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 preferential handling. Security 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 CIRCUITS 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 references. 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 1-19