A lamp is provided that is controlled by messages transmitted via a network. The lamp has an internal memory that stores an address and an internal control circuit that responds to received messages that refer to this address. The address is updated when the lamp is installation in a power supply socket, using for example an address from the first message that is transmitted after installation. The lamp contains a detector that detects disconnection of the lamp from the power supply socket, for example by monitoring a resistance value between two parts of one of the power supply terminals of the lamp. In response to this detection the control circuit of the lamp sets information that enables an update of the address in the memory. When it is detected that the lamp is again connected to a power supply socket the address is updated on condition that the update is enabled.