| 摘要 |
PURPOSE:To reduce a noise of demodulation at the receiving side in the communication of a vector sum drive linear prediction coding system by superposing a prescribed noise on a dual tone signal produced based on dial information. CONSTITUTION:A tone dialer 3 receives the dial information from a key pad 1-1 of a handset 1 via a dial detector means 2 and produces a prescribed dual tone signal. A VSELP shows an information quantity compression system which is premised on the human voices. Therefore a narrow band signal like the dual tone signal increases noises when it is decoded. In this respect, a noise superposing means 4 adds a white noise, for example, received from a noise source 4-1 to the dual tone signal and sends these superposed signals to a VSELP coding/decoding device 5. So that the increase of a band is prevented when the compression coding is performed.
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