| 摘要 |
PURPOSE:To eliminate the need for manual pad setting and to carry out construction, reinstallation, alteration, etc., without any miss by inserting a pad circuit into a channel automatically when a speech current value is larger than a specific value. CONSTITUTION:The speech current flows through a DC synchro circuit 2 and is shunt to a resistance when flowing through a transistor(TR) 22, and a voltage drop corresponding to the speech current is generated across this resistance 33. When the voltage developed across the resistance 33 exceeds a certain value, a current flows to light emitting elements 72 and 34 and photodetectors turn on 71 and 81 and a TR 83 turns on to excite a relay 9, thereby inserting the pad circuit 4 into the channel. Consequently, a transmission level and a reception level are suppressed and side-tone characteristics are improved, so that clear speech characteristics are obtained. |
