发明名称 |
Ring back tone transmission system |
摘要 |
In a digital and electronic switching apparatus, each subscriber's circuit is provided with a loop back circuit which selectively return a downward channel signal to an upward channel in order that a ring back tone informing a calling telephone set of the fact that a called telephone set is being dialed can be synchronized with a ringing tone dialing a called telephone set. Upon dialing a called subscriber, the loop back circuit is ON-OFF controlled in synchronism with the ON-OFF control of the ringing tone so that a tone signal generated from a common continuous ring back tone source can be transmitted to the loop back circuit and the calling telephone set via a speech path of a switching network.
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申请公布号 |
US4663759(A) |
申请公布日期 |
1987.05.05 |
申请号 |
US19850726650 |
申请日期 |
1985.04.24 |
申请人 |
HITACHI, LTD. |
发明人 |
MUKAEMACHI, TAKUJI;SHIRASU, HIROTOSHI;SUZUKI, TAIHEI |
分类号 |
H04M19/02;H04Q11/04;(IPC1-7):H04J3/12 |
主分类号 |
H04M19/02 |
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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