Referring back to the paths 141 and 142 in FIG. 1, when the sensor of luminaire 101 detects movement and/or the presence of a user, the communications module of luminaire 101 transmits an indication message that contains an identifier of the transmitting luminaire and carries the information that the sensor of the transmitting luminaire has detected movement and/or the presence of a user. The last-mentioned information may be simply the mere occurrence of the transmission, but for the purpose of more flexible communications and possible future extensions it may be advantageous to define some information elements like codes or parameter values that, when included in an indication message, tell the receiving luminaires more exactly what made the transmitting luminaire emit the transmission.

At least the closest other luminaires, but possibly even all other luminaires of the lighting system, receive the indication message from luminaire 101. If the user moves along one of the paths 141 or 142, soon thereafter also the sensor of luminaire 102 detects movement and/or the presence of a user. As a response the communications module of luminaire 102 transmits an indication message, which is received by the other luminaires. Assuming that the user follows path 141, the same happens to luminaire 112 and then to luminaire 113.