A luminaire comprising within the same a first lamp, one or more second lamps (12b, 12c, 12d) and a power supply circuit (10, 30a, 30b, 32) for supplying power to the first lamp and the one or more second lamps (12b, 12c, 12d), the one or more second lamps (12b, 12c, 12d) respectively comprising: - a transmitting circuit configured to transmit a signal comprising a message via a constrained signalling channel to a receiving circuit of the first lamp, wherein the one or more second lamps are configured to start the transmission of the signal; the luminaire being characterized in that: - the receiving circuit of the first lamp is configured to receive the one or more signals via the constrained signalling channel, wherein the receiving circuit is configured to receive at least a respective one of said signals from each of the one or more second lamps (12b, 12c, 12d) via said constrained signalling channel by detecting modulations in a current and/or voltage of the power supplied by said power supply circuit of the luminaire, wherein the constrained signalling channel comprises the power supply circuit (10, 30a, 30b, 32), propagation of the one or more signals thereby being constrained to the power supply circuit within the same luminaire as the first lamp and the one or more second lamps; and - the first lamp comprises a controller configured to detect, based on the reception of said one or more signals via said constrained signalling channel, that the one or more second lamps are present in the same luminaire as the first lamp, and to identify the one or more second lamps based on the reception of the message conveyed in each of the respective received signals. - a transmitting circuit configured to transmit a signal comprising a message via a constrained signalling channel to a receiving circuit of the first lamp, wherein the one or more second lamps are configured to start the transmission of the signal; the luminaire being characterized in that: - the receiving circuit of the first lamp is configured to receive the one or more signals via the constrained signalling channel, wherein the receiving circuit is configured to receive at least a respective one of said signals from each of the one or more second lamps (12b, 12c, 12d) via said constrained signalling channel by detecting modulations in a current and/or voltage of the power supplied by said power supply circuit of the luminaire, wherein the constrained signalling channel comprises the power supply circuit (10, 30a, 30b, 32), propagation of the one or more signals thereby being constrained to the power supply circuit within the same luminaire as the first lamp and the one or more second lamps; and - the first lamp comprises a controller configured to detect, based on the reception of said one or more signals via said constrained signalling channel, that the one or more second lamps are present in the same luminaire as the first lamp, and to identify the one or more second lamps based on the reception of the message conveyed in each of the respective received signals. - the receiving circuit of the first lamp is configured to receive the one or more signals via the constrained signalling channel, wherein the receiving circuit is configured to receive at least a respective one of said signals from each of the one or more second lamps (12b, 12c, 12d) via said constrained signalling channel by detecting modulations in a current and/or voltage of the power supplied by said power supply circuit of the luminaire, wherein the constrained signalling channel comprises the power supply circuit (10, 30a, 30b, 32), propagation of the one or more signals thereby being constrained to the power supply circuit within the same luminaire as the first lamp and the one or more second lamps; and - the first lamp comprises a controller configured to detect, based on the reception of said one or more signals via said constrained signalling channel, that the one or more second lamps are present in the same luminaire as the first lamp, and to identify the one or more second lamps based on the reception of the message conveyed in each of the respective received signals.