The older units usually use mechanical control with mechanical push buttons to select the mode of operation and fan speed control. Another rotary knob is used to set the desired temperature of the unit. This was the most cost effective and simplest method of control in the past.The development and the reduction in cost of electronic controls have enabled manufacturers to implement electronic control touch pad that comes with remote control. Some of the electronic controls that have been built into the system include:Timer Control where you will be able to set when to ON or OFF the unit.Mode control is operated by pushing the same button to select the mode of operation.Temperature setting is displayed by the use of 7 segment display and buttons used to change the settings.Energy saving feature such as sleep or economizer function where the set temperature will be automatically adjusted according to the duration that has elapsed.