| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact portable telephone set, with which audio equipment to be used for the portable telephone set is made into only one earphone having a reversible microphone function, electric feedback is made into practically required -60 dB and that earphone is housed inside the portable telephone set and freely attachably and detachably supported. SOLUTION: While utilizing the characteristics of the earphone having the microphone function for making the electric feedback into -60 dB, a compressor and an extender are combined with a cancel circuit and further, the cord of that earphone is housed inside the portable telephone set so that the earphone cannot be disconnected from the portable telephone set.
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