| 摘要 |
PROBLEM TO BE SOLVED: To provide a video intercom system and intercom slave unit, wherein an unstable screen is prevented from being displayed, at a master unit side, without providing presence/absence of a camera for setting a slave unit connecting terminal. SOLUTION: In a slave unit Y without camera that does not include any camera, when a speech is started, an asynchronous signal generator 41 transmits a non-video signal. The non-video signal is different from a video signal that a slave unit X with camera transmits to a master unit Z, and has a higher frequency than that of a horizontal synchronizing signal and a vertical synchronizing signal (synchronizing signals) included in the video signal. Since the non-video signal is made into signal at a higher frequency than that of the synchronizing signals, even if noise is superimposed, the frequency is not reduced, thereby enabling identification as a non-video signal. In the master unit Z, by detecting the non-video signal, blue-back display is performed. COPYRIGHT: (C)2010,JPO&INPIT
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