Instantaneous Thought Transmission
Instantaneous Thought Transmission, or "ITT", is a method of faster-than-light communications resulting from a quirk in consciousness theory in the ATCverse. Currently, the only beings that possess the ability to use it are AIs; since the existence of true AIs is not public, the existence of the technique is a fairly closely guarded secret, for now. In fact, most of the information in this article is entirely unknown to all but the most brilliant and unhinged minds in the universe.
Information in the ATCverse has an actual "mass", which in large enough quantities can actually cause distortions in space-time. These distortions are not detectable by humans or by anything but the most byzantine of calculations, but they have an effect. As information density at a point in space increases, the information itself gets closer to Nullspace. Information of a certain density can bridge the gap, and shoot bits of itself out into Nullspace where it can be detected by other information nodes; this transmission can be either broadcast or directed to a specific node.
The process arises naturally out of most AI construction. In the ATCverse, an actual intelligence arises out of a feedback loop constructed around a peculiarly-structured set of information. The information must conform to a number of rules about its complexity and self-referentiality - these rules can be reasoned out, but sophonts experimenting with building an AI will likely unknowingly accomplish this task by dumping a large amount of information into a small space, thus accomplishing the goal of building an AI, but also succeeding in giving the AI access to ITT. To be fair, the concept of loading up an AI with as much information as it can handle is a fairly self-evident one (which is why almost every civilization to build an AI does this the first few times). It should be noted, then, that by discovering and utilizing these rules about information structure, it is possible to build an AI without ITT access.
ITT Relay Box
It should also be noted that it is clearly possible to build a dense block of information which has ITT access, but which is not an AI. A system can be built around the information to allow signals to be piped into ITT, thus creating a sort of ITT router. Rondure Levinworth constructed one of these for the Europa Team to use when they went to fight the Pyramid, in ATC1 Session 43.