Signal operating instructions (SOI) or Communications-Electronics Operation Instructions (CEOI) are U.S. military terms for a type of combat order issued for the technical control and coordination of communications within a command. They include current and up-to-date information covering radio call signs and frequencies, a telephone directory, code-words (for rudimentary encryption), and visual and sound signals. A designated

battalion A battalion is a military unit, typically consisting of up to one thousand soldiers. A battalion is commanded by a lieutenant colonel and subdivided into several Company (military unit), companies, each typically commanded by a Major (rank), ...

signal officer prepares the battalion SOI in conformance with the SOI of higher headquarters. During operations, SOI are changed daily. Since the fielding of the

SINCGARS Single Channel Ground and Airborne Radio System (SINCGARS) is a VHF combat network radio (CNR) used by U.S. and allied military forces. In the CNR network, the SINCGARS’ primary role is voice transmission between surface and airborne comman ...

system, however, the paper SOI has generally faded from Army use. Electronic SOI are now generated, distributed and loaded along with

cryptographic keys A key in cryptography is a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data. Based on the used method, the key c ...

. The title SOI was used until the early 1970s and it was changed to CEOI and then changed back to SOI in the 1980s.

References

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External links

Sample SOI, FM 11-1 Appendix C
Key management Military radio systems Military terminology