| 摘要 |
PROBLEM TO BE SOLVED: To complement a weak point of radio communication in an interphone system, having a slave unit connected to a master unit via wire, together with a sub-master unit connected via radio, while making the most of the merit of the radio communication. SOLUTION: In the interphone system handing images and voices, in addition to radio communication interfaces 29a, 39a in which the communication characteristics vary, depending on the difference of a communication environment including a communication distance and a building structure, even though the data rate is high, power line communication interfaces 29b, 39b are provided for other communication paths without dedicated signal lines. At installation or start of communication, each receiving side in control units 26, 36 decides on the communication quality from an image packet rate, the S/N ratio, etc., and transmits the decision result to the transmission side via the power line communication interfaces 29b, 39b, so that communication thereafter is performed via the radio, when the reception is proper; while the communication thereafter is performed via the power line, when the reception is not proper. COPYRIGHT: (C)2006,JPO&NCIPI
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