Display device and play-back device having respective first and second interfaces

1. A display device to receive video information transmitted from a playback device and to display the video information, comprising:

a first interface to communicate information with the playback device;

a second interface to communicate information with the playback device; and

a display circuit to display video information received by the first interface or the second interface, wherein the display device transmits a first connection confirmation signal to confirm connection, via the first interface to the playback device and receives a response signal in reply to the first connection confirmation signal,

transmits a second connection confirmation signal to confirm connection, via the second interface to the playback device and receives a response signal in reply to the second connection confirmation signal, and

makes a function to use the first interface and the second interface between the display device and the playback device available if the response signal in reply to the first connection confirmation signal and the response signal in reply to the second connection confirmation signal are received,

and wherein if an interval of time between when the response signal is received in reply to the first connection confirmation signal and when the response signal is received in reply to the second connection confirmation signal is within a predetermined time range, it is judged that the function to use the first interface and the second interface is available.

2. A display device to receive video information transmitted from a playback device and to display the video information, comprising:

a first interface to communicate information with the playback device;

a second interface to communicate information with the playback device; and

a display circuit to display video information received by the first interface or the second interface, wherein the display device transmits a first connection confirmation signal to confirm connection, via the first interface to the playback device and receives a response signal in reply to the first connection confirmation signal,

transmits a second connection confirmation signal to confirm connection, via the second interface to the playback device and receives a response signal in reply to the second connection confirmation signal, and

judges that the playback device is connected via the first interface and the second interface to the display device if an interval of time between when the response signal is received in reply to the first connection confirmation signal and when the response signal is received in reply to the second connection confirmation signal is within a predetermined time range.

3. The display device according to claim 2 , wherein the predetermined time range is 1 msec±1 msec to 20 msec to 1000 msec±1 msec to 20 msec.

4. A playback device to play back video information and to transmit the video information to a display device, comprising:

a playback section to play back video information;

a first interface to communicate information with the display device; and

a second interface to communicate information with the display device, wherein the playback device transmits a first connection confirmation signal to confirm connection, via the first interface to the display device and receives a response signal in reply to the first connection confirmation signal,

transmits a second connection confirmation signal to confirm connection, via the second interface to the display device and receives a response signal in reply to the second connection confirmation signal, and

makes a function to use the first interface and the second interface between the playback device and the display device available if the response signal in reply to the first connection confirmation signal and the response signal in reply to the second connection confirmation signal are received,

and wherein if an interval of time between when the response signal is received in reply to the first connection confirmation signal and when the response signal is received in reply to the second connection confirmation signal is within a predetermined time range, it is judged that the function to use the first interface and the second interface is available.

5. A playback device to play back video information and to transmit the video information to a display device, comprising:

a playback section to play back video information;

a first interface to communicate information with the display device; and

a second interface to communicate information with the display device, wherein the playback device transmits a first connection confirmation signal to confirm connection, via the first interface to the display device and receives a response signal in reply to the first connection confirmation signal,

transmits a second connection confirmation signal to confirm connection, via the second interface to the display device and receives a response signal in reply to the second connection confirmation signal, and

judges that the display device is connected via the first interface and the second interface to the playback device if an interval of time between when the response signal is received in reply to the first connection confirmation signal and when the response signal is received in reply to the second connection confirmation signal is within a predetermined time range.

6. The playback device according to claim 5 , wherein the predetermined time range is 1 msec±1 msec to 20 msec to 1000 msec±1 msec to 20 msec.