Mode indicating lights and Mode selection buttons:

Mode indicating lights. Situated straightly below the manual push buttons, these lights denote the operating mode of the controller. While in manual mode, the left light, labeled "M", will be lit; while in the automatic mode, the right light, labeled "A" will be lit.

Mode selection buttons.  Situated straightly under each mode indicating light, every button will select its respective mode of control.   The controller will be in the manual mode of operation if the button below the "M" mode light is depressed; the controller will be in the automatic mode of operation if the button below the "A" mode light is depressed.

As previously discussed, a particular plant will possibly have controllers variant from the two described here.  While most information given could be commonly applied, it is extremely important in which the operator know the specific plant's controllers and their applications.