Automatic doors are powered open and closed either by power, spring, or both. There are several methods by which an automatic door is activated:
- A detects traffic is approaching. Sensors for automatic doors are generally:
- A - e.g., a floor mat which reacts to the pressure of someone standing on it.
- An curtain or beam which shines invisible light onto sensors; if someone or something blocks the beam the door is triggered open.
- A which uses low-power microwave for the same effect.
- A remote sensor (e.g. based on infrared or radio waves) can be triggered by a portable , or is installed inside a vehicle. These are popular for garage doors.
- A is operated manually, perhaps after security checks. This can be a push button switch or a swipe card.
- The act of pushing or pulling the door triggers the open and close cycle. These are also known as power-assisted doors.
In addition to activation sensors automatic doors are generally fitted with safety sensors. These are usually an infrared curtain or beam, but can be a pressure mat fitted on the swing side of the door. The purpose of the safety sensor is to prevent the door from colliding with an object in its path by stopping or slowing its motion.