Rules demonstrate communication is possible. Vertical or Horizontal between units. HQ's receive contact icons they can order fire missions for their subunits to carry out if they all have their 'Green Radiobuttons'. I enjoy my Hotseat battles as winning or losing is not important finding tactical solutions is the reason we play the game. Important during the set up period make sure the 'Signals' are in order. There should be Signal units like we have Engineers who establish communication between Armored HQ and Infantry HQ for example. Signal unit clicks HQ A and HQ B after some time the Signal unit displays a Radio Icon.