发明名称 |
Handsfree unit |
摘要 |
The present invention provides a cheap handsfree unit which can prevent the howling phenomenon and reduce the input sound from the loud-speaker into the microphone in both the analog and digital modes. A reception side comprises a signal level adjusting circuit constituted by a switch circuit and attenuators, and a transmission side comprises a signal level adjusting circuit constituted by a switch circuit and attenuators, to introduce the attenuation of 15 dB or 30 dB in response to the analog or digital mode. A voice switch is constituted so that the analog reception signal and the analog transmission signal are rectified respectively by rectifiers, the levels of both signals are compared by a comparator, and either switch or switch having a higher input signal level becomes conductive as a result of the comparison. The attenuation is introduced on the basis of the communication mode, only to either the analog reception signal or analog transmission signal having a smaller signal intensity.
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申请公布号 |
US6154639(A) |
申请公布日期 |
2000.11.28 |
申请号 |
US19980199483 |
申请日期 |
1998.11.25 |
申请人 |
KABUSHIKI KAISHA TOSHIBA |
发明人 |
KANAZUMI, TAKUYA;KUROKAWA, OSAMU;ISHIKURA, AKIRA;NOMURA, YOSHIHIRO;HYODO, MASAKUNI;NAKAMURA, KEN |
分类号 |
H04B1/40;H04B1/46;H04B7/26;H04M1/60;H04M9/08;(IPC1-7):H04B1/40 |
主分类号 |
H04B1/40 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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