The expansion module for access control communicates with the access control terminal or door station via the RS-485 bus and connects to the door detector, exit button, card reader, and lock. It can transmit card information, door opening information, and alarms to the access control terminal or door station, thereby enhancing the security of access control. It serves to expand access control functions by collaborating with the access control terminal and door station. It supports RS-485 communication. It can be connected to electronic or magnetic locks to increase security. It features three indicators to show whether the device is on or off, as well as the function and status of the door.