In 6DKF we distinguish 2 types of alarm bells, of "signals" that precede an attack:
The sudden signals are those that can be noticed only if we are 100% focusing our attention on our opponent, they are micro-signals that precede an attack in the nearest time (fractions of a second).
The contextual signals are those that give us, in real life situations, the time to get away, to get ready to fight or to keep quiet so as not to to fight (some more seconds).
For instance, in the situation where we have not been attacked we talk about contextual signals (rather easy to recognize, once known), in a started fight we talk about sudden signals (difficult to implement because they are diluted in a extremely short time, to learn to identify and react to them in time it takes a lot of training).
In the next treatments we will face a summary (with no pretense of completeness) of the signals collected over the centuries by the most ancient martial arts until the most recent studies of NLP.