Messaging from the wake world to the sleep world works in principle as follows. A stimulus, for instance a blinking light, is presented to a sleeping and dreaming person. A message is coded into the stimulus using a coding scheme, for example the Morse code (see below). The stimulus gets incorporated into the dream, and is detected there by the dreaming person. The dreamer stays asleep and becomes conscious and aware of his sleeping and dreaming state by the stimulus, or was already aware of it before the stimulus incorporation. Finally, the dreamer decodes the message contained in the stimulus whilst still staying asleep.
Messaging from the sleep world to the wake world works very similar. The sleeping person selects a part or a physiological parameter of his wake world body which can be altered from within a dream, for instance the line of gaze of his eyes. The dreamer then again uses a coding scheme (which does not necessarily have to be the same as for the messaging from wake world to sleep world) and encodes a message into the body state alteration – short: gives a “body signal”. In the wake world, the body signal is recorded, in this case for example by an EOG, and decoded by hand or by a machine.