A method for controlling a digital television (30, 40, 212, 650, 750) located in a room of a hotel among a plurality of independent hotel rooms physically separated from one another in the hotel, wherein a compact wireless device serves as a room key, and wherein the DTV includes an access point card (131, 210, 311, 600, 700), the method comprising: wirelessly connecting the compact wireless device to the AP card; synchronizing data between the AP card and the compact wireless device, wherein the AP card includes a dual application that includes a first application used for communication with the compact wireless device and a second application used for communication with a general wireless device, and wherein the compact wireless device includes a third application corresponding to the first application of the AP card, the first and third application communicating without using MAC- and IP-associated protocols and a network of the first and third application is always maintained in an active status so as to synchronize the data between the first application and the third application; receiving, at the DTV (30, 40, 212, 650, 750), display type information from the compact wireless device, wherein the display type information is type information of data capable of being processed by the compact wireless device; transmitting, from the DTV (30, 40, 212, 650, 750), the received display type information to a management server; receiving, at the DTV (30, 40, 212, 650, 750), a data pair consisting of general additional information and additional information dependent on the display type information from the management server; and controlling the general additional information to be displayed on the DTV, and transmitting, from the DTV (30, 40, 212, 650, 750), the additional information dependent on the display type information to the compact wireless device, wherein the display type information corresponds to information capable of identifying at least one of an Audio/Video, A/V, signal output, an audio signal output, and a text signal output. wirelessly connecting the compact wireless device to the AP card; synchronizing data between the AP card and the compact wireless device, wherein the AP card includes a dual application that includes a first application used for communication with the compact wireless device and a second application used for communication with a general wireless device, and wherein the compact wireless device includes a third application corresponding to the first application of the AP card, the first and third application communicating without using MAC- and IP-associated protocols and a network of the first and third application is always maintained in an active status so as to synchronize the data between the first application and the third application; receiving, at the DTV (30, 40, 212, 650, 750), display type information from the compact wireless device, wherein the display type information is type information of data capable of being processed by the compact wireless device; transmitting, from the DTV (30, 40, 212, 650, 750), the received display type information to a management server; receiving, at the DTV (30, 40, 212, 650, 750), a data pair consisting of general additional information and additional information dependent on the display type information from the management server; and controlling the general additional information to be displayed on the DTV, and transmitting, from the DTV (30, 40, 212, 650, 750), the additional information dependent on the display type information to the compact wireless device, wherein the display type information corresponds to information capable of identifying at least one of an Audio/Video, A/V, signal output, an audio signal output, and a text signal output.