Orallity - Human-based connections, non-linear presented in linear story. Extremely dynamic. Between an oral tradition and the beginning of the written word came the town cryer. Bringing a common message to different towns, but still varying the delivery.
Written - Beginning of linearity and power-structures (religion uses the power of linearity). Between the written word and the advent of the printer was scribes, whose sole purpose was to transcribe the bible from one copy to the next.
Printed - The slow removal of power-structures. A move towards equality and shared knowledge (extremely linear).
Electronic - The return of dynamic authoring. The appearance of technology into the power structure.
The cyclical theory is based on the idea that history is continually repeating itself, with different people and technologies working within the exact same structure.
Based on the idea that people and technology will continue going in a direction until they go to far, then there will be a reaction pushing everything in the opposite direction.
Power greatly comes directly into play when talking about shift in communication, due to the fact that the barriers between people and the major modes of communication limit the number of voices that can be heard. Electronic media has a flattening effect on the voices...however it also has a pretty high barrier to entry.