| 摘要 |
PROBLEM TO BE SOLVED: To adjust the volume of receiving voice which is sounded with a speaker, depending on the distance between the visitor near the entrance and the speaker of an entrance slave set. SOLUTION: In the entrance slave set 1 capable of paging a master set 2 to make a call, a control section 21 controls a current varying section 18 to vary the current to be supplied through an infrared illuminating lamp 17 from a slave set power source section 10, thereby changing an illumination distance of the lamp 17. Also, an infrared ray receiving section 19 of the slave set 1 is turned on by allowing an infrared ray emitted from the lamp 17 and reflected on the visitor to be incident. The section 21 detects the distance between the visitor and the speaker 14 on the basis of the timing for the section 19 to be turned on and the control timing of the section 18, and a volume changing section 20 is controlled according to this distance. In this way, the volume of the receiving voice which is sounded from the speaker is the optimum volume with which the visitor can listen comfortably. COPYRIGHT: (C)2003,JPO
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