The Vox-caster is an Imperial radio communications transceiver that can be as small as a helmet-mounted link and as large as a massive bank of dedicated communications equipment employed at an Imperial military force's headquarters.
Usually a squad or platoon will have a link to their headquarters via one vox unit and smaller relays for trooper-to-trooper communications.
Command units usually use more complex versions of Vox-casters known as Master-Voxes. These pieces of communications technology can receive and transmit on multiple radio frequencies at once, making them ideal for coordinating the actions of multiple units at the same time.
In absence of any form of vox communications, troopers are taught to make use of sign language during battle.
The tech-priests of the Adeptus Mechanicus usually have Vox-casters implanted within their skulls as part of their cybernetic enhancements, a common upgrade for all the servants of the Machine God. Most of these Vox-casters are short-ranged and used only for intersquad communications.
- Codex: Imperial Guard (3rd Edition, 2nd Codex), pg. 36
- Warhammer 40,000: Wargear (2nd Edition)
- Warhammer 40,000: Wargear (4th Edition)