If you select this option, the GPIB interface acts as the System Controller. Because the System Controller in a GPIB system controls the GPIB Remote Enable (REN) and Interface Clear (IFC) lines, it maintains control over the GPIB. When you use the NI-488.2 software to control a GPIB system, the GPIB interface should normally be the System Controller. Some situations, however, such as a system with multiple controllers, require that the interface not be the System Controller. A GPIB interface acts as the System Controller by default.