| 摘要 |
PURPOSE:To contrive to improve the transmission characteristic to a voice signal and a MODEM signal by switching a coding algorithm to an optimum algorithm depending whether an input signal is the voice or the MODEM signal. CONSTITUTION:The voice signal coding means 1 having the 1st algorithm, a MODEM signal coding means 33 having the 2nd algorithm, means 32, 34 switching both the algorithms in the unit of frames and a means 31 adding the information (1 bit) to identify the coding algorithm for each frame are provided and when a tone signal input of a prescribed frequency representing the start of MODEM signal transmission is detected, the algorithm is switched to the MODEM algorithm and when a silence signal period of a prescribed length is detected, the algorithm is switched back into the voice algorithm and the same algorithm as the preceding frame is used in other cases. Since the coding algorithm is switched depending whether input signal is the voice or the MODEM signal in this way, the transmission characteristic for the both is improved.
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