| 摘要 |
PROBLEM TO BE SOLVED: To provide an intercom system capable of securing accuracy for detecting the number of sub-master units even in case of including the sub-master units supplied with power through signal lines. SOLUTION: A stand-alone sub-master unit 2a includes a current lead 26 connected between signal lines L. A master unit 1 includes a power feed 15 for outputting power to a power reception unit 25 of a power-receiving sub-master device 2b, a current detector 17 for detecting the current output from the power feed 15, and a control unit 13 for detecting the number of sub-master deices 2a, 2b connected to the signal lines L, based on the output from the current detector 17. Since the number of sub-master devices 2a, 2b is detected based on the current output from the power feed 15, differently from the case of detecting the number of units of the sub-master devices 2a, 2b based on the voltage between the signal lines L, the detection accuracy of the number of sub-master units 2a, 2b is secured. COPYRIGHT: (C)2007,JPO&INPIT
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