DarkDot SOI
Signal Operating Instructions
A classified publication containing call signs, frequencies, authentication tables, codewords, and challenge/password sets used to maintain secure and effective communications within an operation.
The SOI (sometimes called CEOI — Communications-Electronics Operating Instructions) is the communications bible for an operation. Every radio operator must know how to use it without prompting.
Contents of an SOI
- Call signs: Assigned designators for each element (e.g., WOLF 6 for the company commander)
- Frequencies: Primary and alternate for each net (command, admin/log, fires, aviation)
- Authentication tables: Challenge/response matrices for verifying station identity
- Codewords: BREVITY terms, code names for objectives, and status reports
- Challenge and password: Running password system for IFF (identification friend or foe) at ground level
- Number code: Encrypted numeric references for sensitive locations
Operations Security
The SOI is a classified document handled under strict controls. It changes on a defined cycle (typically daily or per-operation). Compromise of the SOI requires immediate frequency and call sign changes across the entire net.
Communicationscommssignalssecurityradioclassified