Lighting system (1, 2, 3) comprising: a) a master unit (10, 20, 40), b) a plurality of slave units (15, 25, 26, 27, 45, 46, 47), wherein the slave units (15, 25, 26, 27, 45, 46, 47) c) are respectively designed to consume power by operating lighting means, d) are supplied by a common power supply unit provided in the master unit (10, 20, 40), e) can be provided with commands from the master unit (10, 20, 40), f) are respectively provided with a control unit which modulates the power consumption of the associated slave unit (15, 25, 26, 27, 45, 46, 47) according to a defined protocol, and g) wherein the master unit (10, 20, 40) is designed to measure the power consumed by all slave units (15, 25, 26, 27, 45, 46, 47); h1) wherein the slave units (15, 25, 26, 27, 45, 46, 47) are adapted to transmit a signal to the master unit (10, 20, 40) by modulating the power consumption according to the defined protocol, and h2) wherein the master unit (10, 20, 40) is adapted to recreate the signal from the measured power consumption of all slave units (15, 25, 26, 27, 45, 46, 47) according to the defined protocol, characterized in that the master unit (10, 20, 40) is adapted to transmit a command to all connected slave units (15, 25, 26, 27, 45, 46, 47) instructing all connected slave units (15, 25, 26, 27, 45, 46, 47) to increase or decrease their respective power consumption by a defined amount, wherein the control units of all connected slave units (15, 25, 26, 27, 45, 46, 47) are adapted to increase or decrease the power consumption of their respective slave unit (15, 25, 26, 27, 45, 46, 47) as instructed, and wherein the master unit (10, 20, 40) is adapted to determine a number of connected slave units (15, 25, 26, 27, 45, 46, 47) from a resulting change in total power consumption of all connected slave units (15, 25, 26, 27, 45, 46, 47). a) a master unit (10, 20, 40), b) a plurality of slave units (15, 25, 26, 27, 45, 46, 47), wherein the slave units (15, 25, 26, 27, 45, 46, 47) c) are respectively designed to consume power by operating lighting means, d) are supplied by a common power supply unit provided in the master unit (10, 20, 40), e) can be provided with commands from the master unit (10, 20, 40), f) are respectively provided with a control unit which modulates the power consumption of the associated slave unit (15, 25, 26, 27, 45, 46, 47) according to a defined protocol, and c) are respectively designed to consume power by operating lighting means, d) are supplied by a common power supply unit provided in the master unit (10, 20, 40), e) can be provided with commands from the master unit (10, 20, 40), f) are respectively provided with a control unit which modulates the power consumption of the associated slave unit (15, 25, 26, 27, 45, 46, 47) according to a defined protocol, and g) wherein the master unit (10, 20, 40) is designed to measure the power consumed by all slave units (15, 25, 26, 27, 45, 46, 47); h1) wherein the slave units (15, 25, 26, 27, 45, 46, 47) are adapted to transmit a signal to the master unit (10, 20, 40) by modulating the power consumption according to the defined protocol, and h2) wherein the master unit (10, 20, 40) is adapted to recreate the signal from the measured power consumption of all slave units (15, 25, 26, 27, 45, 46, 47) according to the defined protocol, the master unit (10, 20, 40) is adapted to transmit a command to all connected slave units (15, 25, 26, 27, 45, 46, 47) instructing all connected slave units (15, 25, 26, 27, 45, 46, 47) to increase or decrease their respective power consumption by a defined amount, wherein the control units of all connected slave units (15, 25, 26, 27, 45, 46, 47) are adapted to increase or decrease the power consumption of their respective slave unit (15, 25, 26, 27, 45, 46, 47) as instructed, and wherein the master unit (10, 20, 40) is adapted to determine a number of connected slave units (15, 25, 26, 27, 45, 46, 47) from a resulting change in total power consumption of all connected slave units (15, 25, 26, 27, 45, 46, 47).