| 摘要 |
In a portable radio telephone powered by a removable rechargeable battery, a differential microphone having a first and a second microphone element is mounted. A front sound collecting hole is formed in the front of the casing of the telephone and includes the first microphone element. The front sound collecting hole constitutes a transmitter portion. A rear sound collecting hole is formed in a portion of the battery directly opposite in position to the front sound collecting hole. The rear hole is communicated by a passageway to a rear sound collecting portion included in the differential microphone. Speech and noise around the telephone are input to the front hole while only noise, which is opposite in phase to the noise input to the front hole, is input to the rear hole. As a result, the noise input to the front and rear holes cancel each other. The rear hole is formed in a portion of the battery where a space is present. When the rear hole is directly formed in a generating member included in the battery, the inner periphery of the generating member defining the hole is covered with a member made of resin. If desired, the rear hole may be implemented by a through hole, in which case the differential microphone will be inserted in the through hole.
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