Content display system and display device

A content display system comprising:

• a first control device which displays content on a display;
• a second control device which receives a voice;
• a third control device which generates a command corresponding to the voice received by the second control device, and determines whether the generated command is a change command to change first content being displayed on the display;
• and
• a fourth control device which distributes, to the first control device, second content corresponding to the change command when the third control device determines that the command is the change command, wherein
• the first control device changes a material being displayed on the display from the first content to the second content distributed by the fourth control device,
• when the voice received by the second control device includes authentication information to authenticate a user, the third control device adds the authentication information to the change command generated corresponding to the voice, and
• when the authentication information is not added to the change command, the first control device suspends display of the first content, displays the second content for a certain period of time, and displays the first content again in accordance with the first timetable when the certain period of time ends.