A series of graphics, similar to a weapon rangefinder, and a small symbol display provide information about the ship's systems and condition instantly and continually to the commander; thus, the Jem'Hadar First and the Vorta can always be aware of their starship's battle capabilities, a point of vital importance to a militarily-minded warrior crew. The headset units can also relay other information, including ship-to-ship signals and subspace communications.
The headset viewer (1) is worn over the head with a data eyepiece on the left. A larger variant is also used by the Dominion in larger-scale operations, such as for fleet actions involving hundreds of starships or ground invasions.
These larger versions of the headset viewers (2) work on the same principles as the smaller devices, but are worn on the shoulder rather than over the head. These more substantial devices have a long black arm that pivots in several places so that they can be adjusted to fit the individual wearer.
Used by Dominion military commanders to plot the course of a multiple-unit operation, these headset viewers channel data on troop movements, enemy position and tactics, logistical concerns, and terrain straight to the eyes of those directing the battle.
In much the same way that individual Jem'Hadar Firsts or Vorta can manage their ship-to-ship combats, the Dominion commanders can instantly be made aware of any opportunities on the battlefield that may arise, and then take advantage of them instantly.
The shoulder viewers also work as two-way communicators; as information comes to the commanders, orders can be issued through subspace communications circuits inside the devices.
The headset and command viewers were designed specifically by the Dominion for use by the Vorta and the Jem'Hadar, but they can be used by any humanoid race. Humans appear to be unsuitable for prolonged use of the devices as they cause headaches and dizziness, but Cardassians can use them for hours at a time seemingly with no ill effects.
These headsets may at first appear to be a poor replacement for a viewscreen, but they seem to suit the servants of the Dominion perfectly well, and offer no tactical disadvantage. In the Dominion's view, the fact that the headset viewers leave only the commanders aware of the bigger picture is a distinct advantage as the troops are less likely to question their orders.