| 摘要 |
PURPOSE:To use an electroacoustic transducer in common for a transmitter and a receiver, by taking the ratio of electric input and output of two electroacoustic elements at communication to discriminate transmission or reception from the ratio and controlling a channel. CONSTITUTION:One electroacoustic transducer T1 having two electroacoustic elements t, r, is mounted to an ear. In case of the transmission, currents I1, I2 is conducted to the transducing elements t, r, outputs et, er of amplifiers VII, VIIIproportional to the currents I1, I2 are inputted to an electronic circuit I, where the value of er/et=Ir, It is calculated and an electronic circuit II discriminates whether or not the value is equal to a value alpha0. When er/et=alpha0, the gain of the amplifier IV is increased and an input is given to a telephone circuit III. When er/etnot equal to alpha0, the gain of the amplifier V is increased, the gain of the amplifier IVis decreased and the voice of the receiver is transmitted to the ear. |
