The solution was a more advanced : the impulse relay with a "staircase" function .
What was needed was a logic —a set of rules for the electricity to follow. This was the birth of the . The Core Principle: Temporary Presence The logic is simple, elegant, and almost human: When a person requests light, provide it, but do not waste it. Assume they only need enough time to climb one flight of stairs. logi escalier
Mrs. Dupont goes down to get her mail. She presses the button on the 2nd floor, the light turns on for 60 seconds. She retrieves her mail and returns to the 2nd floor in 45 seconds. The light is still on. She enters her apartment. Fifteen seconds later, the timer ends, and the light turns off. The solution was a more advanced : the