Abstract: Proposed is a device for supplying emergency power to a digital door lock, which supplies emergency power by switching a connection method of a battery holder provided in the digital door lock from parallel to series or series to parallel by rotating a door lock opening/closing means.

Abstract: Disclosed is a method of exchanging information with an external device. The method includes: receiving information about one or more applications installed in the external device from the connected external device, listing and displaying a GUI corresponding to the application on a screen according to the information about the application, transmitting a control request for the application corresponding to a user input for the GUI to the external device, and receiving control command information according to the control request from the external device and applying a control command.