Corrected entry: To speak to each other when they are out of the range of hearing each other, they have communication devices around their necks and they press it when they want to talk. But quite a few times sometimes they use it and sometimes they don't, eg, when Jake goes out with Sigourney in the helicopter, as Avatars, Jake wanders off and Sigourney speaks to him through the communications device, but later, when they are the same distance apart, she just talks to him normally.
kh1616
24th Feb 2014
Correction: He's within hearing range, so choosing whether or not to use the radio isn't really a mistake.
Phixius ★