| 摘要 |
PROBLEM TO BE SOLVED: To prevent pop noise from being produced. SOLUTION: A master device 1 is instructed to perform switching between transmission and reception by using a transmission instruction signal line 31 which varies in DC level as the transmission switch 25 of a slave device 2a is operated and this interphone is equipped with a mute signal generating circuit 17 which sends mute signals 34 and 35 out for a given period when the level of the transmission instruction line 31 varies and a speaker driving circuit 16 which drives a speaker 21 set into reception mode by amplifying the voice signal outputted from a speaker 23 set into transmission mode and stops the amplifying operation when the mute signals 34 and 35 are sent out.
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