Abstract: An electronic device includes an amplifier which is configured to amplify a sound signal and includes a vacuum tube including a heater configured to heat the vacuum tube; a voltage supply which is configured to supply a first voltage and a second voltage which is higher than the first voltage; and a controller which is configured to control the voltage supply to supply the second voltage to the heater in response to supply of a drive voltage to the amplifier being started and to supply the first voltage to the heater if the vacuum tube reaches a predetermined temperature.

Abstract: A sound output device is provided. The sound output device includes a vacuum tube for amplifying an audio signal; a power supply that supplies power to the vacuum tube; a first switch circuit that selectively connects the power supply to the vacuum tube; and a controller that controls the first switch circuit according to whether the vacuum tube is used.

Abstract: An electronic device includes an amplifier which is configured to amplify a sound signal and includes a vacuum tube including a heater configured to heat the vacuum tube; a voltage supply which is configured to supply a first voltage and a second voltage which is higher than the first voltage; and a controller which is configured to control the voltage supply to supply the second voltage to the heater in response to supply of a drive voltage to the amplifier being started and to supply the first voltage to the heater if the vacuum tube reaches a predetermined temperature.

Abstract: A docking station for docking of a plurality of portable media devices includes a main body, a plurality of accommodation units to accommodate the plurality of portable media devices, the plurality of accommodation units being provided in one side of the main body, and a plurality of docking ports to provide electrical connection between the plurality of portable media devices and the docking station, the plurality of docking ports being installed in the plurality of accommodation units, wherein each of the plurality of docking ports supports electrical connection between the docking station and any one of the plurality of portable media devices belonging to different product groups. Accordingly, a plurality of portable media devices belonging to different product groups is freely connected to one docking station to reproduce a sound signal, thereby improving user convenience.

Abstract: A sound output device is provided. The sound output device includes a vacuum tube for amplifying an audio signal; a power supply that supplies power to the vacuum tube; a first switch circuit that selectively connects the power supply to the vacuum tube; and a controller that controls the first switch circuit according to whether the vacuum tube is used.

Abstract: A device for synchronizing a power drive signal of a monitor, and a method therefor.

Abstract: An improved spot elimination circuit for a monitor capable of Display Power Management Signaling function prevents an occurrence of a focused beam spot from the phosphor screen of a cathode ray tube in the monitor by suddenly dropping the potential level of a high voltage. The circuit includes a high voltage generator, a X-ray sensor, a X-ray protector, a controller and a spot killer circuit. The spot killer circuit actuates the X-ray protector to virtually instantaneously shut down a high voltage generated from the high voltage generator in response to a logic signal indicative of absence of a vertical synchronizing signal. The controller determines the vertical sync signal and generates the logic signal. Accordingly, the phosphor screen of the cathode ray tube is protected from excessive cathode luminance at a focused spot which can cause degradation of the screen.