Soldier Combat Skills

Chapter 11-3 Communications Security

Communications security (COMSEC) consists of measures and controls to deny unauthorized persons information from telecommunications and ensure authenticity of such telecommunication. COMSEC material includes–

  • Cryptographic security.

  • Transmission security.

  • Emission security.

  • Physical security.


11-5. Classified material, protected against unauthorized access, is information produced and owned by the US Government. Authorized access to (clearance to view) classified material requires a NEED-TO-KNOW designation and the appropriate security clearance. Responsibility to protect security of the material rests with the individual handling it. No person is authorized based solely on their rank, title, or position. They are only authorized by their classification level. The three levels of security classification (clearances) follow:

Top Secret–This classification applies to material that could cause exceptionally grave damage to national security.

Secret–This classification applies to material that could cause serious damage to national security.

Confidential–This classification applies to material that could cause damage to national security.

Note: "For official use only" (FOUO) is a handling instruction, not a classification.


11-6. The SOI is a COMSEC aid designed to provide transmission security by limiting and impairing enemy intelligence collection efforts. The SOI is a series of orders issued for technical control and coordination of a command or activity. It provides guidance needed to ensure the speed, simplicity, and security of communications.


  • Training SOI……… Unclassified or FOUO.

  • Operation SOI……. Used only when deployed for mission.

  • Exercise SOI……… Used for field training exercises.


  • Call signs.

  • Frequencies.

  • Pyrotechnics.

  • Challenge and password.


11-7. The ANCD (Figures 11-2 and 11-3) is a handheld device that allows users to store/transmit data via cable and retrieve COMSEC. It is enabled for night viewing. It also features a water resistant case and sufficient backup memory.


11-8. The main menu has three choices:

  • SOI pertains to SOI Information.

  • Radio pertains to COMSEC keys/FH data to be loaded into the radio.

• Supervisor pertains to areas performed by the supervisor only.
11-9. To select areas of the main menu–

  1. Use the ARROW key function by pressing
    either the left or right arrow keys, and then
    press the ENTER key.

  2. Press the corresponding capital letter on


the keyboard to take you directly to

SOI Radio sUpervisor

a specific topic:

S Signal operating instructions
R Radio
U Supervisor


11-10. Call signs have two parts (Figure 11-4):

  • Designation call sign identifies the major unit (corps, division, brigade, or battalion).

  • Suffix and expanders identify individuals by position.


11-11. Set times (Figure 11-5).

  • Ten time periods in an SOI, which change by calendar day at a designated time (typically 2400Z).

  • Each time period has a different call sign and frequency for each unit.

  • ANCD breaks them into 2 SETS: TP: 1-5 and TP: 6-10.

Note: Follow unit SOP for preventive and immediate action measures for capture or compromise of SOI or systems.

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