Direct digital control (DDC) is also referred to a building automation systems (BAS) or energy management systems (EMS). In large commercial buildings DDC is used extensively to control HVAC equipment and electrical lighting and machinery necessary to commercial buildings. DDC is a control system along with an energy management system that saves money in energy dollars for building managers. From control of equipment to scheduling lighting and equipment usage to trending data for information collection DDC is essential for good energy management of large commercial buildings. DDC Systems allow for remote control and automatic computer control of systems including lighting and mechanical systems. For example, the lighting in an office building can be automatically set to turn off at 8 pm when no one is in the office. Just in case some is in the office the system will override the off sequence for rooms they occupy for 4 or 5 hours simply by the occupant turning the switch on.