| 摘要 |
PROBLEM TO BE SOLVED: To provide an intercom system for preventing good sleeps from being disturbed by ring tones at bedtime. SOLUTION: A house information board includes a timer. For example at 11 p.m., the gain of a variable amplifier circuit connected to a speaker is decreased or set to 0, or when a call is issued from a collective entrance unit after 11 p.m., the gain of the variable amplifier circuit connected to the speaker is decreased or set to 0. Further, no power is supplied to a display means in addition to a decrease in the gain of the variable amplifier circuit. COPYRIGHT: (C)2011,JPO&INPIT
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