| 摘要 |
PURPOSE:To compensate the reduction of sensitivity of a carbon transmitter which is due to time change and to suppress the variation of a transmission level during the transmission of data by performing automatic gain control so that the original level is always kept even if the sensitivity is reduced in accordance with time change. CONSTITUTION:When a charge detecting circuit 19 detects the setting of a handset the detecting signal is applied to a control circuit 23. The control circuit 23 sets up the side tone level of the original transmitting carrier, i.e. the side tone level corresponding to the maximum sensitivity of the carbon transmitter 4. After passing the time for initialization, the control circuit 23 actuates an automatic gain controlling circuit 12 and controls the level of the transmitting signal so as to coincide with the original transmitting level. When the handset is removed, the control circuit 23 detects the removal by an output from the set detecting circuit 19 and all operation is restored. |
