In each of the seven major city districts (with the exception of Sheldon Park and the Gotham Pioneers Bridge), there is a communications tower (the red icons on the world map). All of these are inactive at first and putting them back online is connected with one of the side missions, where you need to deal with Enigma, one of the most famous villains in Gotham.
In most cases, putting a tower back online is not that easy, because Batman first needs to deal with one or several groups of bandits, and also find a way to get to the control panel, in order to hack into the system. In spite of these handicaps, I recommend that you turn your interest to activating, at least, some of the comms towers soon after the game starts. This is so, because activating a tower activates two other items in that district. These are:
- Batwing drop point, i.e. the fast-travel point. This is one very useful function, thanks to which you will not need to waste time while exploring the game world.
- Revealing of the Network Relays locations. Knowing this will help you complete one of the parts of Enigma's side mission.
Note - some of the towers (e.g. the one in the Amusement Mile ) may be activated only after you obtain the required gadgets so, do not worry if you will not be able to achieve success at first.