Automatic doors are doors which open automatically when approached by someone, rather than needing to be opened manually with a door handle or bar. Automatic doors are powered open and closed, a door fitted with a spring to close it is not an automatic door. Automatic door is the application of advanced sensor technology, computer programmable control through the PLC and AC variable speed control system PLC control electromechanical actuators to open and close a door automatic door system. Automatic doors originated in the 20th century, 30 to 40 years, which was mainly used for military warehouse, an important plant for the fire, bullet-proof and easy to open the door. Designs for automatic doors vary. Some slide open, while others consist of panels which fold when people enter or exit, and others swing in or out like conventional doors. The doors are equipped with a motion sensor which can detect people when they approach, and the sensitivity of the sensor can be adjusted as needed. For people in wheelchairs and other disabled individuals, automatic doors are an immense boon, since conventional doors can be very hard to work with. It may be impossible to open a conventional door while seated in a wheelchair or navigating with crutches, for example, and for people with disabilities in their hands and arms, conventional doors can present a real obstacle. Automatic doors ensure disabled access into public facilities. These doors require electricity to operate, with electricity driving the motor which opens the doors. Many automatic doors have a manual override so that in the event of a power failure or a mechanical problem, the doors can still be opened. The doors are also designed to be sensitive to obstacles in the doorway, so that they will not close on someone or something which happens to be in the middle of the path of the doors. These safety measures ensure that automatic doors are safe in a variety of situations.