It is a device used by the Intelligence Division of the Allied Shinobi Forces in order to pass information to each other be it from the headquarters to the field ninja or between battalions and vice versa. There are two variants to the device:
The stationary device which is much bigger is attached to two batteries and has a headset that covers the upper half of the user's face completely.
The portable version however, is much smaller and only has a wire running from the device to the user's head and can be carried on their back.
The version at the shinobi headquarters is simply a larger version of the stationary field ones with more batteries attached to it, and has three people stationed at it.