Whistle can be heard up to 1km from origin. These codes should only be used by the Company or lead element when dispersing commands to the entire ground force. Exceptions may be made during long distance operations where individual sections have their own areas of operation.
Terminology:
Dot - A short burst into the whistle.
Dash - A long burst into the whistle
Blast - Several consecutive short bursts into the whistle
Code
HALT - 1x Dash
ADVANCE - 2x Dot
RALLY - 3x Dot
RETREAT - 1x Blast
Within the 9ACG, each section has it's own color code for marking purposes.