| 摘要 |
PROBLEM TO BE SOLVED: To enable a person at home to surely check who a visitor is without opening a door. SOLUTION: The visitor preliminarily installs a receiver 3 which performs a receiving operation in response to an electric wave signal generated by the visitor 1 on the indoor side (for example, inside the door 5 and at a wall in the entrance) of a visiting place, operates the receiver 3 in the entrance and makes the person at home understand that the visitor must be the person who preliminarily installs the receiver 3 by operating an electric wave signal generator 2 in front of the door 5 of the visiting place in visit later. COPYRIGHT: (C)2007,JPO&INPIT
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