Automatic sliding doors are ubiquitous in almost every mall and major store in the country. They can even be installed in homes. Here is how these doors work:
Usually, motion or optical sensors are mounted at the top of the doors. These sensors detect when people approach the doors and trigger them to slide open. Optical or motion sensors may also be placed within the frame of the door or just off to the sides.
Another kind of sensor is a weight sensor, which is usually installed in a mat placed just in front of the door.
In many cases, sensors are installed on both sides of the doors, allowing operation and entrance from either side.
The motion sensors are wired to a mechanism that opens and closes the doors. This mechanism has a clutch system attached to it that allows the doors operate. Usually, the doors are connected to a series of belts that are made of rubber.