491– Relay Unit

The 491 Relay Unit is a DALI Stands for Digital Addressable Lighting Interface. Standardised digital protocol for lighting control, allowing communication between control devices and LIUs (control gear). mains switch, intended for installation inside luminaires or electrical cabinets.

Can be used with fixed output electronic ballasts, enabling them to be added to a DALI network.

A maximum load For example, dimmers, relay units, ballasts etc. Receives messages from control devices and performs the relevant action e.g. sets the lighting it controls to the relevant level. Some control may be possible at the device itself. Also known as Control Gear or LIU, see entries for both. of three Helvar ‘s’ series electronic ballasts may be connected.