scmJS docs

Transmission

A message from a unit: the unit type's portrait talks, the text is shown, the sound plays and the location is pinged on the minimap. Like a Wait, it holds the rest of the trigger until it is over. How long that is starts from the sound's length (WAV duration) and is changed by the modifier and Duration: Set To replaces it, Add and Subtract change it.

Action 7 · Transmission(Display, Text, Unit, Location, Modifier, Duration, WAV, WAV duration);

Argument Takes Stored in the action
Display Always Display or Don't Always Display bit 0x04 of byte 28
Text text, stored as a string-table entry bytes 4–7
Unit a unit type, or one of the unit classes bytes 24–25
Location a location (Anywhere is location 64) bytes 0–3
Modifier Set To, Add or Subtract byte 27
Duration a time in milliseconds bytes 20–23
WAV the name of a sound file in the map, stored as a string-table entry bytes 8–11
WAV duration a time in milliseconds bytes 12–15
Transmission(Always Display, "Hold this position.", "Jim Raynor (Marine)", "Base", Add, 0, "staredit\\wav\\raynor.wav", 2400);