| 摘要 |
PROBLEM TO BE SOLVED: To provide an alarm with a structure facilitating to switch over antenna directivity after installation. SOLUTION: The alarm includes: the antennas 7-1 to 7-n different in directivity; and a communication circuit 22 placed on a circuit board 2 and performing radio communication. An antenna switching part 21 is arranged, which selects one of the antennas 7-1 to 7-n and performs electric connection with respect to the communication circuit 22, thereby enabling to switch over to the antenna with most excellent sensitivity in the alarm after installation. COPYRIGHT: (C)2009,JPO&INPIT
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