发明授权
- 专利标题: Hands-free telephone
- 专利标题(中): 免提电话
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申请号: US313209申请日: 1989-02-21
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公开(公告)号: US4982425A公开(公告)日: 1991-01-01
- 发明人: Ikio Yoshida
- 申请人: Ikio Yoshida
- 申请人地址: JPX Tokyo
- 专利权人: NEC Corporation
- 当前专利权人: NEC Corporation
- 当前专利权人地址: JPX Tokyo
- 优先权: JPX63-33902 19880218; JPX63-252046 19881007
- 主分类号: H04M1/60
- IPC分类号: H04M1/60 ; H04M9/08 ; H04M9/10 ; H04Q7/20 ; H04Q7/38
摘要:
In order to perform voice-switched telephoning, a hands-free telephone includes a speaker, a microphone, a receive variable attenuator (R-ATT), a transmit variable attenuator (T-ATT), a receive signal detector, a transmit signal detector and an attenuation control circuit. The telephone also includes an auxiliary control circuit which prevents the output of the transmit signal detector from reaching the attenuation control circuit during a transient period between a call origination and the beginning of a conversation. During the transient period, only the speaker is enabled to output a ringback tone therethrough. When the output level of the transmit signal detector exceeds a predetermined level, the auxiliary control circuit passes the output of the transmit signal detector to the attenuation control circuit to start the voice-switched telephoning. Once the auxiliary control circuit passes the output of the transmit signal detector, it holds this state until the conversation finishes.
公开/授权文献
- US4513670A Teller machine enclosure 公开/授权日:1985-04-30
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