| 摘要 |
PURPOSE:To reduce malfunction due to sound coupling of a microphone and a speaker and to decrease places that require adjusting by detecting sequence of voice input/output signals and changing transmitting state and receiving state. CONSTITUTION:When the signal level of a microphone 1 is above a set value in a detection comparator circuit 15, a high level detection signal is outputted at a point (a). At this time, if output (b) of a detection comparator circuit 14 and output (c) of a detection comparator circuit 15 are low level, it is judged as transmitting state by a sequence detecting circuit 17, and a switch 3 is turned on and a switch 6 is turned off by a switch circuit 12 and the unit is made to transmitting state. When there is input from receiving terminal, the switch 3 is turned off and the switch 6 is turned on by the detection comparator circuit 15 etc., and the unit is made to receiving state. |
