VOICE SWITCH CIRCUIT

摘要

PURPOSE:To prevent an SN ratio from deteriorating and to reduce the quantity of voice switch insertion loss by adapting a voice switch circuit for each of transmission channels of plural microphones. CONSTITUTION:A transmit voice signal inputted to one of the microphones 11-16 is amplified by a corresponding amplifier among 21-26 and inputted to a corresponding transmission insertion loss circuit among 41-46 and a voice switch control part 13. The voice switch control part 13 check whether transmit/ receive signals detected from signal branch terminals I1-I6 and I7 exceed a transmission threshold value and larger than the level of the receive signal or not and also compares the levels of the transmit/receive signals with one another. The transmission/reception state of voice switch loss to be controlled is decided and the number of transmission channels to be made effective is decided on the basis of the results of said check and comparison; and a loss control signal is outputted to control signal terminals phi1-phi7 according to both decision contents to set the quantities of the insertion loss circuits 41-46 and 9.