Alternatives to the conventional wall-mounted switch are available or under development for more flexible switching arrangements. Automatic Control Where it is practical to control lighting automatically, various arrangements can be considered in terms of their cost effectiveness. Time clocks with over-ride facilities provide a relatively inexpensive method of securing some degree of control. More expensive, is a continuous-dimming system that in many circumstances is more acceptable to the occupants and saves more energy. In both daylight systems the luminaires are activated when daylight illuminance in the interior falls below a preset value and de-activated when sufficient daylight becomes available.
Security systems switch alarms and signals on when a space is illegally occupied.
This same technology can be adapted to switch artificial lights off when a space is unoccupied for a significant period of time. Concluding Remarks Conservation of lighting energy can be achieved by reducing power input and hours of use jointly. Reduction in power input can be achieved through the use of the Equivalent Sphere Illumination principle, although at present the facilities for measurement and calculation of ESI are not complete. By adhering to the simple principle that lights are 'ON' when required and 'OFF' when not, significant savings in total energy consumption can be realized. Optimized switching, automatic controls and advantageous use of daylight coupled with education and propaganda, can minimize hours of use.