What is the principle of automatic fire door control?

What is the principle of automatic fire door control? The following is a brief description of Zonle Fire Door Factory and you:

For normally open fire doors, civil buildings are generally flat doors, a single fire door release switch and a single linkage module are installed, and a double door is equipped with two fire door release switches and two single linkage modules. After the smoke detectors on either side of the fire door detect smoke, they report to the fire alarm controller through the bus, and the linkage controller sends out action commands according to the existing settings. The single linkage module dedicated to the fire door receives the command, and the passive normally open contact of the module is closed, and the DC 24V coil loop of the fire door release switch is turned on. The coil is instantly energized to release the fire door, and the fire door is automatically closed by the elastic force of the door closer. The coil loop is automatically cut off when the fire door is disengaged from the release switch. At the same time, the auxiliary contact of the fire door release switch inputs the fire door status signal into the single linkage module, and then sends it to the fire control room through the alarm bus. The fire control room can also directly control the on-site linkage module to close the fire door through the bus, and get a confirmation feedback signal that the fire door is closed.