| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the need for preparing two kinds of power supply adapters even in a video entryphone system having an extension monitoring master, and to eliminate the need for using the power supply adapter having larger capacity. SOLUTION: An image bus controller 4 supplies power to a door unit 1 with a camera, a monitoring master 2, and the extension monitoring master 3 each. When installing an extension monitoring master, a sub-extension power supply adapter 6, being the same as the main power supply adapter 5 already used, is installed and connected in the image bus controller 4. The image bus controller 4 has a power supply detection circuit 47 for detecting the power supply adapters for subextension and a power supply switching circuit 45. The power supply switching circuit 45 supplies power by dividing the power to the image bus controller, the door unit with a camera, the monitoring master, and the extension monitoring master from the main power supply adapter and the power supply adapter for subextension used before extension when the power supply adapter for extension is detected in the power detection circuit. COPYRIGHT: (C)2004,JPO
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