| 摘要 |
PURPOSE:To improve the talking quality by using a voice level switching circuit operated at loudspeaker talking also for talking with a handset. CONSTITUTION:When a changeover switch 8 is switched to loudspeaker talking positions 4, 6, a transmission/reception attenuation control circuit 15 transmits a signal setting the attenuation to 30-35dB to a transmission/reception level comparator circuit 12. A transmission voice level entering from a microphone 6 and a reception voice level from a trunk line 1 are compared in this case to control the attenuation of attenuation circuits 13, 14 thereby switching transmission and reception and realizing a pseudo simultaneous loudspeaking talking. When the changeover switch 89 is thrown to the position of a handset 3, the control circuit 15 transmits a signal setting the attenuation to 6-10dB to the comparator circuit 12. A reception signal from the trunk line 1 is amplified and reaches the handset 3 through the attenuation circuit 13. When the transmission signal comes, the comparator circuit 12 becomes the transmission mode, the attenuation of the attenuation circuit 14 is 0 and a sufficient transmission signal is given to the trunk line 1. |
