The Digital Addressable Lighting Interface (DALI) is a lighting control protocol that allows individual control and monitoring of each device in a lighting system (e.g. ballasts, emergency lighting etc), as well as groups of such devices. An improved DALI compliant Line Controller is described which may be advantageously used in a commercial setting. The sockets for both DALI lines and Ethernet are industry standard RJ45 sockets, allowing the use of industry standard cables (as compared to DB9 connectors which are not typically used in industrial settings). Further the use of RJ45 sockets enables the DALI controller to be SELV compliant, thus reducing the risk of electrical shock whilst working on the controller and advantageously providing a safer controller for use in an industrial environment. Additional modifications for use in an industrial environment include constructing DIN mountable slimline housing which extends along the DIN rail to minimise the footprint of the controller and increase packing efficiency on the rack, providing an externally accessible battery compartment on the top surface allowing quick and easy battery replacement without requiring removal of the controller from the DIN rack, and LED visual indicators on the top surface to provide status information and allow easy identification of a specific controller with a problem when mounted on a DIN rack with many other devices.