The invention provides for a controller such as a thermostat for an air handler including a housing having a circuit board and a display screen, the display screen having at least one alpha-numeric icon and a group of touch sensitive areas having at least two displayable touch sensitive areas. A microprocessor provided for the display screen. A sole mechanical button or switch is mounted in the housing and the button has a first end and second end and a touch surface extending between the first end and second end. The sole mechanical button signals the microprocessor in order to adjust the alpha-numeric icon, so that the combination of inputs received by the microprocessor from the group of touch pad sensitive areas and sole mechanical button provide for each and every adjustment required for all of the operational functions of the controller. The mechanical button may be a rocker switch.