| 摘要 |
PURPOSE:To perform a multi-call with high speech quality, by providing a detecting means which detects the fact that the count value of a digital type adder which adds plural voice signals arrives at a prescribed value, and providing a control means which operates an attenuator for a prescribed time according to a detected output. CONSTITUTION:The detecting means 6 which detects the fact that the count values of the adders 3A-3C arrive at the prescribed values is provided, and an attenuation control means 9 which operates the attenuator for the prescribed time according to the detected output of the detecting means 6 is provided. Thereby, it results that the adders 3A-3C are provided with the role of a level detector which represents a signal level after addition. Therefore, it is possible to control attenuation means 7 and 8 corresponding to the signal level after the addition, and to operate the attenuation means 7 and 8 only when an input signal exceeds a prescribed level. In such a way, it is possible to prevent a case where the count values of the adders 3A-3C exceed regulated number of digits, that is, overflow from being generated, and to prevent the distortion of an output voice due to the overflow from being generated.
|
