| 摘要 |
PURPOSE:To contrive the miniaturization of an amplifier circuit and an attenuation circuit, etc., and high reliability, by providing a code conversion circuit that transfers a PCM signal, converting the level of a sound signal represented by an input PCM signal corresponding to a control signal, and outputting it as the PCM signal of the sound signal with a different level. CONSTITUTION:A signal sent from an outside key telephone set, or exchange, is inputted to a code conversion circuit 2 as a PCM signal A through an outside interface circuit 1. The code conversion circuit 2 converts the level of sound represented by the PCM signal A, and outputs the PCM signal A' of the sound signal with the different level. In other words, the code conversion circuit 2 converts the level of the sound signal leaving it as the PCM signal. As for the degree of a level conversion, it is possible to select a value out of various kinds of values by setting a level setting parameter in advance at a control circuit 5. Thus, so that the signal level of the sound signal can be digitally selected, it is possible to miniaturize a circuit and to obtain the high reliability, and non-adjustment by adopting a digital type telephone set.
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