PROCESS CONTROLLER

PURPOSE:To perform bumpless switching of gain automatically by allowing controllers to perform the tracking operation of the output of a driver not only in a manual control mode but also at a non-selected time. CONSTITUTION:The output of a common operator 10 is inputted to a controller 20A through a contact (h) of an input tracking command changeover switch 40A and is inputted to a controller 20B through a contact (h) of a changeover switch 40B. When a gain selecting command 40 outputs a level ''1'' gain selecting command, switches 40A and 40B are switched to the contact (h) and a contact O (earth potential) and a switch 50 is switched to a contact A. When changover switches 40A and 40B are switched to contacts O, a tracking command is supplied to controllers 20A and 20B. Thus, controllers 20A and 20B different in gain are connected to the operator through said changeover switches 40A and 40B, and the mode of controllers 20A and 20B is switched to the tracking mode at a non-selected time to track the output of a driver 40.