| 摘要 |
PROBLEM TO BE SOLVED: To provide an interphone system with a slave set provided with a thin piezoelectric speaker giving no restriction to a housing design. SOLUTION: A cavity at one surface of a piezoelectric diaphragm 51 constituting the piezoelectric speaker to be used for the speaker of a slave set is tightly closed and a small slot for emitting sound 55 is provided at a cavity 54 at the other surface of the diaphragm 51 to eliminate an opening part (sound emitting surface) at the front surface of the speaker to eliminate the restriction in the housing design of the slave set.
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