The CB Radio (CB = Citizens' Band) is Dead Frontier's chat room network, which is practically always active and full with people talking, trading, planning or plotting, depending on your currently active chat channel. You can join the CB Radio anytime by clicking the green radio, which can be found at the bottom of the screen (in an outpost) or below the game screen (in the Inner City). There are also some special rules for the CB Radio, which are separate from the main Dead Frontier Rules, yet a very important read before you chat the first time. They can be found here: CB Radio Rules