| 摘要 |
PROBLEM TO BE SOLVED: To prevent sound quality from deteriorated with a small scale configuration even when a large number of microphones are connected in cascade and to avoid a sound signal from being distorted even when a talker is resident at a close distance by providing a mixing amplifier to each microphone equipment. SOLUTION: The level of a speech signal from a pre-stage microphone equipment 4 received via an input terminal 10 is reduced up to a mixing level by a level matching circuit 6 through resistance voltage division. The speech signal from the level matching circuit 6 whose level is reduced and a microphone output speech signal are mixed by a mixing amplifier 4, which provides an output of the amplified speech signal. A microphone means is not required through the provision of the level matching circuit 6, the large sized equipment is avoided and the effect of amplifier noise is reduced. Since the transmission distance from an output terminal 9 of the speech signal till the mixing circuit is constant independently of the extension of the microphone equipment 4, a large number of microphone equipments are easily extended. |
