| 摘要 |
PURPOSE:To obtain a door phone camera system in which a universal television receiver is used using a conventional door phone by providing a repeater having a light receiving element which receives an optical signal from a call tone receiver having a light emitting element which transmits the optical signal at a monitor device side. CONSTITUTION:A call tone is reported from a microphone 31 in a call signal receiver 24, and it is amplified, and is sound-detected, and a signal is generated with a signal generation means 35, and the optical signal is transmitted with a transmission means 36. The optical signal is received by a light receiving means 38 in a repeater 29, and is amplified at an amplification signal means 39, and is identified and detected at a detection means 40, and is controlled, then an indication is given to a switching circuit 42. The switching circuit switches an RF modulation signal from an outside with an RF signal from a camera 25 by a control indication means 41. Next, a video signal from the camera 25 is sent to the repeater 29 by a coaxial cable which connects a monitor device 26 and the camera 25. It is modulated with an RF modulation signal circuit 43 built in the repeater 29, and through the switching circuit 42, it is displayed on the screen of a television receiver in the monitor device 26.
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