Abstract: A lighting device includes an LED light source (20) operable by electric power supplied to the device, and a control system (23) receiving electric power from an external power supply (26) and supplying power to the light source (20). The control system (23) also being operable of operating in a second mode to supply power to the light source (20) only on receipt by the control system (23) via the power supply (26) of a signal identifying said device. Thus the device (24) can be incorporated in a conventional lighting circuit or a circuit in which the devices (24) are individually controlled.