Network-connectable device and method for managing power thereof

1. A network-connectable device configured to communicate with a plurality of computer-related devices via a network, said network-connectable device comprising:

a list management unit configured to:

register the plurality of computer-related devices connected to the network-connectable device via the network on a list when the list management unit receives a start command signal instructing an activation of the network-connectable device transmitted from the plurality of computer-related devices via the network; and

delete each of the plurality of computer-related devices from the list when each of the plurality of computer-related devices registered on the list is switched to or is to be switched to a disconnected state from the network-connectable device; and

a shutdown unit configured to shut down power to a part of the network-connectable device when all of the plurality of computer-related devices connected to the network-connectable device via the network are deleted from the list.

2. The network-connectable device according to claim 1 , wherein the list management unit is configured to delete each of the plurality of computer-related devices from the list when each of the plurality of computer-related devices is shut down or is to be shut down.

3. The network-connectable device according to claim 1 , wherein the list management unit comprises a first determination/deletion unit configured to:

determine that at least one of the plurality of computer-related devices is to be switched to be disconnected from the network when the list management unit receives a disconnection notification signal transmitted from the at least one of the plurality of computer-related devices which indicates that the at least one of the plurality of computer-related devices is to be disconnected from the network; and

delete the at least one of the plurality of computer-related devices outputting the notification signal from the list.

4. The network-connectable device according to claim 1 ,

wherein the start command is periodically transmitted by each of the plurality of computer-related devices during operations thereof,

wherein the list management unit comprises a second determination/deletion unit configured to:

determine that at least one of the plurality of computer-related devices is switched to the disconnected state when the start command signal from the at least one of the plurality of computer-related devices registered on the list is not received over a predetermined time period; and

delete the at least one of the plurality of computer-related devices from the list.

5. The network-connectable device according to claim 1 , further comprising:

a power-on unit configured to turn on the power when at least one of the plurality of computer-related devices is registered on the list on which none of the plurality of computer-related devices have been registered.

6. The network-connectable device according to claim 1 , further comprising:

a motor as a drive source, wherein the shutdown unit is configured to shutdown the power to the motor.

7. The network-connectable device according to claim 6 , further comprising;

a storage device that comprises a data-recordable hard disk driven by the motor.

8. The network-connectable device according to claim 1 , further comprising:

a reproducing device configured to reproduce an image or a sound, wherein the shutdown unit is configured to shutdown the power to the reproducing device.

9. The network-connectable device according to claim 1 , wherein the plurality of computer-related devices comprise at least one of a desktop computer, a portable computer and a digital home electrical appliance.

10. The network-connectable device according to claim 1 , further comprising:

a first power source;

a second power source

a first unit operable on power supplied from the first power source;

a second unit operable on power supplied from the second power source, the second unit comprising the list management unit and the shutdown unit,

wherein the shutdown unit is configured to shut down the power from the first power source to the first unit.

11. A power management method for a network-connectable device configured to communicate with a plurality of computer-related devices via a network, said method comprising:

registering the plurality of computer-related devices connected to the network-connectable device via the network on a list when the network-connectable device receives a start command signal instructing the network-connectable device to activate which is transmitted from the plurality of computer-related devices via the network;

deleting each of the plurality of computer-related devices from the list when each of the plurality of computer-related devices registered on the list is switched to or is to be switched to a disconnected state disconnected from the network; and

shutting down power to a part of the network-connectable device when all of the plurality of computer-related devices connected to the network-connectable device via the network are deleted from the list.

12. A non-transitory computer-readable recording medium including computer program instructions, which when executed by a network-connectable device configured to communicate with a plurality of computer-related devices via a network, cause the network-connectable device to perform a power management method comprising:

registering the plurality of computer-related devices connected to the network-connectable device via the network on a list when the network-connectable device receives a start command signal transmitted from the plurality of computer-related devices via the network instructing the network-connectable device to activate;

deleting each of the plurality of computer-related devices from the list when each of the plurality of computer-related devices registered on the list is switched to or is to be switched to a disconnected state from the network; and

shutting down power to a part of the network-connectable device when all of the plurality of computer-related devices connected to the network-connectable device via the network are deleted from the list.

13. The network-connectable device according to claim 1 , wherein

the start command is periodically transmitted by each of the plurality of computer-related devices during operations, and

the list management unit comprises a determination/deletion unit, the determination/deletion unit including:

a selection unit configured to select one of the at least one of the plurality of computer-related devices registered on the list sequentially and cyclically, as a current target computer-related device;

a measurement unit configured to measure a time to, at which the network-connectable device previously received the start command signal from the current target computer-related device;

a processor configured to compute an elapsed time Δt from the time t 0 to a current time t 1 ; and

a deletion unit configured to delete the current target network-related device from the list when the elapsed time Δt becomes greater than a predetermined time period.