| 摘要 |
PURPOSE:To prevent the disconnection of a word ending/beginning by calculating the AND of each output of the divide level of receiving level, the second comparator of a transmitting level and a pulse generating circuit and calculating the OR of the output of the first comparator to control the degree of amplification. CONSTITUTION:A level between a transmission and a reception is compared at a comparator 13 and by the trailing of the output, a pulse generating circuit 30 is triggered and a pulse is generated. At this time, when the reception is inputted, the divide level of the receiving level of a volume VR and the transmitting level are compared at a comparator 31 and the output of an AND circuit 32 becomes L at the dropping time t4 of the circuit 31 and the output of an OR circuit 33 keeps H until the time t4 and becomes L after that, and at the time t4, variable loss circuits 3 and 8 that are amplification means are switched from a transmitting state to a receiving state. Therefore, a receiving switching time is more quickened in the presence of the reception input than in the absence of it and word ending disconnection preventing period is shortened and the word biginning disconnection of the receiving signal is prevented.
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