voice
Network (AUTOVON) and will evolve into an all-
digital network in the 1990s. The DSN incorporates
capabilities that were not available in the AUTOVON
system, such as automatic callback, call forwarding,
call transfer, and call waiting.
Precedence of Calls
The precedence of a call indicates the degree of
preference to be given a call relative to all other calls in
progress. A preemption feature provides the ability to
disconnect a call of lower precedence and seize the
access line or interswitch trunk to complete a call of
higher precedence. A unique aspect of the DSN is that
switches have been programmed to determine what
precedence treatment must be given each call.
The combined features of precedence and
preemption used in DSN are called multilevel
precedence and preemption (MLPP). The effectiveness
of this system depends on the proper use of the
precedence system by the users.
All users should be familiar with the system and the
types of calls assigned to each precedence. Each user
should ensure that his or her call is not assigned a
precedence higher than that justified by the
circumstance or information involved.
The DSN offers five types of call treatment. The
precedences and their applications are listed below in
relative order of priority in handling.
FLASH OVERRIDE (FO) FO takes
precedence over and preempts all calls on the DSN and
is not preemptible. FO is reserved for the President of
the United States, Secretary of Defense, Chairman of
the Joint Chiefs of Staff, chiefs of military services, and
others as specified by the President.
FLASH (F) FLASH calls override lower
precedence calls and can be preempted by FLASH
OVERRIDE only. Some of the uses for FLASH are
initial enemy contact, major strategic decisions of great
urgency, and presidential action notices essential to
national survival during attack or preattack conditions.
IMMEDIATE (1) IMMEDIATE precedence
preempts PRIORITY and ROUTINE calls and is
reserved for calls pertaining to situations that gravely
affect the security of the United States. Examples of
IMMEDIATE calls are enemy contact, intelligence
essential to national security, widespread civil
disturbance, and vital information concerning aircraft,
spacecraft, or missile operations.
PRIORITY (P) PRIORITY precedence is for
calls requiring expeditious action or furnishing
essential information for the conduct of government
operations. Examples of PRIORITY calls are
intelligence; movement of naval, air, and ground forces;
and important information concerning administrative
military support functions.
ROUTINE (R) ROUTINE precedence is for
official government communications that require rapid
transmission by telephone. These calls do not require
Local command policy normally states that the
DSN is to be used only for the most essential official
calls. The DSN system must never be used to make
personal or unofficial calls.
Telephone circuits, particularly those routed by
high frequency and microwave, are susceptible to
monitoring and interception. The DSN is not a secure
system! Users must take care and use common sense to
avoid divulging classified information. Giving hints or
talking around a classified subject can lead to the
compromise of classified information.
TRANSMIT MESSAGES VIA MANUAL
In these days of super speed burst message
transmission the use of manual relaying or transmitting
of messages is not the norm. You should locate, identify,
and use locally produced instructions, publications, and
ENEMY CONTACT REPORTING
Enemy contact reports are normally made only
once when you are in direct communications with the
officer in tactical command (OTC), a higher authority,
or a shore radio station. Enemy contact reports are
signaled using basic R/T procedures as modified by
chapter 6 of ACP 125. Details of enemy contact