Being in control of who comes into or goes out of an area is access control. It’s common to have an access controller that is able to control the access through a specific door. This is outfitted with a keypad that allows people to interact with it.
This may be a keypad, a code system, or a combination of both. There is a door contact that is connected to the access controller. This lets the controller know whether the door is open or closed. There is also a strike pad that allows the controller to open the door when access to it has been granted.
These systems often let the person exit the area freely and without having to use a keycard or code. The key card that is used to gain access has an antenna in it as well as a chip. The antenna gives power to the chip so that the card doesn’t need its own power source. The card transmits a message in binary code to the keypad. The keypad then sends this to the access controller. The controller is the part of the system that grants or denies access- not the keypad. The keypad simply transmits the binary code.