The opening signal of an automatic door is the hub of the entire work process, and without it, automatic work cannot be completed. The opening signal of an automatic door is a contact signal, and microwave radar and infrared sensors are two commonly used signal sources. 

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Microwave radar induction uses the Doppler working principle to trigger the induction effect by sensing moving objects. Microwave radar has a fast response speed and a wider sensing range, making it suitable for places where people with normal walking speed pass through. Its characteristic is that once people near the door do not want to go out and remain stationary, the radar will no longer react, and the automatic door will close, providing a certain degree of protection for the door operator. The disadvantage of using a microwave sensor for an automatic door is that if people near the door do not want to move and remain stationary, the radar device will no longer send out signals, and the automatic door will naturally not have a switch action, so there is a possibility of people being trapped here.

Infrared sensors react to the presence of objects, regardless of whether personnel are moving or not, as long as they are within the scanning range of the sensor, they will react and send out contact signals. The disadvantage is that the reaction speed of infrared sensors is slow, which is suitable for places where people with slow movements enter and exit.

In addition, if the automatic door receives contact signals for too long time, the controller will consider the signal input system to be obstructed. Moreover, if the automatic sliding door remains open for too long, it can also cause damage to electrical components. Due to the fact that microwave radars and infrared sensors do not know whether people approaching automatic doors really want to enter, some situations may use button switches, foot switches, etc. as triggering device.