Analog Controllers are usually designed to fit into a panel assembly as a slide in or out module. The front panel of an analog controller displays information for operators such as: measuring variables, error signals, output controller signal, and controller modes and parameters. It allows the adjustment of many parameters as the operator desires. The display is typically expressed in percentage of span . There often is a switch on the front panel by which the controller can be placed in a manual control mode, which means that the output can be adjusted independently of the input, using the operator settings. In automatic mode the controller is a function of the input using the presetting controller parameters. The controller often has the capability for the operator to select between different modes .