| 摘要 |
PURPOSE:To prevent oscillation even in transient state between transmitting and receiving state and to attain simultaneous calling precisely, by keeping the sum of transmitting attenuation and receiving attenuation at a constant value. CONSTITUTION:When a voice is inputted to a microphone input terminal 1 and transmitting state is kept, alternation switches 10, 14 are turned to the shown status and a transmitting system transmitting amplifier 8 and a receiving system attenuator 12 are connected to the transmitting system and receiving system respectively. When a receiving input (b) is increased larger than the input from the microphone input terminal 1 and switching control starts to operate, the alteration switches 10, 14 for transmission/reception switching are successively stepped down. In a call line to be switched by the step-like switching operation, a transmitting system transmitting attenuator 9 and a receiving system receiving amplifier 13 are connected to the transmitting system and the receiving system respectively, so that the sum of the transmitting attenuation and receiving attenuation can obtain optional constant characteristic even in the transient state by selecting appropriately resistance per one step of the alteration switches 10, 14. |
