Illumination system with automatic adaptation to daylight level

An illumination system comprising:

• at least one light source;
• a controller for controlling the power output of the at least one light source;
• a light sensor wirelessly communicating with the controller;
• the controller being capable of operating
• in a normal mode, in which the controller is configured to control the at least one light source such that a light level remains substantially constant, and
• in a change mode, in which the controller is configured to control the at least one light source such that the light level is gradually changed with a predetermined change rate (R) so as to decrease a deviation from a target level (LT), the controller being configured to switch from the normal mode to the change mode in response to one or more input signals received from the light sensor;
• wherein the light sensor comprises a memory containing data defining at least one characteristic of the behaviour of the controller and is configured to intermittently measure the light level, and determine whether or not to communicate a signal to the controller based on the measured light level and the data contained in the memory, the light sensor being configured to refrain from transmitting the signal when receiving the signal does not cause the controller to change the behaviour of the controller,
• wherein the sensor has information defining a predetermined upper margin (LU) higher than the target level (LT) and defining a predetermined lower margin (LL) lower than the target level (LT);
• and wherein the sensor in a first mode is designed to refrain from transmission if the measured light level is between the upper margin (LU) and the lower margin (LL).