| 摘要 |
PROBLEM TO BE SOLVED: To provide a voice encoding device which enables a user to normally hear a ring-back tone. SOLUTION: Two efficient voice encoding devices 11' and 12' which have trunk lines 31 and 32 stored in an exchange 2 and face each other with a trunk path between them insert a prescribed synchronizing signal and a control signal to the output signal to each other through the exchange by a synchronous control insertion part 104, and a synchronous detection part 105 turns on the control signal upon detecting the synchronizing signal. Meanwhile, a first rate conversion part 103 adds an ineffective signal, which increases the bit rate to allow intra-exchange transparent transmission, to an efficiently encoded voice signal from trunk lines, and a second rate conversion part 106 deletes this ineffective signal. When the synchronizing signal is detected and the control signal is turned on, selectors 107 and 108 bypass an encoding part 101 and a decoding part 102 through these rate conversion parts.
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