Control of the luminaires is via 2 flex7 plug-in sensor heads operating at PELV. The luminaires are automatically switched on when movement is sensed. After the room is vacated the luminaires switch off when the timeout period has elapsed.
The decision to install 2 (or more) sensor heads as opposed to 1 may be made simply because the room is too large to be covered effectively by 1. Alternatively, day to day use of the room may be such that occupants will be desk based for long periods meaning fine movements need to be detected to avoid luminaires switching off whilst the room is still occupied.
Installation time is dramatically reduced as everything plugs-in, meaning only the 4 conductors at the Distribution Box require on-site termination.
Note: emergency luminaires are tested via a hard-wired 230V key switch, often located in close proximity to the distribution board.